WEBVTT 00:00:00.000 --> 00:00:02.640 align:middle line:84% The following content is provided under a Creative 00:00:02.640 --> 00:00:04.000 align:middle line:90% Commons license. 00:00:04.000 --> 00:00:06.400 align:middle line:84% Your support will help MIT OpenCourseWare 00:00:06.400 --> 00:00:10.080 align:middle line:84% continue to offer high-quality educational resources for free. 00:00:10.080 --> 00:00:13.320 align:middle line:84% To make a donation or view additional materials 00:00:13.320 --> 00:00:17.280 align:middle line:84% from hundreds of MIT courses, visit MIT OpenCourseWare 00:00:17.280 --> 00:00:19.682 align:middle line:90% at ocw.mit.edu. 00:00:19.682 --> 00:00:21.640 align:middle line:84% DIEDRE TOOLE: Today, this is going to basically 00:00:21.640 --> 00:00:23.160 align:middle line:90% be an introduction to-- 00:00:23.160 --> 00:00:24.480 align:middle line:90% AUDIENCE: Introduce yourself. 00:00:24.480 --> 00:00:25.020 align:middle line:90% DIEDRE TOOLE: What? 00:00:25.020 --> 00:00:25.520 align:middle line:90% Oh. 00:00:25.520 --> 00:00:26.800 align:middle line:90% I'm Diedre Toole. 00:00:26.800 --> 00:00:29.503 align:middle line:84% I'm in the marine chemistry and geochemistry department. 00:00:29.503 --> 00:00:30.920 align:middle line:84% And today, I'm going to be talking 00:00:30.920 --> 00:00:33.240 align:middle line:84% about atmosphere-ocean interactions. 00:00:33.240 --> 00:00:36.280 align:middle line:84% And just kind of as a caveat, when we start all this, 00:00:36.280 --> 00:00:40.320 align:middle line:84% this is going to very much be an introduction of terms 00:00:40.320 --> 00:00:42.920 align:middle line:84% and concepts that you're likely to hear over 00:00:42.920 --> 00:00:44.720 align:middle line:90% the next couple of years. 00:00:44.720 --> 00:00:48.280 align:middle line:84% There's going to be a lot of overview-ish feeling to this. 00:00:48.280 --> 00:00:50.320 align:middle line:84% So what I'm going to talk to at first 00:00:50.320 --> 00:00:53.380 align:middle line:84% is a little bit of overview of what you did. 00:00:53.380 --> 00:00:54.600 align:middle line:90% I think it was lecture 4. 00:00:54.600 --> 00:00:57.400 align:middle line:84% It was lecture 4 when we talked about atmospheres 00:00:57.400 --> 00:00:58.513 align:middle line:90% and the composition. 00:00:58.513 --> 00:01:00.930 align:middle line:84% And then we're going to talk about aerosols and greenhouse 00:01:00.930 --> 00:01:04.250 align:middle line:84% gases and their different roles in the radiation budget. 00:01:04.250 --> 00:01:07.330 align:middle line:84% We're going to talk a little bit about UV radiation and ozone. 00:01:07.330 --> 00:01:09.850 align:middle line:84% And I'm going to show you an example of the polar ozone 00:01:09.850 --> 00:01:11.153 align:middle line:90% hole over Antarctica. 00:01:11.153 --> 00:01:13.570 align:middle line:84% And then we're going to do some examples that specifically 00:01:13.570 --> 00:01:14.870 align:middle line:90% affect on the ocean. 00:01:14.870 --> 00:01:17.210 align:middle line:84% We're going to look at sulfur cycling and dust 00:01:17.210 --> 00:01:19.770 align:middle line:84% and how that translates to iron delivery, 00:01:19.770 --> 00:01:21.450 align:middle line:84% a little bit on acid rain, and then just 00:01:21.450 --> 00:01:23.490 align:middle line:84% a little bit on halogen chemistry and sea salt 00:01:23.490 --> 00:01:24.030 align:middle line:90% particles. 00:01:24.030 --> 00:01:27.610 align:middle line:84% Just so you are aware that they exist. 00:01:27.610 --> 00:01:30.857 align:middle line:84% So I know this is an overview because you had it in lecture 4, 00:01:30.857 --> 00:01:32.690 align:middle line:84% but I just wanted to touch on it because I'm 00:01:32.690 --> 00:01:34.398 align:middle line:84% going to be using these terms a lot today 00:01:34.398 --> 00:01:36.530 align:middle line:84% and make sure we're on the same page. 00:01:36.530 --> 00:01:40.255 align:middle line:84% So this is the temperature structure of the atmosphere. 00:01:40.255 --> 00:01:41.630 align:middle line:84% This is the surface of the Earth. 00:01:41.630 --> 00:01:43.850 align:middle line:84% This is the height in kilometers. 00:01:43.850 --> 00:01:46.850 align:middle line:84% And pretty much today I'm going to be focusing primarily 00:01:46.850 --> 00:01:49.250 align:middle line:84% on the troposphere and the stratosphere 00:01:49.250 --> 00:01:53.490 align:middle line:84% because probably 50% of the mass in the atmosphere 00:01:53.490 --> 00:01:56.050 align:middle line:90% is below maybe five kilometers. 00:01:56.050 --> 00:01:59.360 align:middle line:84% And then a good 90% is below maybe 30 kilometers. 00:01:59.360 --> 00:02:01.220 align:middle line:84% So in terms of the gases and aerosols 00:02:01.220 --> 00:02:02.595 align:middle line:84% that we're interested in, they're 00:02:02.595 --> 00:02:04.660 align:middle line:90% pretty much in those layers. 00:02:04.660 --> 00:02:06.700 align:middle line:84% So what your atmospheric structure consists of 00:02:06.700 --> 00:02:08.860 align:middle line:90% is you have a boundary layer. 00:02:08.860 --> 00:02:10.660 align:middle line:90% It's about a kilometer thick. 00:02:10.660 --> 00:02:13.800 align:middle line:84% And on top of that is this region known as the troposphere. 00:02:13.800 --> 00:02:16.020 align:middle line:84% And it's about 10 kilometers thick. 00:02:16.020 --> 00:02:20.580 align:middle line:84% And it's heated from the bottom by IR radiation 00:02:20.580 --> 00:02:21.840 align:middle line:90% being emitted by the Earth. 00:02:21.840 --> 00:02:24.680 align:middle line:84% So it has an inverted temperature structure. 00:02:24.680 --> 00:02:27.552 align:middle line:84% So it's a region of really strong vertical mixing. 00:02:27.552 --> 00:02:29.760 align:middle line:84% And so if you're a particular particle in that layer, 00:02:29.760 --> 00:02:32.140 align:middle line:84% you can traverse the entire layer probably 00:02:32.140 --> 00:02:33.980 align:middle line:90% on the order of a couple days. 00:02:33.980 --> 00:02:36.160 align:middle line:84% Or if you're in the middle of a huge tropical storm, 00:02:36.160 --> 00:02:39.780 align:middle line:90% you could do it in an hour. 00:02:39.780 --> 00:02:42.180 align:middle line:84% Also, on top of that, we have the stratosphere. 00:02:42.180 --> 00:02:46.380 align:middle line:84% It's very thermally stable because of warming at the top, 00:02:46.380 --> 00:02:49.820 align:middle line:84% and that's primarily due to ozone absorbing, 00:02:49.820 --> 00:02:52.380 align:middle line:84% the photons coming from the sun, and a little bit of oxygen 00:02:52.380 --> 00:02:54.060 align:middle line:90% photolysis. 00:02:54.060 --> 00:02:56.860 align:middle line:84% But because of this structure it's very stable. 00:02:56.860 --> 00:02:59.960 align:middle line:84% So it's very weak in terms of vertical mixing. 00:02:59.960 --> 00:03:03.840 align:middle line:84% There isn't a lot of mixing going on. 00:03:03.840 --> 00:03:08.720 align:middle line:84% The tropopause is the break, this artificial boundary, 00:03:08.720 --> 00:03:10.330 align:middle line:90% between the two levels. 00:03:10.330 --> 00:03:12.080 align:middle line:84% And it actually is really important for us 00:03:12.080 --> 00:03:16.600 align:middle line:84% because there's a huge gradient there in terms of concentrations 00:03:16.600 --> 00:03:18.760 align:middle line:84% for the size or the chemical nature 00:03:18.760 --> 00:03:20.580 align:middle line:90% or the sources of the aerosols. 00:03:20.580 --> 00:03:23.960 align:middle line:84% And they are pretty well defined from one another 00:03:23.960 --> 00:03:25.760 align:middle line:90% in terms of transport. 00:03:25.760 --> 00:03:28.460 align:middle line:84% There is some transport across the tropopause. 00:03:28.460 --> 00:03:31.560 align:middle line:84% Like I said, you can have those massive clouds, 00:03:31.560 --> 00:03:33.180 align:middle line:84% massive thunderstorms in the tropics, 00:03:33.180 --> 00:03:36.400 align:middle line:84% and you can inject things up into the stratosphere. 00:03:36.400 --> 00:03:39.560 align:middle line:84% You also have some large-scale transport 00:03:39.560 --> 00:03:41.840 align:middle line:84% that ascents in the tropics because that's where 00:03:41.840 --> 00:03:43.960 align:middle line:90% the tropopause is the coldest. 00:03:43.960 --> 00:03:46.840 align:middle line:84% So you have air going up in the tropics 00:03:46.840 --> 00:03:50.480 align:middle line:84% and sort of in a large scale coming down in the poles. 00:03:50.480 --> 00:03:55.370 align:middle line:84% There's also a couple other, such as tropopause folding. 00:03:55.370 --> 00:03:58.510 align:middle line:84% It's a lot like how an eddy forms in the Gulf stream. 00:03:58.510 --> 00:04:01.690 align:middle line:84% It'll inject a little bit of air from the stratosphere 00:04:01.690 --> 00:04:03.410 align:middle line:84% into the troposphere, and that eventually 00:04:03.410 --> 00:04:05.730 align:middle line:84% gets entrained because of all the mixing there. 00:04:05.730 --> 00:04:08.570 align:middle line:84% But for the most part, it's a very slow leak 00:04:08.570 --> 00:04:10.290 align:middle line:90% from one level to the other. 00:04:10.290 --> 00:04:11.930 align:middle line:84% So it's really important to understand 00:04:11.930 --> 00:04:13.570 align:middle line:84% the chemistries and the two different areas 00:04:13.570 --> 00:04:14.770 align:middle line:90% because they really are just-- 00:04:14.770 --> 00:04:15.437 align:middle line:90% AUDIENCE: Hello? 00:04:15.437 --> 00:04:16.329 align:middle line:90% [INAUDIBLE]? 00:04:16.329 --> 00:04:18.185 align:middle line:84% Are you going to post this PowerPoint? 00:04:18.185 --> 00:04:20.310 align:middle line:84% Or should we be trying to scribble everything down? 00:04:20.310 --> 00:04:20.490 align:middle line:90% DIEDRE TOOLE: Oh, no. 00:04:20.490 --> 00:04:21.995 align:middle line:84% I'm going to post the PowerPoint-- 00:04:21.995 --> 00:04:22.870 align:middle line:90% AUDIENCE: OK, thanks. 00:04:22.870 --> 00:04:26.170 align:middle line:84% DIEDRE TOOLE: --right after class. 00:04:26.170 --> 00:04:29.955 align:middle line:90% So these are kind of the-- what? 00:04:29.955 --> 00:04:30.830 align:middle line:90% AUDIENCE: Never mind. 00:04:30.830 --> 00:04:35.610 align:middle line:84% DIEDRE TOOLE: [LAUGHS] This is kind of the atmosphere ocean 00:04:35.610 --> 00:04:39.490 align:middle line:84% interactions in a nutshell, the way I see it. 00:04:39.490 --> 00:04:42.770 align:middle line:84% Down here, we have what most of us focus on in one way 00:04:42.770 --> 00:04:46.332 align:middle line:84% or another, marine chemists, marine biologists, just ecology. 00:04:46.332 --> 00:04:48.290 align:middle line:84% Well, there's deep stuff too, but-- well, we'll 00:04:48.290 --> 00:04:51.730 align:middle line:84% talk about surface for now because ecology. 00:04:51.730 --> 00:04:54.240 align:middle line:84% And through a lot of these biological processes, 00:04:54.240 --> 00:04:57.340 align:middle line:84% we have formation or uptake of these climatically-relevant 00:04:57.340 --> 00:05:02.020 align:middle line:84% gases, so your carbon dioxide, your oxygen, sulfur gases, 00:05:02.020 --> 00:05:05.560 align:middle line:84% such as dimethyl sulfide, nitrous oxide. 00:05:05.560 --> 00:05:08.260 align:middle line:84% And eventually those are ventilated to the atmosphere 00:05:08.260 --> 00:05:10.340 align:middle line:84% through gas exchange processes, which I believe 00:05:10.340 --> 00:05:12.740 align:middle line:90% you talked about on Tuesday. 00:05:12.740 --> 00:05:14.320 align:middle line:84% Once they get up into the atmosphere, 00:05:14.320 --> 00:05:15.840 align:middle line:90% they can do a variety of things. 00:05:15.840 --> 00:05:21.080 align:middle line:84% They can affect the temperature through greenhouse-gas effects, 00:05:21.080 --> 00:05:22.280 align:middle line:90% which we'll talk about. 00:05:22.280 --> 00:05:24.380 align:middle line:84% They can affect ozone concentrations 00:05:24.380 --> 00:05:26.100 align:middle line:90% through a lot of chemistry-- 00:05:26.100 --> 00:05:27.940 align:middle line:90% I'm blocking your view there-- 00:05:27.940 --> 00:05:30.340 align:middle line:84% ozone concentrations through a lot of chemical reactions, 00:05:30.340 --> 00:05:31.700 align:middle line:90% which I'll touch on later. 00:05:31.700 --> 00:05:35.080 align:middle line:84% And they can also directly affect the radiation budget, 00:05:35.080 --> 00:05:36.520 align:middle line:90% which we'll also talk about. 00:05:36.520 --> 00:05:41.100 align:middle line:84% And then these leads lead to other secondary things happening 00:05:41.100 --> 00:05:43.780 align:middle line:84% in the atmosphere, like change in cloud microphysics, which I 00:05:43.780 --> 00:05:46.220 align:middle line:90% won't really talk about today. 00:05:46.220 --> 00:05:49.700 align:middle line:84% The temperatures can affect the chemical reaction rates. 00:05:49.700 --> 00:05:53.750 align:middle line:84% And so different pathways will happen in different proportions. 00:05:53.750 --> 00:05:56.750 align:middle line:84% It's also the oxidizing capacity of the atmosphere 00:05:56.750 --> 00:05:59.510 align:middle line:90% and the hydrological cycle. 00:05:59.510 --> 00:06:03.853 align:middle line:84% And so then what you have is you have all these reactions 00:06:03.853 --> 00:06:06.270 align:middle line:84% happening in the atmosphere and all these different things 00:06:06.270 --> 00:06:09.690 align:middle line:84% being formed and either forming with droplets and clouds. 00:06:09.690 --> 00:06:11.690 align:middle line:84% I'm going to talk about all the specifics later. 00:06:11.690 --> 00:06:13.190 align:middle line:84% And then there's a lot of deposition 00:06:13.190 --> 00:06:15.750 align:middle line:90% back onto the oceanic surface. 00:06:15.750 --> 00:06:18.130 align:middle line:84% So we have sulfur returning to the surface. 00:06:18.130 --> 00:06:20.630 align:middle line:84% We have nitrogen. We have iron, all being deposited 00:06:20.630 --> 00:06:22.430 align:middle line:90% in the oceanic surface. 00:06:22.430 --> 00:06:24.590 align:middle line:84% And those are going to feed back into the ecology 00:06:24.590 --> 00:06:26.630 align:middle line:90% through primary production. 00:06:26.630 --> 00:06:31.590 align:middle line:84% But there's also going to be a lot of physical processes 00:06:31.590 --> 00:06:32.890 align:middle line:90% to that effect. 00:06:32.890 --> 00:06:35.310 align:middle line:84% For example, if we warm the environment, 00:06:35.310 --> 00:06:37.150 align:middle line:90% we're going to warm the water. 00:06:37.150 --> 00:06:39.750 align:middle line:84% And if we warm that upper layer of water, 00:06:39.750 --> 00:06:41.870 align:middle line:84% that's going to change the mixing, which 00:06:41.870 --> 00:06:44.350 align:middle line:90% will affect nutrient delivery. 00:06:44.350 --> 00:06:47.110 align:middle line:84% And there's also a host of photochemical reactions 00:06:47.110 --> 00:06:47.915 align:middle line:90% that occur. 00:06:47.915 --> 00:06:50.040 align:middle line:84% And that's going to be a function of how much light 00:06:50.040 --> 00:06:52.400 align:middle line:90% reaches the oceanic surface. 00:06:52.400 --> 00:06:55.600 align:middle line:84% So the end point of this is that sunlight is a very powerful 00:06:55.600 --> 00:06:56.940 align:middle line:90% structuring agent. 00:06:56.940 --> 00:07:00.160 align:middle line:84% And this is the summary of what we're going 00:07:00.160 --> 00:07:03.600 align:middle line:90% to be talking about today. 00:07:03.600 --> 00:07:07.560 align:middle line:84% So I think you guys have already seen this. 00:07:07.560 --> 00:07:09.440 align:middle line:84% This is in general in parts per million 00:07:09.440 --> 00:07:13.320 align:middle line:84% by volume, the components of the atmosphere. 00:07:13.320 --> 00:07:16.200 align:middle line:84% And so pretty much the standard, what most people know 00:07:16.200 --> 00:07:20.560 align:middle line:84% is that the atmosphere is 78% nitrogen-- 00:07:20.560 --> 00:07:21.960 align:middle line:90% hello? 00:07:21.960 --> 00:07:28.120 align:middle line:84% is that-- 78% nitrogen and 21% oxygen. 00:07:28.120 --> 00:07:32.880 align:middle line:84% All the rest of these components are known as trace species, 00:07:32.880 --> 00:07:35.240 align:middle line:84% and they all contribute less than 1% 00:07:35.240 --> 00:07:37.680 align:middle line:84% of the total mass in the atmosphere. 00:07:37.680 --> 00:07:40.480 align:middle line:84% But they're pretty much the species 00:07:40.480 --> 00:07:43.020 align:middle line:84% that have the largest impact on the radiation budget 00:07:43.020 --> 00:07:46.080 align:middle line:84% and then the chemical input to the ocean. 00:07:46.080 --> 00:07:50.800 align:middle line:84% So water vapor is by far the most variable trace component, 00:07:50.800 --> 00:07:53.740 align:middle line:84% and that varies seasonally and regionally. 00:07:53.740 --> 00:07:57.360 align:middle line:84% And argon is probably the most abundant, but it's an inert gas, 00:07:57.360 --> 00:08:00.073 align:middle line:84% so I'm not really going to talk about it much today. 00:08:00.073 --> 00:08:02.740 align:middle line:84% Some of the other ones that I'm sure you've heard about in terms 00:08:02.740 --> 00:08:07.260 align:middle line:84% of greenhouse-gas warming, carbon dioxide, hydrogen, 00:08:07.260 --> 00:08:10.180 align:middle line:90% nitrous oxide, sulfur dioxide. 00:08:10.180 --> 00:08:15.340 align:middle line:84% And they vary very much in terms of their mixing ratios. 00:08:15.340 --> 00:08:19.880 align:middle line:84% As you can see, sulfur dioxide versus nitrogen, 00:08:19.880 --> 00:08:22.700 align:middle line:84% you've got about 10 order of magnitude difference. 00:08:22.700 --> 00:08:24.500 align:middle line:84% But in terms of climate effects, we're 00:08:24.500 --> 00:08:26.900 align:middle line:84% much more interested in sulfur than the nitrogen 00:08:26.900 --> 00:08:28.740 align:middle line:90% in the atmosphere. 00:08:28.740 --> 00:08:32.340 align:middle line:84% And also they vary a lot in terms of their lifetimes 00:08:32.340 --> 00:08:34.740 align:middle line:84% or just their residence times is a way 00:08:34.740 --> 00:08:37.179 align:middle line:84% to think about it in the environment. 00:08:37.179 --> 00:08:41.100 align:middle line:84% Nitrogen can go for can survive for 10 to the 7th to 10 00:08:41.100 --> 00:08:42.840 align:middle line:90% to the 9th years. 00:08:42.840 --> 00:08:44.340 align:middle line:84% So once it's up there, it's up there 00:08:44.340 --> 00:08:47.790 align:middle line:84% and in a chemically-inert form for a really long time. 00:08:47.790 --> 00:08:52.390 align:middle line:84% And then ozone, which I'll talk about in detail later, 00:08:52.390 --> 00:08:55.650 align:middle line:84% it only lasts for a couple days at the high latitudes. 00:08:55.650 --> 00:08:58.670 align:middle line:84% So understanding their lifetimes and their distributions 00:08:58.670 --> 00:09:00.230 align:middle line:84% can tell us a lot about the chemical 00:09:00.230 --> 00:09:02.690 align:middle line:84% processes that form them and where they come from. 00:09:02.690 --> 00:09:06.990 align:middle line:90% 00:09:06.990 --> 00:09:13.230 align:middle line:84% So one really special class of substances in the atmosphere 00:09:13.230 --> 00:09:15.690 align:middle line:90% is what's known as aerosols. 00:09:15.690 --> 00:09:21.070 align:middle line:90% 00:09:21.070 --> 00:09:24.070 align:middle line:90% Excuse me. 00:09:24.070 --> 00:09:28.850 align:middle line:84% These are the most important to us in this sort of environment 00:09:28.850 --> 00:09:32.430 align:middle line:84% because they have a direct effect on the radiation budget. 00:09:32.430 --> 00:09:34.750 align:middle line:84% And so really the way you define an aerosol is 00:09:34.750 --> 00:09:38.430 align:middle line:84% it's a suspension of particles in a gas. 00:09:38.430 --> 00:09:40.030 align:middle line:84% And if it's liquid particles, it's 00:09:40.030 --> 00:09:42.750 align:middle line:84% generally things we think of like clouds 00:09:42.750 --> 00:09:45.680 align:middle line:90% or mist, that type of mixture. 00:09:45.680 --> 00:09:48.540 align:middle line:84% And if it's a suspension of solid particles, 00:09:48.540 --> 00:09:52.400 align:middle line:84% we generally think of it as dust or smoke or soot, 00:09:52.400 --> 00:09:54.200 align:middle line:90% that type of particles. 00:09:54.200 --> 00:09:58.520 align:middle line:84% And we're interested in aerosols for two basic reasons, 00:09:58.520 --> 00:10:03.880 align:middle line:84% for two basic radiative reasons, the direct and indirect effect 00:10:03.880 --> 00:10:07.800 align:middle line:90% on the incoming solar flux. 00:10:07.800 --> 00:10:09.382 align:middle line:90% So the way it works is-- 00:10:09.382 --> 00:10:11.340 align:middle line:84% I'm just going to define these really quickly-- 00:10:11.340 --> 00:10:13.800 align:middle line:84% is that the direct effect, it relates to changes 00:10:13.800 --> 00:10:17.840 align:middle line:84% in the net radiative flux, so the total amount of photons 00:10:17.840 --> 00:10:21.440 align:middle line:84% coming in from the sun in the atmosphere. 00:10:21.440 --> 00:10:24.320 align:middle line:84% These aerosols modulate the absorbing and scattering 00:10:24.320 --> 00:10:26.800 align:middle line:90% properties of the atmosphere. 00:10:26.800 --> 00:10:29.980 align:middle line:84% So chemically, depending on what form they're in, 00:10:29.980 --> 00:10:32.520 align:middle line:84% they'll absorb at different wavebands. 00:10:32.520 --> 00:10:34.480 align:middle line:84% And depending on their size, they're 00:10:34.480 --> 00:10:37.480 align:middle line:84% going to scatter in different directions. 00:10:37.480 --> 00:10:38.917 align:middle line:84% And so eventually what that means 00:10:38.917 --> 00:10:41.000 align:middle line:84% is that you're changing the aerosol concentrations 00:10:41.000 --> 00:10:43.650 align:middle line:90% in the optical properties. 00:10:43.650 --> 00:10:45.570 align:middle line:84% Something we won't talk about as much today 00:10:45.570 --> 00:10:48.410 align:middle line:84% is what's known as the indirect effect. 00:10:48.410 --> 00:10:51.170 align:middle line:84% And what this has to do is that aerosols 00:10:51.170 --> 00:10:55.490 align:middle line:84% themselves can change cloud properties because it's 00:10:55.490 --> 00:10:58.710 align:middle line:90% very hard for a cloud to form. 00:10:58.710 --> 00:11:01.810 align:middle line:84% You have to have something for water to condense on. 00:11:01.810 --> 00:11:03.850 align:middle line:84% There are occasions where water molecules 00:11:03.850 --> 00:11:06.470 align:middle line:84% will condense together, which is how you start. 00:11:06.470 --> 00:11:09.290 align:middle line:84% But it's much easier for water to condense onto something 00:11:09.290 --> 00:11:11.090 align:middle line:90% in the atmosphere. 00:11:11.090 --> 00:11:14.215 align:middle line:84% And so aerosols form a perfect surface for this reaction. 00:11:14.215 --> 00:11:16.090 align:middle line:84% So they're a little particle floating around. 00:11:16.090 --> 00:11:17.970 align:middle line:90% The water can condense on them. 00:11:17.970 --> 00:11:19.930 align:middle line:84% And so you can change the number of clouds 00:11:19.930 --> 00:11:21.470 align:middle line:90% and the number of droplets. 00:11:21.470 --> 00:11:24.590 align:middle line:84% And that's going to affect your radiation budget. 00:11:24.590 --> 00:11:26.973 align:middle line:90% 00:11:26.973 --> 00:11:27.890 align:middle line:90% AUDIENCE: Can I just-- 00:11:27.890 --> 00:11:29.015 align:middle line:90% DIEDRE TOOLE: Yeah, please. 00:11:29.015 --> 00:11:31.457 align:middle line:84% AUDIENCE: Is it possible to get the picture-in-picture out 00:11:31.457 --> 00:11:32.290 align:middle line:90% of the screen there? 00:11:32.290 --> 00:11:33.385 align:middle line:90% AUDIENCE: Oh, yeah. 00:11:33.385 --> 00:11:34.010 align:middle line:90% AUDIENCE: Yeah. 00:11:34.010 --> 00:11:37.718 align:middle line:90% 00:11:37.718 --> 00:11:39.010 align:middle line:90% DIEDRE TOOLE: What's happening? 00:11:39.010 --> 00:11:41.898 align:middle line:84% AUDIENCE: With the-- this is then-- if you're blocking it, 00:11:41.898 --> 00:11:42.940 align:middle line:90% we can read it off of it. 00:11:42.940 --> 00:11:43.840 align:middle line:90% DIEDRE TOOLE: Oh, I'm sorry. 00:11:43.840 --> 00:11:44.280 align:middle line:90% AUDIENCE: [INAUDIBLE] 00:11:44.280 --> 00:11:45.780 align:middle line:84% DIEDRE TOOLE: I need to be like-- 00:11:45.780 --> 00:11:47.147 align:middle line:90% I wish I had a remote for the-- 00:11:47.147 --> 00:11:47.980 align:middle line:90% AUDIENCE: It's fine. 00:11:47.980 --> 00:11:50.660 align:middle line:90% DIEDRE TOOLE: It is how it is. 00:11:50.660 --> 00:11:51.500 align:middle line:90% OK. 00:11:51.500 --> 00:11:53.140 align:middle line:90% No problem. 00:11:53.140 --> 00:11:56.500 align:middle line:84% So just to understand, this is more just 00:11:56.500 --> 00:11:58.500 align:middle line:84% to tell you that there's a lot of different ways 00:11:58.500 --> 00:12:01.260 align:middle line:84% in the environment that we can form aerosols. 00:12:01.260 --> 00:12:03.400 align:middle line:84% The details of this aren't as important. 00:12:03.400 --> 00:12:07.340 align:middle line:84% What's really important is that you understand 00:12:07.340 --> 00:12:10.700 align:middle line:84% that you can have this homogeneous, homomolecular 00:12:10.700 --> 00:12:12.460 align:middle line:90% reaction where-- 00:12:12.460 --> 00:12:14.060 align:middle line:90% just losing pieces of this-- 00:12:14.060 --> 00:12:19.540 align:middle line:84% where single gas components, they can condense together 00:12:19.540 --> 00:12:21.820 align:middle line:90% to form a suspended particle. 00:12:21.820 --> 00:12:23.620 align:middle line:84% And this is basically water molecules 00:12:23.620 --> 00:12:27.280 align:middle line:84% coming together and condensing at the right temperature. 00:12:27.280 --> 00:12:29.000 align:middle line:84% And they can start making the clouds. 00:12:29.000 --> 00:12:31.140 align:middle line:90% But that's fairly rare. 00:12:31.140 --> 00:12:35.800 align:middle line:84% You also have this homogeneous, heteromolecular-type reactions. 00:12:35.800 --> 00:12:38.260 align:middle line:84% And that's the reaction of two or more gases 00:12:38.260 --> 00:12:40.640 align:middle line:90% to form a new particle. 00:12:40.640 --> 00:12:42.620 align:middle line:84% And this is just an example of ammonia 00:12:42.620 --> 00:12:46.440 align:middle line:84% plus nitric acid gives you ammonium nitrate. 00:12:46.440 --> 00:12:48.960 align:middle line:84% And so once you have these solids, 00:12:48.960 --> 00:12:51.160 align:middle line:90% it's an exponential process. 00:12:51.160 --> 00:12:55.640 align:middle line:84% You have a new surface for something to condense on. 00:12:55.640 --> 00:12:58.860 align:middle line:84% And that's what this third reaction type is. 00:12:58.860 --> 00:13:01.080 align:middle line:84% It's a heterogeneous, heteromolecular. 00:13:01.080 --> 00:13:03.133 align:middle line:84% This is also known as aerosol scavenging. 00:13:03.133 --> 00:13:04.800 align:middle line:84% And this is one of the most common types 00:13:04.800 --> 00:13:07.160 align:middle line:90% of reactions in the atmosphere. 00:13:07.160 --> 00:13:10.940 align:middle line:84% And that's where gases react with a pre-existing particle. 00:13:10.940 --> 00:13:15.700 align:middle line:90% 00:13:15.700 --> 00:13:17.200 align:middle line:84% And so in this case, what we have is 00:13:17.200 --> 00:13:20.440 align:middle line:84% we have sodium chloride, which is basically sea salt, something 00:13:20.440 --> 00:13:21.620 align:middle line:90% we'll talk about later. 00:13:21.620 --> 00:13:24.480 align:middle line:84% And that provides this really reactive surface, 00:13:24.480 --> 00:13:26.180 align:middle line:90% where gases can condense. 00:13:26.180 --> 00:13:28.960 align:middle line:84% And in this case, it's nitric acid. 00:13:28.960 --> 00:13:32.240 align:middle line:84% And you end up with HCl and sodium nitrate. 00:13:32.240 --> 00:13:34.520 align:middle line:84% And what these solid particles do 00:13:34.520 --> 00:13:38.410 align:middle line:84% is they change the partitioning of some of the key species 00:13:38.410 --> 00:13:40.330 align:middle line:84% that we need to understand, to understand some 00:13:40.330 --> 00:13:42.650 align:middle line:90% of the atmospheric chemistry. 00:13:42.650 --> 00:13:44.510 align:middle line:84% And then the fourth type of reaction, 00:13:44.510 --> 00:13:46.210 align:middle line:84% fourth type of aerosol reaction you 00:13:46.210 --> 00:13:51.330 align:middle line:84% can have is chemical reaction within the aerosol itself. 00:13:51.330 --> 00:13:54.650 align:middle line:84% And this is really important in terms 00:13:54.650 --> 00:13:58.970 align:middle line:84% of turning sulfur dioxide into sulfur ions and some 00:13:58.970 --> 00:14:00.470 align:middle line:90% of the nitric-acid reactions. 00:14:00.470 --> 00:14:02.095 align:middle line:84% Basically, this is really important for 00:14:02.095 --> 00:14:05.730 align:middle line:90% the acid rain-type reactions. 00:14:05.730 --> 00:14:09.550 align:middle line:84% And that changes the composition of the particles themselves. 00:14:09.550 --> 00:14:13.290 align:middle line:90% 00:14:13.290 --> 00:14:16.690 align:middle line:84% So just to say in a nutshell, really 00:14:16.690 --> 00:14:19.090 align:middle line:84% why we care about the aerosols in the environment 00:14:19.090 --> 00:14:22.970 align:middle line:84% is because of their absorption and scattering abilities 00:14:22.970 --> 00:14:24.630 align:middle line:84% because ultimately, as oceanographers, 00:14:24.630 --> 00:14:26.970 align:middle line:84% what we're concerned about is the amount of light 00:14:26.970 --> 00:14:29.170 align:middle line:84% that hits the surface of the ocean. 00:14:29.170 --> 00:14:32.090 align:middle line:84% And it's all the absorbers and all the scatterers 00:14:32.090 --> 00:14:35.770 align:middle line:84% in the environment that is going to affect the amount of light. 00:14:35.770 --> 00:14:37.700 align:middle line:84% And so different gases and aerosols 00:14:37.700 --> 00:14:40.300 align:middle line:84% are going to absorb at different wavelengths, 00:14:40.300 --> 00:14:43.500 align:middle line:84% and that's a function of what chemical they are. 00:14:43.500 --> 00:14:45.760 align:middle line:84% For example-- something we'll talk about later. 00:14:45.760 --> 00:14:48.900 align:middle line:84% It's really important-- is the direct absorption of UV 00:14:48.900 --> 00:14:50.420 align:middle line:90% by ozone. 00:14:50.420 --> 00:14:52.880 align:middle line:84% And so that can affect the heat balance in the atmosphere. 00:14:52.880 --> 00:14:54.780 align:middle line:84% But it also affects the penetration 00:14:54.780 --> 00:14:59.740 align:middle line:84% of wavelengths less than 290 nanometers. 00:14:59.740 --> 00:15:01.923 align:middle line:90% Also, we have scattering. 00:15:01.923 --> 00:15:03.340 align:middle line:84% And scattering is really important 00:15:03.340 --> 00:15:05.500 align:middle line:84% to understand in terms of the light reaching 00:15:05.500 --> 00:15:07.620 align:middle line:84% the surface of the ocean because if we 00:15:07.620 --> 00:15:10.600 align:middle line:84% didn't have any scattering in the environment, 00:15:10.600 --> 00:15:14.480 align:middle line:84% the sun would just be one beam coming straight down. 00:15:14.480 --> 00:15:16.227 align:middle line:84% It would be very much a direct beam. 00:15:16.227 --> 00:15:17.560 align:middle line:90% But we know that's not the case. 00:15:17.560 --> 00:15:18.928 align:middle line:90% There's a lot of diffuse light. 00:15:18.928 --> 00:15:20.720 align:middle line:84% If you look outside, I mean, you don't just 00:15:20.720 --> 00:15:21.985 align:middle line:90% see a single collimated beam. 00:15:21.985 --> 00:15:23.860 align:middle line:84% You see there's a lot of diffuse light coming 00:15:23.860 --> 00:15:26.620 align:middle line:84% from a lot of different areas of the sky. 00:15:26.620 --> 00:15:30.260 align:middle line:84% And that is pretty much from scattering in the atmosphere. 00:15:30.260 --> 00:15:32.365 align:middle line:84% And there's two types of scattering. 00:15:32.365 --> 00:15:34.240 align:middle line:84% I won't really go into these very much today, 00:15:34.240 --> 00:15:36.973 align:middle line:84% but there's what's known as Rayleigh scattering. 00:15:36.973 --> 00:15:39.390 align:middle line:84% And that's when particles are generally the really, really 00:15:39.390 --> 00:15:40.790 align:middle line:90% small particles. 00:15:40.790 --> 00:15:44.030 align:middle line:84% And that's gases, gases that have just 00:15:44.030 --> 00:15:46.550 align:middle line:84% started their homogeneous reactions and are really small 00:15:46.550 --> 00:15:47.750 align:middle line:90% still. 00:15:47.750 --> 00:15:49.510 align:middle line:84% The much more common type of scattering 00:15:49.510 --> 00:15:51.750 align:middle line:84% is what we can call Mie scattering. 00:15:51.750 --> 00:15:54.830 align:middle line:84% And that's when particles are either equal to or much greater 00:15:54.830 --> 00:15:57.170 align:middle line:84% than the wavelength of light, for example, 00:15:57.170 --> 00:16:00.150 align:middle line:84% the aerosols and cloud droplets I've been talking about. 00:16:00.150 --> 00:16:03.850 align:middle line:84% And those are much more forward scattering, 00:16:03.850 --> 00:16:07.550 align:middle line:90% but they also diffuse the light. 00:16:07.550 --> 00:16:09.590 align:middle line:84% And so for example, even the smallest aerosols 00:16:09.590 --> 00:16:13.390 align:middle line:84% that we were concerned about, the cloud-condensation nuclei, 00:16:13.390 --> 00:16:16.320 align:middle line:84% which as I mentioned were when the water droplets condense 00:16:16.320 --> 00:16:18.070 align:middle line:84% together and you have that little particle 00:16:18.070 --> 00:16:20.550 align:middle line:84% to start forming clouds on, those 00:16:20.550 --> 00:16:23.230 align:middle line:84% are already on the order of 0.1 micron, which 00:16:23.230 --> 00:16:27.030 align:middle line:84% is much bigger than most of the solar radiation that's 00:16:27.030 --> 00:16:28.850 align:middle line:84% going to be coming directly from the sun. 00:16:28.850 --> 00:16:33.440 align:middle line:90% 00:16:33.440 --> 00:16:34.280 align:middle line:90% OK. 00:16:34.280 --> 00:16:41.353 align:middle line:84% So in terms of the Earth energies figure before-- yeah. 00:16:41.353 --> 00:16:42.520 align:middle line:90% AUDIENCE: It's in the notes? 00:16:42.520 --> 00:16:43.560 align:middle line:90% DIEDRE TOOLE: Yeah. 00:16:43.560 --> 00:16:45.880 align:middle line:90% I think this is the notes. 00:16:45.880 --> 00:16:47.820 align:middle line:84% There's a lot of partitioning, I mean, 00:16:47.820 --> 00:16:52.240 align:middle line:84% in terms of you have your solar constant 00:16:52.240 --> 00:16:55.680 align:middle line:84% at the top of the atmosphere, and then you can partition that 00:16:55.680 --> 00:16:59.280 align:middle line:84% into an average solar flux based on some geometrical concerns 00:16:59.280 --> 00:17:01.960 align:middle line:84% and the surface cross-section of the Earth 00:17:01.960 --> 00:17:04.680 align:middle line:84% and the surface, the area of the Earth. 00:17:04.680 --> 00:17:07.760 align:middle line:84% And you come in with this average incoming solar radiation 00:17:07.760 --> 00:17:12.319 align:middle line:84% flux of 342 watts per meter squared. 00:17:12.319 --> 00:17:16.240 align:middle line:84% And this is coming from the sun, straight from the sun. 00:17:16.240 --> 00:17:18.000 align:middle line:84% So obviously it doesn't penetrate 00:17:18.000 --> 00:17:22.359 align:middle line:84% straight to the surface of the Earth because the aerosols 00:17:22.359 --> 00:17:23.480 align:middle line:90% that we just talked about. 00:17:23.480 --> 00:17:29.080 align:middle line:84% You have a fair amount of 20% maybe 00:17:29.080 --> 00:17:32.860 align:middle line:84% that's reflected by the clouds and aerosols in the atmosphere. 00:17:32.860 --> 00:17:34.700 align:middle line:84% So it's important for us to understand 00:17:34.700 --> 00:17:36.843 align:middle line:84% the amount of aerosols and the amount of clouds 00:17:36.843 --> 00:17:38.260 align:middle line:84% because that's going to affect how 00:17:38.260 --> 00:17:42.180 align:middle line:84% much solar radiation directly reaches and can reach the ocean 00:17:42.180 --> 00:17:43.580 align:middle line:90% surface. 00:17:43.580 --> 00:17:48.060 align:middle line:84% You also have some direct absorption by the atmosphere, 00:17:48.060 --> 00:17:51.780 align:middle line:84% and that's primarily in the-- well, I'll show you a second. 00:17:51.780 --> 00:17:54.980 align:middle line:84% That depends on the chemicals that are in the environment. 00:17:54.980 --> 00:17:56.860 align:middle line:84% But for a large part, a large chunk of it 00:17:56.860 --> 00:17:58.980 align:middle line:84% makes it all the way through to either be 00:17:58.980 --> 00:18:02.460 align:middle line:84% absorbed by the surface or reflected 00:18:02.460 --> 00:18:04.620 align:middle line:90% by the surface radiation. 00:18:04.620 --> 00:18:07.140 align:middle line:84% And this amount of reflection is very-- 00:18:07.140 --> 00:18:09.540 align:middle line:90% it's very spatially variable. 00:18:09.540 --> 00:18:12.913 align:middle line:84% And if you think about it, if sunlight hits an ice cap, 00:18:12.913 --> 00:18:14.080 align:middle line:90% there's a lot of reflection. 00:18:14.080 --> 00:18:14.820 align:middle line:90% It's white. 00:18:14.820 --> 00:18:17.900 align:middle line:84% Whereas if the sunlight hits the ocean, 00:18:17.900 --> 00:18:19.200 align:middle line:90% it's a really dark target. 00:18:19.200 --> 00:18:21.222 align:middle line:84% So you're going to get less than 5% reflection. 00:18:21.222 --> 00:18:22.680 align:middle line:84% A lot of it's going to be absorbed. 00:18:22.680 --> 00:18:25.740 align:middle line:84% So these numbers are dynamic depending 00:18:25.740 --> 00:18:32.338 align:middle line:84% on what's in the atmosphere, the size of ice caps, land cover, 00:18:32.338 --> 00:18:33.130 align:middle line:90% that sort of thing. 00:18:33.130 --> 00:18:38.312 align:middle line:84% So these are just a current estimate of these numbers. 00:18:38.312 --> 00:18:40.270 align:middle line:84% What we haven't talked about yet, which is also 00:18:40.270 --> 00:18:42.895 align:middle line:84% really important in the Earth's energy budget and the radiation 00:18:42.895 --> 00:18:46.620 align:middle line:84% budget, is the concept of greenhouse gases over here. 00:18:46.620 --> 00:18:47.870 align:middle line:90% AUDIENCE: We did go over that. 00:18:47.870 --> 00:18:49.070 align:middle line:84% DIEDRE TOOLE: Oh, did you go over it? 00:18:49.070 --> 00:18:49.695 align:middle line:90% AUDIENCE: Yeah. 00:18:49.695 --> 00:18:50.430 align:middle line:90% DIEDRE TOOLE: OK. 00:18:50.430 --> 00:18:50.890 align:middle line:90% OK. 00:18:50.890 --> 00:18:52.070 align:middle line:84% Well, we're going to skip through some 00:18:52.070 --> 00:18:53.270 align:middle line:90% of this really quick. 00:18:53.270 --> 00:18:54.412 align:middle line:90% OK. 00:18:54.412 --> 00:18:56.370 align:middle line:84% You guys have already had the Stefan-Boltzmann. 00:18:56.370 --> 00:18:56.650 align:middle line:90% OK. 00:18:56.650 --> 00:18:58.650 align:middle line:84% Well, we'll just skip through that really quick. 00:18:58.650 --> 00:19:01.890 align:middle line:84% So in terms of what I'm going to be talking about today-- 00:19:01.890 --> 00:19:06.370 align:middle line:84% you already know the distribution, the wavelengths, 00:19:06.370 --> 00:19:09.270 align:middle line:84% the radiation is a function of their temperature, 00:19:09.270 --> 00:19:12.590 align:middle line:90% based on the blackbody emitter. 00:19:12.590 --> 00:19:15.430 align:middle line:84% But in terms of what we're interested in terms of gases 00:19:15.430 --> 00:19:20.190 align:middle line:90% and aerosols in the atmosphere. 00:19:20.190 --> 00:19:24.670 align:middle line:84% They each have specific infrared absorption bands. 00:19:24.670 --> 00:19:28.760 align:middle line:84% And they add up within the atmosphere. 00:19:28.760 --> 00:19:32.040 align:middle line:84% They individually have absorption bands, 00:19:32.040 --> 00:19:33.800 align:middle line:84% and they add up within the atmosphere 00:19:33.800 --> 00:19:38.680 align:middle line:84% to form the total absorption spectra of the atmosphere. 00:19:38.680 --> 00:19:42.080 align:middle line:90% And so that means-- 00:19:42.080 --> 00:19:44.560 align:middle line:84% AUDIENCE: Can you tell us about the axis on the figures? 00:19:44.560 --> 00:19:45.520 align:middle line:90% DIEDRE TOOLE: Oh, yeah. 00:19:45.520 --> 00:19:48.360 align:middle line:90% This is wavelength here. 00:19:48.360 --> 00:19:51.400 align:middle line:90% And it starts down-- 00:19:51.400 --> 00:19:56.240 align:middle line:84% in terms of what we're familiar with, this is the solar. 00:19:56.240 --> 00:19:58.340 align:middle line:84% This is the visible region in here. 00:19:58.340 --> 00:20:02.800 align:middle line:90% It's about 400 to 700 in here. 00:20:02.800 --> 00:20:08.720 align:middle line:84% And then this is the infrared region through here. 00:20:08.720 --> 00:20:12.120 align:middle line:84% And so on these scales, ignoring the first one, 00:20:12.120 --> 00:20:14.260 align:middle line:90% it's absorptivity. 00:20:14.260 --> 00:20:16.120 align:middle line:90% So it's percentage. 00:20:16.120 --> 00:20:16.620 align:middle line:90% Is it? 00:20:16.620 --> 00:20:18.460 align:middle line:90% Yeah, in terms of percentage. 00:20:18.460 --> 00:20:22.760 align:middle line:84% So what you can see, again, is that depending 00:20:22.760 --> 00:20:26.200 align:middle line:84% on which gases actually are in the atmosphere, 00:20:26.200 --> 00:20:28.930 align:middle line:84% it's going to depend on which wavelengths get absorbed 00:20:28.930 --> 00:20:29.930 align:middle line:90% and where. 00:20:29.930 --> 00:20:33.810 align:middle line:84% And for the most part, it's generally clear 00:20:33.810 --> 00:20:35.790 align:middle line:84% in terms of absorption by the atmosphere 00:20:35.790 --> 00:20:39.490 align:middle line:84% here, the wavelengths, the peak wavelengths of the sun. 00:20:39.490 --> 00:20:45.510 align:middle line:84% But you notice the greenhouse gases here, methane, water, 00:20:45.510 --> 00:20:48.250 align:middle line:84% oxygen, ozone, carbon dioxide, and water, 00:20:48.250 --> 00:20:51.153 align:middle line:84% they have huge absorption peaks in the infrared range. 00:20:51.153 --> 00:20:53.070 align:middle line:84% So they're going to trap a lot of those gases. 00:20:53.070 --> 00:20:56.490 align:middle line:90% We're going to have warming. 00:20:56.490 --> 00:20:57.850 align:middle line:90% Can I go through this quickly? 00:20:57.850 --> 00:21:06.050 align:middle line:84% One thing that I just wanted to point out is that in terms of-- 00:21:06.050 --> 00:21:10.410 align:middle line:84% if you individually look at the components of each gas 00:21:10.410 --> 00:21:15.170 align:middle line:84% currently and add them up, it doesn't come out 00:21:15.170 --> 00:21:16.770 align:middle line:90% exactly the same. 00:21:16.770 --> 00:21:19.610 align:middle line:84% For example, how do I explain this? 00:21:19.610 --> 00:21:21.070 align:middle line:90% Carbon dioxide, for example. 00:21:21.070 --> 00:21:26.700 align:middle line:84% Right now, they estimate that it absorbs about 12% 00:21:26.700 --> 00:21:29.700 align:middle line:90% of the radiation coming in. 00:21:29.700 --> 00:21:32.380 align:middle line:84% But that's because there are other constituents 00:21:32.380 --> 00:21:35.300 align:middle line:84% in the atmosphere that are able to absorb 00:21:35.300 --> 00:21:36.780 align:middle line:90% that infrared radiation. 00:21:36.780 --> 00:21:39.980 align:middle line:84% If you were to take everything out, 00:21:39.980 --> 00:21:43.940 align:middle line:84% besides carbon dioxide, that absorbs that infrared radiation, 00:21:43.940 --> 00:21:45.460 align:middle line:84% the carbon dioxide could actually 00:21:45.460 --> 00:21:49.608 align:middle line:84% end up absorbing a lot more, factor of three or four more. 00:21:49.608 --> 00:21:51.900 align:middle line:84% So it's important to think about these changes in terms 00:21:51.900 --> 00:21:53.740 align:middle line:84% of climate-change scenarios, where 00:21:53.740 --> 00:21:56.620 align:middle line:84% if the different levels of the different gases change, 00:21:56.620 --> 00:22:00.100 align:middle line:84% that it might actually change our net effect of absorbing 00:22:00.100 --> 00:22:01.040 align:middle line:90% of the infrared. 00:22:01.040 --> 00:22:13.660 align:middle line:90% 00:22:13.660 --> 00:22:17.040 align:middle line:84% I'm not sure how familiar you guys are with this, 00:22:17.040 --> 00:22:19.780 align:middle line:84% but I wanted to show you an example of what 00:22:19.780 --> 00:22:22.820 align:middle line:84% the solar spectrum looks like when it actually reaches 00:22:22.820 --> 00:22:25.320 align:middle line:84% the surface of the ocean because we 00:22:25.320 --> 00:22:30.680 align:middle line:84% have that idealized black-body curve coming from the sun. 00:22:30.680 --> 00:22:33.920 align:middle line:84% But clearly, as we have absorbing and scattering 00:22:33.920 --> 00:22:36.000 align:middle line:84% the atmosphere, the spectral composition 00:22:36.000 --> 00:22:39.112 align:middle line:84% is going to change as it reaches the ocean surface. 00:22:39.112 --> 00:22:40.820 align:middle line:84% And so what we have in this figure again, 00:22:40.820 --> 00:22:44.520 align:middle line:84% is we have wavelength on the x-axis and then 00:22:44.520 --> 00:22:46.760 align:middle line:84% the spectral irradiance in terms of watts per meter 00:22:46.760 --> 00:22:49.880 align:middle line:90% squared per square micron. 00:22:49.880 --> 00:22:54.640 align:middle line:84% And the blue line, this is the solar irradiance 00:22:54.640 --> 00:22:56.327 align:middle line:90% outside the atmosphere. 00:22:56.327 --> 00:22:58.160 align:middle line:84% So that's before there's been any processing 00:22:58.160 --> 00:23:00.080 align:middle line:90% by the gases or the aerosols. 00:23:00.080 --> 00:23:03.360 align:middle line:84% This is just what reaches the planet. 00:23:03.360 --> 00:23:08.080 align:middle line:84% And then the yellow line is the direct solar irradiance 00:23:08.080 --> 00:23:09.732 align:middle line:90% at sea level. 00:23:09.732 --> 00:23:11.940 align:middle line:84% So a couple of things are really important to notice. 00:23:11.940 --> 00:23:14.000 align:middle line:90% You can see these big dips. 00:23:14.000 --> 00:23:15.800 align:middle line:84% And those are from the absorption bands 00:23:15.800 --> 00:23:18.320 align:middle line:90% of the gases in the atmosphere. 00:23:18.320 --> 00:23:21.240 align:middle line:84% There's also a significant reduction in magnitude 00:23:21.240 --> 00:23:25.970 align:middle line:84% because a lot of that energy has been absorbed or scattered. 00:23:25.970 --> 00:23:28.473 align:middle line:84% And also another thing really interesting to notice, 00:23:28.473 --> 00:23:29.890 align:middle line:84% that we'll talk about in a second, 00:23:29.890 --> 00:23:35.490 align:middle line:84% is that these lower wavelengths are gone. 00:23:35.490 --> 00:23:38.090 align:middle line:84% The ozone is a really important exception 00:23:38.090 --> 00:23:40.130 align:middle line:84% in terms of its abilities, and it basically 00:23:40.130 --> 00:23:45.410 align:middle line:84% makes life as we know it able to happen because the sun is 00:23:45.410 --> 00:23:49.610 align:middle line:84% blasting us with these really highly-energetic short photons 00:23:49.610 --> 00:23:51.930 align:middle line:90% in this UVC range. 00:23:51.930 --> 00:23:55.530 align:middle line:84% I mean, they have photons anywhere shorter than 280 00:23:55.530 --> 00:23:56.230 align:middle line:90% nanometers. 00:23:56.230 --> 00:23:59.910 align:middle line:84% So if one of those photons were to make it to Earth, 00:23:59.910 --> 00:24:02.470 align:middle line:84% it's extremely destructive in terms of life. 00:24:02.470 --> 00:24:04.030 align:middle line:90% It damages nucleic acid. 00:24:04.030 --> 00:24:04.910 align:middle line:90% It damages proteins. 00:24:04.910 --> 00:24:08.050 align:middle line:90% You really can't have that. 00:24:08.050 --> 00:24:11.640 align:middle line:84% And ozone effectively blocks all of that. 00:24:11.640 --> 00:24:13.890 align:middle line:84% And you can see that in the difference between the two 00:24:13.890 --> 00:24:16.730 align:middle line:90% spectra there. 00:24:16.730 --> 00:24:20.980 align:middle line:84% So just to preface our talk to make sure-- 00:24:20.980 --> 00:24:22.700 align:middle line:84% there's a lot of terms people use 00:24:22.700 --> 00:24:26.580 align:middle line:84% when they talk about the different wavelengths of light. 00:24:26.580 --> 00:24:28.680 align:middle line:84% I mean, there's a little bit of play in these. 00:24:28.680 --> 00:24:32.340 align:middle line:84% But for the most part, UVCs are the really short, really 00:24:32.340 --> 00:24:35.820 align:middle line:90% energetic UV wavelengths. 00:24:35.820 --> 00:24:41.340 align:middle line:84% UVB wavelengths are generally in the 280 to 320-nanometer range. 00:24:41.340 --> 00:24:43.860 align:middle line:84% And those are often-- they inhibit a lot 00:24:43.860 --> 00:24:49.660 align:middle line:84% biological processes, bacterial production, primary production. 00:24:49.660 --> 00:24:51.420 align:middle line:84% But they're also involved in a lot 00:24:51.420 --> 00:24:55.660 align:middle line:84% of photolysis and photochemical-type reactions. 00:24:55.660 --> 00:24:59.000 align:middle line:84% UVA is a much longer UV wavelength. 00:24:59.000 --> 00:25:02.660 align:middle line:84% That's the 320 to 400-nanometer range. 00:25:02.660 --> 00:25:04.060 align:middle line:84% And those actually, in some cases 00:25:04.060 --> 00:25:08.100 align:middle line:84% can be good for some of the ecology going on. 00:25:08.100 --> 00:25:11.180 align:middle line:84% You can have a lot of repair processes that happen. 00:25:11.180 --> 00:25:14.300 align:middle line:84% If you're bacteria or phytoplankton in the upper water 00:25:14.300 --> 00:25:17.340 align:middle line:84% column and you're getting hit with UVA and not UVB, 00:25:17.340 --> 00:25:19.310 align:middle line:84% you can do a lot of your cellular functions 00:25:19.310 --> 00:25:22.030 align:middle line:90% that allow for repair. 00:25:22.030 --> 00:25:24.390 align:middle line:84% The visible wavelengths are generally 00:25:24.390 --> 00:25:27.870 align:middle line:84% considered 400 to 700 nanometers. 00:25:27.870 --> 00:25:29.950 align:middle line:84% And it's not a coincidence that that's 00:25:29.950 --> 00:25:35.230 align:middle line:84% the maximum of the solar output of the blackbody curve 00:25:35.230 --> 00:25:38.310 align:middle line:90% from the sun. 00:25:38.310 --> 00:25:42.430 align:middle line:84% And then infrared wavelengths go from about 700 nanometers 00:25:42.430 --> 00:25:47.750 align:middle line:84% up to 1 millimeter, where they start running into radio waves. 00:25:47.750 --> 00:25:55.470 align:middle line:84% But just to show you an example, this partitioning of light 00:25:55.470 --> 00:25:57.670 align:middle line:90% that hits the surface. 00:25:57.670 --> 00:25:59.530 align:middle line:90% It's a very dynamic thing. 00:25:59.530 --> 00:26:02.350 align:middle line:84% It's dependent on what's in the atmosphere. 00:26:02.350 --> 00:26:05.150 align:middle line:84% And as the concentrations of the chemicals and gases 00:26:05.150 --> 00:26:07.110 align:middle line:84% in the atmosphere change, the amount 00:26:07.110 --> 00:26:10.430 align:middle line:84% of light that hits the surface is going to change, too. 00:26:10.430 --> 00:26:13.710 align:middle line:84% And so this is just an example we took at Palmer Station 00:26:13.710 --> 00:26:17.880 align:middle line:84% in the year 2000, and this is also solar irradiance. 00:26:17.880 --> 00:26:23.120 align:middle line:84% But you can see that the red line corresponds to high ozone. 00:26:23.120 --> 00:26:26.260 align:middle line:84% And just so you guys know, this only goes from 290 to 350. 00:26:26.260 --> 00:26:28.080 align:middle line:84% So we're only halfway into the UVA. 00:26:28.080 --> 00:26:30.647 align:middle line:84% We're not all the way out to the visible or the IR. 00:26:30.647 --> 00:26:32.480 align:middle line:84% But you can see that there's this difference 00:26:32.480 --> 00:26:35.280 align:middle line:84% between these two spectra, based on high ozone 00:26:35.280 --> 00:26:37.840 align:middle line:84% concentrations in the red and low ozone 00:26:37.840 --> 00:26:40.360 align:middle line:90% concentrations in the blue. 00:26:40.360 --> 00:26:41.160 align:middle line:90% So what-- 00:26:41.160 --> 00:26:43.440 align:middle line:90% AUDIENCE: Stratospheric ozone? 00:26:43.440 --> 00:26:45.538 align:middle line:84% DIEDRE TOOLE: This is column-integrated ozone. 00:26:45.538 --> 00:26:46.080 align:middle line:90% AUDIENCE: OK. 00:26:46.080 --> 00:26:48.122 align:middle line:84% DIEDRE TOOLE: But yeah, generally down there it's 00:26:48.122 --> 00:26:51.200 align:middle line:84% stratospheric ozone what we're losing. 00:26:51.200 --> 00:26:56.680 align:middle line:84% And so effects on these aerosols up in the higher levels 00:26:56.680 --> 00:27:00.320 align:middle line:84% of the stratosphere can have direct effects on the biology 00:27:00.320 --> 00:27:02.560 align:middle line:84% in the upper layers of Antarctica, 00:27:02.560 --> 00:27:05.842 align:middle line:84% based on the difference, the different amounts of UVB. 00:27:05.842 --> 00:27:07.800 align:middle line:84% I mean, if you think about it, this is probably 00:27:07.800 --> 00:27:12.320 align:middle line:84% a 50% increase at some of these wavelengths that 00:27:12.320 --> 00:27:14.420 align:middle line:84% are really harmful to the biology, 00:27:14.420 --> 00:27:16.080 align:middle line:84% so can have a pretty dramatic effect. 00:27:16.080 --> 00:27:18.780 align:middle line:90% 00:27:18.780 --> 00:27:25.340 align:middle line:84% And so I just wanted to stress the importance of UV radiation 00:27:25.340 --> 00:27:26.820 align:middle line:90% in the ocean. 00:27:26.820 --> 00:27:29.180 align:middle line:84% And I mean, overall, it's a very small percentage 00:27:29.180 --> 00:27:31.360 align:middle line:84% of the total solar flux, if you remember, 00:27:31.360 --> 00:27:33.620 align:middle line:84% from the shape of the blackbody curve and even 00:27:33.620 --> 00:27:35.860 align:middle line:84% what was hitting the surface of the Earth. 00:27:35.860 --> 00:27:38.838 align:middle line:84% But it has huge impacts for the biological systems 00:27:38.838 --> 00:27:40.380 align:middle line:84% and the chemical systems that we look 00:27:40.380 --> 00:27:43.220 align:middle line:90% at in the upper water column. 00:27:43.220 --> 00:27:45.700 align:middle line:84% Like I mentioned before, it's primarily 00:27:45.700 --> 00:27:50.220 align:middle line:84% responsible for protein and nucleic-acid damage. 00:27:50.220 --> 00:27:53.020 align:middle line:84% It can inhibit really basic processes, like photosynthesis 00:27:53.020 --> 00:27:55.300 align:middle line:90% and bacterial production. 00:27:55.300 --> 00:27:57.660 align:middle line:84% But it can also help in a lot of photo-enzymatic repair 00:27:57.660 --> 00:28:01.300 align:middle line:84% processes, depending on the spectral composition, where 00:28:01.300 --> 00:28:03.300 align:middle line:90% you are in the water column. 00:28:03.300 --> 00:28:06.260 align:middle line:84% It also does a lot of things photochemically, 00:28:06.260 --> 00:28:08.740 align:middle line:84% which I'm not going to talk about very much today. 00:28:08.740 --> 00:28:11.260 align:middle line:84% But one of the things that it's really involved in 00:28:11.260 --> 00:28:16.447 align:middle line:84% is inorganic nitrate and nitrite photolysis. 00:28:16.447 --> 00:28:18.030 align:middle line:84% And basically, there are certain areas 00:28:18.030 --> 00:28:21.650 align:middle line:84% of the planet that always have high concentrations of nitrate, 00:28:21.650 --> 00:28:22.670 align:middle line:90% nitrite. 00:28:22.670 --> 00:28:27.110 align:middle line:84% And when the UV hits them, they form really reactive radicals 00:28:27.110 --> 00:28:30.830 align:middle line:84% that can start a chain of photochemical reactions. 00:28:30.830 --> 00:28:32.590 align:middle line:84% And something that I'll mention later 00:28:32.590 --> 00:28:35.430 align:middle line:90% is some of these UV wavelengths. 00:28:35.430 --> 00:28:39.750 align:middle line:84% They're also responsible for the reduction of iron-3 to iron-2. 00:28:39.750 --> 00:28:41.610 align:middle line:84% So they make it more bioavailable. 00:28:41.610 --> 00:28:45.070 align:middle line:84% So that's important in terms of limiting micronutrients. 00:28:45.070 --> 00:28:46.650 align:middle line:84% It also has-- on the organic level, 00:28:46.650 --> 00:28:48.710 align:middle line:84% there's a lot of organic photochemical reactions, 00:28:48.710 --> 00:28:52.350 align:middle line:84% in terms of breaking down dissolved organic matter, 00:28:52.350 --> 00:28:54.550 align:middle line:84% bleaching color-dissolved organic matter 00:28:54.550 --> 00:28:57.470 align:middle line:84% and just generally altering its structure. 00:28:57.470 --> 00:29:01.030 align:middle line:84% So the bottom line is that UV is really important in structuring 00:29:01.030 --> 00:29:05.765 align:middle line:84% our ecosystems, and its flux is dominated by ozone. 00:29:05.765 --> 00:29:07.390 align:middle line:84% So even though this is something that's 00:29:07.390 --> 00:29:09.640 align:middle line:84% happening in the environment, and it's kind of removed 00:29:09.640 --> 00:29:11.470 align:middle line:84% from what we think about in a daily basis, 00:29:11.470 --> 00:29:13.240 align:middle line:84% we really need to understand what 00:29:13.240 --> 00:29:16.360 align:middle line:84% regulates ozone concentrations to understand 00:29:16.360 --> 00:29:20.560 align:middle line:84% some of the functioning of our ecosystems. 00:29:20.560 --> 00:29:27.720 align:middle line:84% And so these are atmospheric profiles of ozone. 00:29:27.720 --> 00:29:31.320 align:middle line:84% And in the first one we have ozone number density 00:29:31.320 --> 00:29:33.560 align:middle line:90% as a function of pressure. 00:29:33.560 --> 00:29:36.100 align:middle line:84% And this first dashed line is the tropopause. 00:29:36.100 --> 00:29:39.600 align:middle line:84% And the dashed line is the top of the stratosphere, 00:29:39.600 --> 00:29:41.380 align:middle line:90% just for reference. 00:29:41.380 --> 00:29:42.880 align:middle line:84% And as you can see, there's actually 00:29:42.880 --> 00:29:46.380 align:middle line:84% quite a bit of ozone in the troposphere, 00:29:46.380 --> 00:29:50.240 align:middle line:84% but it reaches a maximum in the stratosphere. 00:29:50.240 --> 00:29:53.840 align:middle line:84% But when you look at it in terms of mixing ratio, 00:29:53.840 --> 00:29:56.200 align:middle line:84% which is parts per million by volume-- 00:29:56.200 --> 00:29:59.560 align:middle line:84% it happens to be the unit that used in this case-- 00:29:59.560 --> 00:30:02.440 align:middle line:84% there's much less in the troposphere, 00:30:02.440 --> 00:30:04.820 align:middle line:84% and it still reaches the maximum stratosphere. 00:30:04.820 --> 00:30:07.400 align:middle line:84% Basically, the way this works is that in the troposphere 00:30:07.400 --> 00:30:09.920 align:middle line:84% there's just a lot more particles. 00:30:09.920 --> 00:30:13.050 align:middle line:84% So the mixing ratio of ozone is much smaller. 00:30:13.050 --> 00:30:14.930 align:middle line:84% So it basically makes up a smaller percentage 00:30:14.930 --> 00:30:18.170 align:middle line:84% of the total particle and gas load 00:30:18.170 --> 00:30:21.450 align:middle line:84% as compared to the stratosphere, where it's actually 00:30:21.450 --> 00:30:23.730 align:middle line:90% a really large component. 00:30:23.730 --> 00:30:25.410 align:middle line:84% And as you can see, most of the ozone 00:30:25.410 --> 00:30:30.050 align:middle line:84% is actually compressed into a fairly small region, as they 00:30:30.050 --> 00:30:31.770 align:middle line:90% call it, the ozone layer. 00:30:31.770 --> 00:30:34.250 align:middle line:84% And it's on the order of about 30 kilometers 00:30:34.250 --> 00:30:36.190 align:middle line:84% into the atmosphere is where it peaks. 00:30:36.190 --> 00:30:39.610 align:middle line:90% 00:30:39.610 --> 00:30:43.807 align:middle line:84% And so I'm not going to go a lot in today 00:30:43.807 --> 00:30:45.390 align:middle line:84% into any of the atmospheric chemistry. 00:30:45.390 --> 00:30:46.843 align:middle line:84% I just wanted to show you in terms 00:30:46.843 --> 00:30:48.510 align:middle line:84% of the stratosphere and the troposphere, 00:30:48.510 --> 00:30:50.970 align:middle line:84% like the most basic reactions that 00:30:50.970 --> 00:30:53.498 align:middle line:84% are ones that-- again, it's not even so much 00:30:53.498 --> 00:30:54.790 align:middle line:90% that the details are important. 00:30:54.790 --> 00:30:56.870 align:middle line:84% You just need to understand that, for example, 00:30:56.870 --> 00:30:58.450 align:middle line:84% like the stratosphere, it's dominated 00:30:58.450 --> 00:31:02.410 align:middle line:84% by oxygen atoms and ozone-related reactions. 00:31:02.410 --> 00:31:05.010 align:middle line:84% That's what determines its temperature structure, which 00:31:05.010 --> 00:31:08.130 align:middle line:84% determines its stability, which determines 00:31:08.130 --> 00:31:11.700 align:middle line:84% the abilities of aerosols to be transported. 00:31:11.700 --> 00:31:14.380 align:middle line:84% So for example, in this case, you 00:31:14.380 --> 00:31:19.040 align:middle line:84% have oxygen. When it's hit by photons of light from the sun, 00:31:19.040 --> 00:31:23.660 align:middle line:84% it breaks down to excited-state molecular oxygen. 00:31:23.660 --> 00:31:27.260 align:middle line:84% And then this excited-state molecular oxygen 00:31:27.260 --> 00:31:32.860 align:middle line:84% can combine with another oxygen to produce ozone. 00:31:32.860 --> 00:31:35.940 align:middle line:84% And this is actually one of the most important reactions 00:31:35.940 --> 00:31:40.940 align:middle line:84% in terms of our planet and life surviving 00:31:40.940 --> 00:31:44.300 align:middle line:90% is this production of ozone. 00:31:44.300 --> 00:31:48.500 align:middle line:84% The thing, though, is that these reactions are slow. 00:31:48.500 --> 00:31:51.660 align:middle line:84% It would take on the order of maybe 20 years 00:31:51.660 --> 00:31:53.300 align:middle line:84% with these photochemical reactions 00:31:53.300 --> 00:31:56.940 align:middle line:84% to actually replace the amount of ozone we have 00:31:56.940 --> 00:31:59.900 align:middle line:90% in the atmosphere right now. 00:31:59.900 --> 00:32:04.940 align:middle line:84% They also do, as I mentioned before, something important. 00:32:04.940 --> 00:32:09.440 align:middle line:84% M is just a generic term that you use for the-- 00:32:09.440 --> 00:32:11.900 align:middle line:84% it's the third body-collision partner. 00:32:11.900 --> 00:32:14.060 align:middle line:84% It's either oxygen gas or nitrogen gas. 00:32:14.060 --> 00:32:18.960 align:middle line:84% And it's the way that the heat is dissipated. 00:32:18.960 --> 00:32:22.120 align:middle line:84% So you have these photons, these high-energy, 00:32:22.120 --> 00:32:24.880 align:middle line:84% short-wavelength photons being absorbed, 00:32:24.880 --> 00:32:26.520 align:middle line:84% and then their heat is dissipated 00:32:26.520 --> 00:32:29.720 align:middle line:84% through this third-body collision partner 00:32:29.720 --> 00:32:32.360 align:middle line:90% to the surrounding area. 00:32:32.360 --> 00:32:34.560 align:middle line:84% And so again, that's why we see that temperature 00:32:34.560 --> 00:32:36.898 align:middle line:90% profile in the stratosphere. 00:32:36.898 --> 00:32:38.440 align:middle line:84% At the top of the stratosphere, where 00:32:38.440 --> 00:32:41.920 align:middle line:84% there's more photons available to be absorbed, 00:32:41.920 --> 00:32:43.540 align:middle line:84% you're seeing more of this reaction. 00:32:43.540 --> 00:32:45.480 align:middle line:90% So more heat is dissipated. 00:32:45.480 --> 00:32:47.660 align:middle line:84% And that's why you have that temperature structure. 00:32:47.660 --> 00:32:50.560 align:middle line:90% 00:32:50.560 --> 00:32:58.400 align:middle line:84% You also then have the ability of ozone itself to absorb light, 00:32:58.400 --> 00:33:02.000 align:middle line:84% breaking it down into molecular state, excited oxygen 00:33:02.000 --> 00:33:06.450 align:middle line:90% again and then oxygen gas. 00:33:06.450 --> 00:33:09.410 align:middle line:84% And then these can combine-- the excited-state oxygen 00:33:09.410 --> 00:33:14.513 align:middle line:84% can combine with ozone to form oxygen gas again. 00:33:14.513 --> 00:33:15.930 align:middle line:84% And so what you can see from these 00:33:15.930 --> 00:33:17.990 align:middle line:90% is it's a very cyclical thing. 00:33:17.990 --> 00:33:20.870 align:middle line:84% You're not having oxygen destroyed. 00:33:20.870 --> 00:33:25.070 align:middle line:84% You're not having oxygen produced. 00:33:25.070 --> 00:33:28.930 align:middle line:90% 00:33:28.930 --> 00:33:37.010 align:middle line:84% The net of these reactions is that ozone is generally 00:33:37.010 --> 00:33:38.390 align:middle line:90% left to its own devices. 00:33:38.390 --> 00:33:42.490 align:middle line:84% It's in stable, steady-state concentration. 00:33:42.490 --> 00:33:44.550 align:middle line:84% The problem, what starts happening, though, 00:33:44.550 --> 00:33:47.890 align:middle line:84% is that ozone can be destroyed by a number 00:33:47.890 --> 00:33:52.190 align:middle line:84% of free radical catalysts that are found in the atmosphere, 00:33:52.190 --> 00:33:55.770 align:middle line:84% and these can be the hydroxyl radical, 00:33:55.770 --> 00:33:59.490 align:middle line:84% the nitric-oxide radical, chlorine or bromine. 00:33:59.490 --> 00:34:02.870 align:middle line:84% And while OH and the nitric oxide, 00:34:02.870 --> 00:34:06.300 align:middle line:84% they're predominantly natural, chlorine and bromine 00:34:06.300 --> 00:34:09.260 align:middle line:84% have anthropogenic origins in the CFCs. 00:34:09.260 --> 00:34:13.900 align:middle line:84% And that's really what motivated a lot of this research, 00:34:13.900 --> 00:34:16.239 align:middle line:84% was people started to notice the Antarctic ice hole. 00:34:16.239 --> 00:34:18.639 align:middle line:84% They started to understand the connection between CFCs. 00:34:18.639 --> 00:34:22.340 align:middle line:84% And so that's why a lot of this research was carried out. 00:34:22.340 --> 00:34:25.060 align:middle line:84% But the important thing to know about these types of cycling 00:34:25.060 --> 00:34:28.020 align:middle line:84% in the atmosphere is that there's two types of cycling. 00:34:28.020 --> 00:34:34.100 align:middle line:84% There's catalytic cycling, where you form a free radical of some 00:34:34.100 --> 00:34:38.900 align:middle line:84% and that starts off as a catalytic chain of destroying 00:34:38.900 --> 00:34:41.900 align:middle line:84% ozone or destroying odd oxygen, which 00:34:41.900 --> 00:34:45.020 align:middle line:84% is the molecularly-excited oxygen and ozone. 00:34:45.020 --> 00:34:48.380 align:middle line:84% Or there's a null cycle, which happens a lot, which basically 00:34:48.380 --> 00:34:50.900 align:middle line:84% means the chemicals in the environment 00:34:50.900 --> 00:34:53.260 align:middle line:84% are just cycling between the different pools 00:34:53.260 --> 00:34:57.340 align:middle line:84% without net loss to the odd oxygen pool. 00:34:57.340 --> 00:34:59.680 align:middle line:84% And so just depending on their interactions, 00:34:59.680 --> 00:35:01.120 align:middle line:90% they're cycling through. 00:35:01.120 --> 00:35:03.650 align:middle line:84% But we're not really losing ozone. 00:35:03.650 --> 00:35:08.270 align:middle line:90% 00:35:08.270 --> 00:35:10.470 align:middle line:84% I just wanted to talk about the Antarctic ozone 00:35:10.470 --> 00:35:14.470 align:middle line:84% hole for a little bit and what forms it and-- 00:35:14.470 --> 00:35:15.050 align:middle line:90% what? 00:35:15.050 --> 00:35:16.990 align:middle line:90% AUDIENCE: [INAUDIBLE] 00:35:16.990 --> 00:35:18.310 align:middle line:90% DIEDRE TOOLE: Yeah. 00:35:18.310 --> 00:35:19.950 align:middle line:90% It's important. 00:35:19.950 --> 00:35:22.453 align:middle line:84% So I'm just going to spend a couple slides 00:35:22.453 --> 00:35:23.870 align:middle line:84% talking about the polar ozone hole 00:35:23.870 --> 00:35:28.410 align:middle line:84% and what this means in terms of productivity and what forms it. 00:35:28.410 --> 00:35:34.710 align:middle line:90% 00:35:34.710 --> 00:35:36.790 align:middle line:84% Really, this forms because the polar region 00:35:36.790 --> 00:35:40.590 align:middle line:90% has really unique meteorology. 00:35:40.590 --> 00:35:46.630 align:middle line:84% As the polar winter, their winter, comes along, it's dark. 00:35:46.630 --> 00:35:48.190 align:middle line:90% It's completely dark. 00:35:48.190 --> 00:35:51.210 align:middle line:84% So you're not having photons hit the upper stratosphere. 00:35:51.210 --> 00:35:54.430 align:middle line:84% So you start to have a cooling in those upper stratospheric 00:35:54.430 --> 00:35:55.550 align:middle line:90% layers. 00:35:55.550 --> 00:35:57.550 align:middle line:84% And so you actually get this descending 00:35:57.550 --> 00:36:03.000 align:middle line:84% of this really cold, upper stratospheric air ascending 00:36:03.000 --> 00:36:06.360 align:middle line:90% down through the stratosphere. 00:36:06.360 --> 00:36:08.580 align:middle line:84% And so you have this very low temperature air. 00:36:08.580 --> 00:36:11.240 align:middle line:84% It's often less than negative 80 degrees 00:36:11.240 --> 00:36:15.000 align:middle line:84% C that's sort of descending down through the stratosphere. 00:36:15.000 --> 00:36:17.920 align:middle line:84% And what that allows for is for the formation 00:36:17.920 --> 00:36:21.337 align:middle line:84% of these what's known as polar stratospheric clouds. 00:36:21.337 --> 00:36:22.420 align:middle line:90% And that's really unusual. 00:36:22.420 --> 00:36:26.280 align:middle line:84% You don't expect to see particle clouds 00:36:26.280 --> 00:36:28.240 align:middle line:90% in stratosphere in this area. 00:36:28.240 --> 00:36:29.380 align:middle line:90% And there's two kinds. 00:36:29.380 --> 00:36:31.020 align:middle line:84% You can either have a water-based, 00:36:31.020 --> 00:36:34.280 align:middle line:84% which is essentially ice crystals, 00:36:34.280 --> 00:36:38.480 align:middle line:90% or nitric acid-based clouds. 00:36:38.480 --> 00:36:45.520 align:middle line:84% And so you also have a vortex of air forming 00:36:45.520 --> 00:36:47.600 align:middle line:90% as it descends in winter. 00:36:47.600 --> 00:36:49.240 align:middle line:84% And you can have this vortex form, 00:36:49.240 --> 00:36:50.980 align:middle line:84% and it can get to be extremely fast. 00:36:50.980 --> 00:36:53.150 align:middle line:84% It can get to be on the order of maybe 100 00:36:53.150 --> 00:36:56.460 align:middle line:84% meters per second in the upper atmosphere, some of the winds. 00:36:56.460 --> 00:37:00.920 align:middle line:84% So effectively you end up with a strong westerly circulation. 00:37:00.920 --> 00:37:05.260 align:middle line:84% And that's going to isolate this region from the lower latitudes. 00:37:05.260 --> 00:37:08.160 align:middle line:84% So in terms of chemistry and in terms of circulation, 00:37:08.160 --> 00:37:12.260 align:middle line:84% you have a very isolated air mass. 00:37:12.260 --> 00:37:13.440 align:middle line:90% And it's dark. 00:37:13.440 --> 00:37:19.540 align:middle line:84% So no photochemical reactions are really happening inside. 00:37:19.540 --> 00:37:21.260 align:middle line:84% But what's really interesting is that 00:37:21.260 --> 00:37:24.100 align:middle line:84% these polar stratospheric clouds, 00:37:24.100 --> 00:37:27.820 align:middle line:84% which form from the autumn until early winter, 00:37:27.820 --> 00:37:31.580 align:middle line:84% they provide a really unique surface for chemical reactions. 00:37:31.580 --> 00:37:35.580 align:middle line:84% And these surfaces usually don't exist in the stratosphere. 00:37:35.580 --> 00:37:39.660 align:middle line:90% And so what happens is that-- 00:37:39.660 --> 00:37:44.820 align:middle line:84% We have these species, the chlorine nitrate and HCl. 00:37:44.820 --> 00:37:47.020 align:middle line:84% They're known as reservoir species. 00:37:47.020 --> 00:37:48.380 align:middle line:90% They're there. 00:37:48.380 --> 00:37:50.580 align:middle line:84% They're there in fairly high concentrations. 00:37:50.580 --> 00:37:53.040 align:middle line:84% Generally, they're fairly soluble. 00:37:53.040 --> 00:37:54.680 align:middle line:90% So they'll be rained out. 00:37:54.680 --> 00:38:00.090 align:middle line:84% But they're not usually involved in a lot of the reactions. 00:38:00.090 --> 00:38:03.630 align:middle line:84% They don't usually involve destruction of ozone reactions. 00:38:03.630 --> 00:38:10.150 align:middle line:84% But what happens is that as the season progresses and you 00:38:10.150 --> 00:38:12.990 align:middle line:84% have these polar stratospheric clouds 00:38:12.990 --> 00:38:16.070 align:middle line:84% with these surface for chemical reactions, 00:38:16.070 --> 00:38:17.130 align:middle line:90% things start changing. 00:38:17.130 --> 00:38:18.870 align:middle line:84% Things start happening really fast. 00:38:18.870 --> 00:38:21.550 align:middle line:84% And one thing you notice is that this region, it's 00:38:21.550 --> 00:38:26.610 align:middle line:84% very deficient in oxides of nitrogen. So you can't form-- 00:38:26.610 --> 00:38:30.270 align:middle line:90% 00:38:30.270 --> 00:38:32.990 align:middle line:84% Once you start breaking down these compounds, 00:38:32.990 --> 00:38:35.990 align:middle line:84% they cannot go back to their null cycles, 00:38:35.990 --> 00:38:39.590 align:middle line:84% where they're just cycling through and not affecting ozone 00:38:39.590 --> 00:38:44.070 align:middle line:84% or odd oxygen. Once you have these reactions and they start 00:38:44.070 --> 00:38:47.590 align:middle line:84% to progress, you lose your nitrogen compounds, 00:38:47.590 --> 00:38:50.310 align:middle line:84% and you lose your water compounds. 00:38:50.310 --> 00:38:53.830 align:middle line:84% So they're stuck in this free radical form, 00:38:53.830 --> 00:38:55.610 align:middle line:90% which is often chlorine gas. 00:38:55.610 --> 00:38:59.960 align:middle line:84% And you can't go back on the reaction because-- 00:38:59.960 --> 00:39:01.800 align:middle line:84% and also, you have these clouds where 00:39:01.800 --> 00:39:06.160 align:middle line:84% these surface reactions are really, really enhancing this. 00:39:06.160 --> 00:39:10.120 align:middle line:84% And so what happens is you have these clouds, 00:39:10.120 --> 00:39:15.120 align:middle line:84% and you have now a lot of chlorine gas floating around, 00:39:15.120 --> 00:39:17.240 align:middle line:84% and as soon as the spring starts and you 00:39:17.240 --> 00:39:21.560 align:middle line:84% get that start of the input of the solar photons, 00:39:21.560 --> 00:39:26.360 align:middle line:84% chlorine gas disassociates into chlorine. 00:39:26.360 --> 00:39:28.320 align:middle line:84% And chlorine can react with ozone 00:39:28.320 --> 00:39:32.360 align:middle line:84% to form chlorine oxide, which is another highly-reactive radical, 00:39:32.360 --> 00:39:36.880 align:middle line:84% which can react with ozone and oxygen. 00:39:36.880 --> 00:39:42.400 align:middle line:84% And then you have chlorine oxide reacting with oxygen, again, 00:39:42.400 --> 00:39:47.720 align:middle line:84% to form chlorine gas and oxygen. And what you can see from this 00:39:47.720 --> 00:39:52.560 align:middle line:84% is your chlorine through these two steps. 00:39:52.560 --> 00:39:54.610 align:middle line:90% It's regenerated. 00:39:54.610 --> 00:39:55.830 align:middle line:90% So you started with it. 00:39:55.830 --> 00:39:56.910 align:middle line:90% It had its reactions. 00:39:56.910 --> 00:40:00.510 align:middle line:84% And then at the end, it's still available to react. 00:40:00.510 --> 00:40:02.610 align:middle line:84% It hasn't been bound to anything. 00:40:02.610 --> 00:40:05.250 align:middle line:84% So it's still available to go through these reactions. 00:40:05.250 --> 00:40:08.470 align:middle line:84% And you also see that there's this destruction of odd oxygen. 00:40:08.470 --> 00:40:12.050 align:middle line:84% You started with your ozone and your molecularly-excited atomic 00:40:12.050 --> 00:40:16.450 align:middle line:84% oxygen, and you ended up with two oxygens. 00:40:16.450 --> 00:40:21.510 align:middle line:84% So you have this destruction of the single molecule of ozone, 00:40:21.510 --> 00:40:23.730 align:middle line:84% but your chlorine is still there. 00:40:23.730 --> 00:40:28.530 align:middle line:84% And so it can go off, and it can react with ozone again. 00:40:28.530 --> 00:40:30.810 align:middle line:84% And so this is a catalyzed reaction, 00:40:30.810 --> 00:40:34.090 align:middle line:84% where the chlorine can just keep cranking through the ozone 00:40:34.090 --> 00:40:41.850 align:middle line:84% molecules until something happens to get the chlorine out 00:40:41.850 --> 00:40:42.990 align:middle line:90% of this gas phase. 00:40:42.990 --> 00:40:48.470 align:middle line:84% And generally what happens is that in the late spring, 00:40:48.470 --> 00:40:50.130 align:middle line:90% the vortex breaks up. 00:40:50.130 --> 00:40:51.030 align:middle line:90% The sun comes out. 00:40:51.030 --> 00:40:52.870 align:middle line:90% It gets warmer. 00:40:52.870 --> 00:40:56.270 align:middle line:84% You start to melt your cloud particles. 00:40:56.270 --> 00:41:00.830 align:middle line:84% So a lot of the water and the nitrogen that were frozen now 00:41:00.830 --> 00:41:07.030 align:middle line:84% are available to react with the chlorine to form soluble gases. 00:41:07.030 --> 00:41:09.710 align:middle line:84% You can get back to your reservoir compounds 00:41:09.710 --> 00:41:14.110 align:middle line:84% essentially in the late winter, early spring. 00:41:14.110 --> 00:41:18.190 align:middle line:84% They get back into the melting clouds, and they're rained out. 00:41:18.190 --> 00:41:22.050 align:middle line:84% And so just to convince you that this actually happens, 00:41:22.050 --> 00:41:27.350 align:middle line:84% these are images from an Antarctic cruise that I was on. 00:41:27.350 --> 00:41:28.750 align:middle line:90% There from TOMS. 00:41:28.750 --> 00:41:29.610 align:middle line:90% That's a satellite. 00:41:29.610 --> 00:41:33.270 align:middle line:84% It's the total ozone mapping spectrometer. 00:41:33.270 --> 00:41:37.150 align:middle line:84% And it basically looks at column-integrated ozone. 00:41:37.150 --> 00:41:41.810 align:middle line:84% And it presents results in terms of Dobson units, loss of scale. 00:41:41.810 --> 00:41:42.830 align:middle line:90% That's interesting. 00:41:42.830 --> 00:41:44.590 align:middle line:84% And basically, what Dobson unit is, 00:41:44.590 --> 00:41:46.647 align:middle line:84% is if you take the entire column of ozone 00:41:46.647 --> 00:41:48.730 align:middle line:84% through the troposphere, through the stratosphere, 00:41:48.730 --> 00:41:51.640 align:middle line:84% and you compress it down to standard temperature 00:41:51.640 --> 00:41:54.120 align:middle line:84% and pressure, one Dobson unit would 00:41:54.120 --> 00:41:57.360 align:middle line:84% mean that it's about 10 microns thick. 00:41:57.360 --> 00:42:00.640 align:middle line:84% So pretty much a standard Dobson unit concentration 00:42:00.640 --> 00:42:05.960 align:middle line:84% for Antarctica when there's not an ozone hole is maybe 300, 350. 00:42:05.960 --> 00:42:10.880 align:middle line:84% And under the ozone hole, which is represented by the-- 00:42:10.880 --> 00:42:12.680 align:middle line:90% can I play it again? 00:42:12.680 --> 00:42:15.760 align:middle line:84% by the more blue purple colors here, 00:42:15.760 --> 00:42:19.260 align:middle line:84% you can start to see the formation of the polar vortex, 00:42:19.260 --> 00:42:23.220 align:middle line:84% and the air being cordoned off from the surrounding air. 00:42:23.220 --> 00:42:26.360 align:middle line:84% But you can also see, as it turns more and more purple, 00:42:26.360 --> 00:42:28.600 align:middle line:84% that you're having lower and lower ozone 00:42:28.600 --> 00:42:31.000 align:middle line:84% concentrations because of that catalytic destruction 00:42:31.000 --> 00:42:32.020 align:middle line:90% of chlorine. 00:42:32.020 --> 00:42:34.680 align:middle line:90% 00:42:34.680 --> 00:42:36.220 align:middle line:90% Does anybody have any questions? 00:42:36.220 --> 00:42:36.940 align:middle line:90% Ready to move on? 00:42:36.940 --> 00:42:37.520 align:middle line:90% Yeah. 00:42:37.520 --> 00:42:39.600 align:middle line:84% AUDIENCE: Could you go over again, just briefly, 00:42:39.600 --> 00:42:44.000 align:middle line:84% how you initially get the chlorine 00:42:44.000 --> 00:42:47.960 align:middle line:84% gas in the state where it then can react with [INAUDIBLE]? 00:42:47.960 --> 00:42:52.290 align:middle line:84% I misunderstood because I think I first thought that it 00:42:52.290 --> 00:42:55.770 align:middle line:90% was initialized by like-- 00:42:55.770 --> 00:42:56.670 align:middle line:90% DIEDRE TOOLE: Oh, OK. 00:42:56.670 --> 00:43:02.210 align:middle line:84% What happens is these two reservoir species actually 00:43:02.210 --> 00:43:06.690 align:middle line:84% interact, collide with one of the polar stratospheric clouds. 00:43:06.690 --> 00:43:10.910 align:middle line:84% And what you lose out-- for example, for this first one, 00:43:10.910 --> 00:43:14.410 align:middle line:84% you lose out a nitric acid that would essentially 00:43:14.410 --> 00:43:16.970 align:middle line:84% react and become the solid on the cloud. 00:43:16.970 --> 00:43:19.290 align:middle line:84% And you'd have liberation of chlorine gas. 00:43:19.290 --> 00:43:20.050 align:middle line:90% AUDIENCE: OK. 00:43:20.050 --> 00:43:20.590 align:middle line:90% Thank you. 00:43:20.590 --> 00:43:22.210 align:middle line:84% DIEDRE TOOLE: And that doesn't need 00:43:22.210 --> 00:43:24.265 align:middle line:90% to involve light in any way. 00:43:24.265 --> 00:43:25.890 align:middle line:84% It's as soon as-- and once you-- and so 00:43:25.890 --> 00:43:27.850 align:middle line:90% you're going to have a buildup. 00:43:27.850 --> 00:43:30.730 align:middle line:84% And you can see that of these chlorine gas 00:43:30.730 --> 00:43:33.350 align:middle line:84% in time until you get enough light. 00:43:33.350 --> 00:43:36.090 align:middle line:90% 00:43:36.090 --> 00:43:38.090 align:middle line:90% Anyone else? 00:43:38.090 --> 00:43:38.590 align:middle line:90% OK. 00:43:38.590 --> 00:43:39.970 align:middle line:90% I'm going to get moving here. 00:43:39.970 --> 00:43:41.330 align:middle line:90% Wait. 00:43:41.330 --> 00:43:42.710 align:middle line:84% How do I get past this with them? 00:43:42.710 --> 00:43:44.570 align:middle line:90% OK. 00:43:44.570 --> 00:43:47.700 align:middle line:84% Oh, just to go over this really quickly, 00:43:47.700 --> 00:43:51.340 align:middle line:84% I just wanted to let you know that in the troposphere, 00:43:51.340 --> 00:43:55.620 align:middle line:84% there's predominantly two types of photochemical reactions 00:43:55.620 --> 00:43:58.140 align:middle line:90% that happen. 00:43:58.140 --> 00:44:02.220 align:middle line:90% The first part is-- 00:44:02.220 --> 00:44:04.540 align:middle line:84% it's a daytime-nighttime split is essentially 00:44:04.540 --> 00:44:07.540 align:middle line:84% how most of the tropospheric reactions work. 00:44:07.540 --> 00:44:09.940 align:middle line:84% And the oxidation reactions during the day 00:44:09.940 --> 00:44:13.780 align:middle line:84% are generally initiated by the highly-reactive hydroxyl 00:44:13.780 --> 00:44:14.980 align:middle line:90% radical. 00:44:14.980 --> 00:44:17.640 align:middle line:84% It has a lifetime on the order of a couple seconds. 00:44:17.640 --> 00:44:20.980 align:middle line:84% So as soon as it's formed, it's going to react. 00:44:20.980 --> 00:44:23.780 align:middle line:84% And basically the way that we get that in the troposphere 00:44:23.780 --> 00:44:28.420 align:middle line:84% is from the reaction of ozone within the troposphere itself. 00:44:28.420 --> 00:44:30.900 align:middle line:84% Plus, light leads again to oxygen 00:44:30.900 --> 00:44:33.940 align:middle line:84% and the molecular state-excited oxygen. 00:44:33.940 --> 00:44:37.260 align:middle line:84% And then this reacts with a normal greenhouse gases 00:44:37.260 --> 00:44:41.020 align:middle line:84% that we're used to, like water, methane, 00:44:41.020 --> 00:44:44.100 align:middle line:84% and you produce these hydroxyl radicals. 00:44:44.100 --> 00:44:48.790 align:middle line:84% There's a host of thousands of different types of chain 00:44:48.790 --> 00:44:50.512 align:middle line:90% reactions and things that go on. 00:44:50.512 --> 00:44:52.970 align:middle line:84% But the most important thing to know is just during the day 00:44:52.970 --> 00:44:56.550 align:middle line:84% it's the OH radical that's determining the chemistry 00:44:56.550 --> 00:44:57.870 align:middle line:90% and what's going on. 00:44:57.870 --> 00:45:00.470 align:middle line:84% And at night-- obviously we can't 00:45:00.470 --> 00:45:04.590 align:middle line:84% have this reaction happening at night because there's no light. 00:45:04.590 --> 00:45:09.070 align:middle line:84% And so at night, it's nitrate radicals 00:45:09.070 --> 00:45:11.910 align:middle line:84% that are formed from the nitrogen dioxide combining 00:45:11.910 --> 00:45:14.190 align:middle line:90% with ozone. 00:45:14.190 --> 00:45:16.670 align:middle line:84% And that produces these nitrate radicals. 00:45:16.670 --> 00:45:22.350 align:middle line:84% And that initiates most of the chemical reactions 00:45:22.350 --> 00:45:23.530 align:middle line:90% that happen at night. 00:45:23.530 --> 00:45:26.910 align:middle line:84% And these two radical species govern 00:45:26.910 --> 00:45:30.570 align:middle line:84% the fates of almost all the trace gases in the troposphere. 00:45:30.570 --> 00:45:34.790 align:middle line:90% 00:45:34.790 --> 00:45:37.510 align:middle line:84% Does this show you a summary of what 00:45:37.510 --> 00:45:40.870 align:middle line:84% we've talked about so far in terms of radiative 00:45:40.870 --> 00:45:43.310 align:middle line:90% forcing at the Earth's surface? 00:45:43.310 --> 00:45:47.370 align:middle line:84% What this is, is it's IPCC estimates 00:45:47.370 --> 00:45:51.490 align:middle line:84% of the mean radiative forcing of the climate system for the year 00:45:51.490 --> 00:45:54.410 align:middle line:90% 2000 relative to 1750. 00:45:54.410 --> 00:45:57.570 align:middle line:84% So it's, how much has this changed over the course 00:45:57.570 --> 00:45:59.410 align:middle line:90% of this 250 years? 00:45:59.410 --> 00:46:04.450 align:middle line:84% The x-axis really is just our level of scientific certainty. 00:46:04.450 --> 00:46:08.590 align:middle line:84% And they range from high to low to very, very low. 00:46:08.590 --> 00:46:10.370 align:middle line:90% They should be more specific. 00:46:10.370 --> 00:46:15.350 align:middle line:84% And in terms of the y-axis, it's radiative forcing, 00:46:15.350 --> 00:46:17.370 align:middle line:90% which is watts per square meter. 00:46:17.370 --> 00:46:20.570 align:middle line:84% So if your radiative forcing is positive, 00:46:20.570 --> 00:46:21.710 align:middle line:90% that means you're warming. 00:46:21.710 --> 00:46:24.850 align:middle line:84% That means more of the photons are actually 00:46:24.850 --> 00:46:29.663 align:middle line:84% reaching the surface of the Earth, whereas-- 00:46:29.663 --> 00:46:31.330 align:middle line:84% AUDIENCE: It's not coming-- most of them 00:46:31.330 --> 00:46:32.670 align:middle line:84% are come-- from the greenhouse gases. 00:46:32.670 --> 00:46:33.390 align:middle line:84% DIEDRE TOOLE: Well, most of them are. 00:46:33.390 --> 00:46:34.030 align:middle line:90% Yeah. 00:46:34.030 --> 00:46:35.697 align:middle line:84% But it depends on which one specifically 00:46:35.697 --> 00:46:36.650 align:middle line:90% you're talking about. 00:46:36.650 --> 00:46:38.150 align:middle line:84% Well, OK, we'll just say in general. 00:46:38.150 --> 00:46:40.590 align:middle line:84% If you're radiative forcing is considered positive, 00:46:40.590 --> 00:46:42.310 align:middle line:84% it's warming because Scott's right. 00:46:42.310 --> 00:46:47.260 align:middle line:84% These are photons being emitted from the Earth 00:46:47.260 --> 00:46:49.820 align:middle line:84% and trapped by the greenhouse gases, 00:46:49.820 --> 00:46:52.580 align:middle line:84% whereas if your radiative forcing, it's cooling, 00:46:52.580 --> 00:46:53.260 align:middle line:90% is negative. 00:46:53.260 --> 00:46:53.760 align:middle line:90% Excuse me. 00:46:53.760 --> 00:46:55.180 align:middle line:90% That's cooling. 00:46:55.180 --> 00:46:58.860 align:middle line:84% And so for example, in terms of stratospheric ozone, 00:46:58.860 --> 00:47:01.580 align:middle line:84% that's more the incoming solar photons 00:47:01.580 --> 00:47:03.660 align:middle line:90% that we're concerned about. 00:47:03.660 --> 00:47:07.550 align:middle line:84% So we can see in the last 250 years, because of the ozone hole 00:47:07.550 --> 00:47:09.300 align:middle line:84% that we just talked about, we've lost some 00:47:09.300 --> 00:47:12.100 align:middle line:90% of the stratospheric ozone. 00:47:12.100 --> 00:47:16.060 align:middle line:84% So more of the cooling is happening because we're not 00:47:16.060 --> 00:47:18.780 align:middle line:84% getting that absorption by the ozone of those photons 00:47:18.780 --> 00:47:23.100 align:middle line:84% and warming the stratosphere, whereas the opposite is the case 00:47:23.100 --> 00:47:26.448 align:middle line:90% for tropospheric ozone. 00:47:26.448 --> 00:47:28.740 align:middle line:84% And the one thing that I just wanted to show about this 00:47:28.740 --> 00:47:31.660 align:middle line:84% is that our uncertainty in a lot of these 00:47:31.660 --> 00:47:35.120 align:middle line:84% processes, we understand the physics of them, 00:47:35.120 --> 00:47:36.320 align:middle line:90% that they're happening. 00:47:36.320 --> 00:47:39.260 align:middle line:84% But in terms of quantifying them and coming up 00:47:39.260 --> 00:47:42.450 align:middle line:84% with a magnitude for their exact effect on the radiation budget, 00:47:42.450 --> 00:47:44.070 align:middle line:90% it's pretty uncertain. 00:47:44.070 --> 00:47:46.630 align:middle line:84% I mean, you can see for the aerosol indirect effect, which 00:47:46.630 --> 00:47:49.350 align:middle line:84% is the clouds, so about the formation of the clouds 00:47:49.350 --> 00:47:55.610 align:middle line:84% and reflecting back to space, we don't even have a mean estimate. 00:47:55.610 --> 00:47:56.810 align:middle line:90% We just have an error bar. 00:47:56.810 --> 00:48:00.070 align:middle line:84% So there's lots of other effects on here too, that I haven't 00:48:00.070 --> 00:48:02.670 align:middle line:84% talked about today, and I won't talk about today, that can 00:48:02.670 --> 00:48:04.630 align:middle line:90% affect the radiation budget. 00:48:04.630 --> 00:48:08.910 align:middle line:84% And some of that is airplanes flying 00:48:08.910 --> 00:48:12.830 align:middle line:84% in the stratosphere, volatile organic carbon species. 00:48:12.830 --> 00:48:19.270 align:middle line:84% I'm just going to try to stick to a few of these to talk about. 00:48:19.270 --> 00:48:23.310 align:middle line:84% So now I want to show you some examples of compounds that 00:48:23.310 --> 00:48:26.470 align:middle line:84% originate in the ocean, or compounds 00:48:26.470 --> 00:48:28.330 align:middle line:84% that are being injected into the ocean, 00:48:28.330 --> 00:48:33.278 align:middle line:84% and how that's affecting these feedback loops. 00:48:33.278 --> 00:48:35.070 align:middle line:84% And the first thing I'm going to talk about 00:48:35.070 --> 00:48:36.903 align:middle line:84% is something very near and dear to my heart. 00:48:36.903 --> 00:48:40.400 align:middle line:90% It's the biogenic sulfur cycle. 00:48:40.400 --> 00:48:49.340 align:middle line:84% So basically the way this works is you have a gas, a sulfur gas. 00:48:49.340 --> 00:48:50.620 align:middle line:90% It's dimethyl sulfide. 00:48:50.620 --> 00:48:53.960 align:middle line:84% It's a reduced sulfur gas produced through a host 00:48:53.960 --> 00:48:58.320 align:middle line:84% biological interactions, phytoplankton reactions, 00:48:58.320 --> 00:49:00.040 align:middle line:90% bacteria, zooplankton. 00:49:00.040 --> 00:49:02.960 align:middle line:84% But the end result is that you have a ventilation 00:49:02.960 --> 00:49:04.360 align:middle line:90% to the atmosphere. 00:49:04.360 --> 00:49:07.160 align:middle line:84% So you have DMS gas free in the atmosphere. 00:49:07.160 --> 00:49:09.180 align:middle line:84% And this is still within that boundary layer, 00:49:09.180 --> 00:49:12.040 align:middle line:84% that first kilometer we talked about. 00:49:12.040 --> 00:49:14.720 align:middle line:84% But what happens once it gets into the boundary layer 00:49:14.720 --> 00:49:17.000 align:middle line:84% is it goes through a lot of photochemical oxidation 00:49:17.000 --> 00:49:17.722 align:middle line:90% reactions. 00:49:17.722 --> 00:49:20.180 align:middle line:84% I'm not going to give you the exact specifics on those here 00:49:20.180 --> 00:49:21.020 align:middle line:90% today. 00:49:21.020 --> 00:49:24.760 align:middle line:84% It goes to sulfur dioxide, which can eventually be 00:49:24.760 --> 00:49:28.400 align:middle line:90% processed to sulfate aerosols. 00:49:28.400 --> 00:49:31.680 align:middle line:84% So like we talked about originally, sulfate 00:49:31.680 --> 00:49:35.560 align:middle line:84% aerosols in the atmosphere, they can have a direct effect. 00:49:35.560 --> 00:49:39.770 align:middle line:84% They'll directly scatter some of the sunlight back to space, 00:49:39.770 --> 00:49:42.390 align:middle line:84% based on their scattering geometry, 00:49:42.390 --> 00:49:44.210 align:middle line:90% the size of the particle. 00:49:44.210 --> 00:49:49.810 align:middle line:84% They also provide a surface for the clouds to condense on. 00:49:49.810 --> 00:49:51.530 align:middle line:84% So as soon as you have sulfate aerosols, 00:49:51.530 --> 00:49:53.530 align:middle line:84% you're going to have the water droplets starting 00:49:53.530 --> 00:49:54.430 align:middle line:90% to condense on them. 00:49:54.430 --> 00:49:56.410 align:middle line:84% And they're going to effectively act 00:49:56.410 --> 00:49:59.170 align:middle line:90% as cloud condensation nuclei. 00:49:59.170 --> 00:50:01.850 align:middle line:84% And so once you get more CCNs, that 00:50:01.850 --> 00:50:04.890 align:middle line:84% increases your number concentration of droplets 00:50:04.890 --> 00:50:06.930 align:middle line:90% and your cloud albedo. 00:50:06.930 --> 00:50:10.870 align:middle line:84% There's a whole host of cloud microphysics that go into that. 00:50:10.870 --> 00:50:13.650 align:middle line:84% But ultimately, what happens is that you increase the cloud 00:50:13.650 --> 00:50:19.130 align:middle line:84% albedo, which makes the Earth's surface more reflective. 00:50:19.130 --> 00:50:21.930 align:middle line:84% And if you think about it, this is a gas 00:50:21.930 --> 00:50:24.410 align:middle line:90% that's emitted from the ocean. 00:50:24.410 --> 00:50:27.930 align:middle line:84% And as I said earlier, the oceans are really dark target. 00:50:27.930 --> 00:50:32.730 align:middle line:84% I mean, it's nearly 95%, 98% absorption. 00:50:32.730 --> 00:50:34.490 align:middle line:84% So if you take a bright white cloud 00:50:34.490 --> 00:50:36.510 align:middle line:84% and stick it on top of that, you can 00:50:36.510 --> 00:50:39.990 align:middle line:84% have a pretty dramatic effect on the radiation budget. 00:50:39.990 --> 00:50:43.550 align:middle line:84% And this is especially so in large areas 00:50:43.550 --> 00:50:45.950 align:middle line:84% of the southern hemisphere, where you really 00:50:45.950 --> 00:50:50.150 align:middle line:84% are far away from any of anthropogenic sulfur inputs. 00:50:50.150 --> 00:50:54.230 align:middle line:84% Aerosols are primarily from these marine sources. 00:50:54.230 --> 00:50:55.847 align:middle line:84% So what we need to understand and what 00:50:55.847 --> 00:50:57.430 align:middle line:84% we're trying to understand is, once we 00:50:57.430 --> 00:51:00.830 align:middle line:84% have this change in clouds, in the cloud albedo, 00:51:00.830 --> 00:51:03.290 align:middle line:84% we're going to have less of the solar radiation, 00:51:03.290 --> 00:51:05.910 align:middle line:84% less of the photons from the sun actually reaching 00:51:05.910 --> 00:51:08.030 align:middle line:90% the surface of the Earth. 00:51:08.030 --> 00:51:09.630 align:middle line:84% But we don't really necessarily know 00:51:09.630 --> 00:51:13.870 align:middle line:84% is how that affects the surface temperature of the Earth. 00:51:13.870 --> 00:51:16.310 align:middle line:84% You have less photons reaching the surface of the Earth 00:51:16.310 --> 00:51:18.150 align:middle line:84% because the clouds are reflecting them back. 00:51:18.150 --> 00:51:20.790 align:middle line:84% That's going to decrease the temperature of the Earth. 00:51:20.790 --> 00:51:24.390 align:middle line:84% That's also going to decrease, obviously, the irradiance. 00:51:24.390 --> 00:51:27.350 align:middle line:84% And so what this cycle tells us that, though, 00:51:27.350 --> 00:51:30.170 align:middle line:84% where the understanding isn't there yet, 00:51:30.170 --> 00:51:34.110 align:middle line:84% is how that feeds back in to affect the marine ecology 00:51:34.110 --> 00:51:36.000 align:middle line:84% and how that affects the phytoplankton 00:51:36.000 --> 00:51:38.840 align:middle line:84% abundances or the speciation, which eventually then 00:51:38.840 --> 00:51:42.760 align:middle line:84% is going to feed back into how much DMS gas is there 00:51:42.760 --> 00:51:46.600 align:middle line:90% to be injected back to space. 00:51:46.600 --> 00:51:50.200 align:middle line:84% A couple of things in terms of sulfur budgets to notice 00:51:50.200 --> 00:51:52.800 align:middle line:84% is that these sulfate aerosols, they 00:51:52.800 --> 00:51:55.240 align:middle line:84% affect the atmospheric acidity, which I'll 00:51:55.240 --> 00:51:56.580 align:middle line:90% talk about in a couple slides. 00:51:56.580 --> 00:51:59.040 align:middle line:90% So they contribute to acid rain. 00:51:59.040 --> 00:52:01.080 align:middle line:84% They also kind of are the main reason 00:52:01.080 --> 00:52:03.120 align:middle line:84% that people started studying them 00:52:03.120 --> 00:52:08.943 align:middle line:84% is that they affect the sulfur transport to continents to land. 00:52:08.943 --> 00:52:10.360 align:middle line:84% It's a way, essentially for sulfur 00:52:10.360 --> 00:52:13.120 align:middle line:84% to get out of the ocean into the atmosphere 00:52:13.120 --> 00:52:16.040 align:middle line:84% and then through wet deposition of these aerosols, which 00:52:16.040 --> 00:52:20.080 align:middle line:84% is essentially being rained out to contribute them to land. 00:52:20.080 --> 00:52:23.320 align:middle line:84% They're also involved in an autocatalytic destruction 00:52:23.320 --> 00:52:24.580 align:middle line:90% of ozone cycle. 00:52:24.580 --> 00:52:31.600 align:middle line:90% 00:52:31.600 --> 00:52:36.410 align:middle line:84% But in terms of assessing the importance of this cycle 00:52:36.410 --> 00:52:40.410 align:middle line:84% on biology and upper ocean chemistry, one thing 00:52:40.410 --> 00:52:45.770 align:middle line:84% we always need to consider, and we really have to keep in mind, 00:52:45.770 --> 00:52:48.850 align:middle line:84% especially these days, is fluxes in terms 00:52:48.850 --> 00:52:53.770 align:middle line:84% of natural biological fluxes versus anthropogenic fluxes 00:52:53.770 --> 00:52:56.970 align:middle line:84% and how they feed back onto one another. 00:52:56.970 --> 00:53:02.610 align:middle line:84% So we do know that this oceanic source of sulfur gas, 00:53:02.610 --> 00:53:03.750 align:middle line:90% it's ubiquitous. 00:53:03.750 --> 00:53:07.850 align:middle line:84% It represents over greater than 50% of the oceanic sulfur flux 00:53:07.850 --> 00:53:12.193 align:middle line:84% to the atmosphere and greater than 50% of the biogenic flux. 00:53:12.193 --> 00:53:13.610 align:middle line:84% But we need to understand how that 00:53:13.610 --> 00:53:16.970 align:middle line:84% relates to anthropogenic flux, to put it in context. 00:53:16.970 --> 00:53:22.050 align:middle line:84% And we know that the estimated anthropogenic flux of sulfur, 00:53:22.050 --> 00:53:26.090 align:middle line:84% it's probably about three times larger than the biogenic sources 00:53:26.090 --> 00:53:27.610 align:middle line:90% of sulfur. 00:53:27.610 --> 00:53:32.133 align:middle line:84% But what we do know is that the lifetimes are much shorter. 00:53:32.133 --> 00:53:35.420 align:middle line:84% Because when DMS comes out of the ocean, 00:53:35.420 --> 00:53:37.820 align:middle line:90% it's a highly reduced form. 00:53:37.820 --> 00:53:41.580 align:middle line:84% And so it has to go through a lot of oxidation steps 00:53:41.580 --> 00:53:45.540 align:middle line:84% before it can reach a form that can form an aerosol 00:53:45.540 --> 00:53:48.300 align:middle line:84% and can condense into a cloud and be rained out. 00:53:48.300 --> 00:53:51.260 align:middle line:84% In contrast to this, a lot of the anthropogenic sources 00:53:51.260 --> 00:53:57.580 align:middle line:84% such as the oil refining, coal and oil combustion, sulfur 00:53:57.580 --> 00:54:01.060 align:middle line:84% is emitted immediately as sulfur dioxide. 00:54:01.060 --> 00:54:03.840 align:middle line:84% And so really what happens is it goes up as sulfur dioxide. 00:54:03.840 --> 00:54:05.400 align:middle line:90% And it's a very regional effect. 00:54:05.400 --> 00:54:10.660 align:middle line:84% A lot of it can be rained out fairly locally to the point 00:54:10.660 --> 00:54:13.060 align:middle line:90% source. 00:54:13.060 --> 00:54:16.300 align:middle line:84% Other sources of sulfur for the troposphere 00:54:16.300 --> 00:54:18.340 align:middle line:90% are the decay of vegetation. 00:54:18.340 --> 00:54:20.820 align:middle line:84% It's a little bit less, but very similar 00:54:20.820 --> 00:54:26.460 align:middle line:84% in magnitude to that of oceanic sources, and also sea spray, 00:54:26.460 --> 00:54:29.220 align:middle line:84% which I'll talk a little bit about later. 00:54:29.220 --> 00:54:31.410 align:middle line:84% Volcanoes are a really interesting source 00:54:31.410 --> 00:54:34.270 align:middle line:84% because they're one of the ways that sulfur can actually get 00:54:34.270 --> 00:54:36.550 align:middle line:90% injected into the stratosphere. 00:54:36.550 --> 00:54:40.990 align:middle line:84% They can inject sulfur dioxide directly to the stratosphere 00:54:40.990 --> 00:54:43.470 align:middle line:84% because really, the issue with a lot of sulfur compounds 00:54:43.470 --> 00:54:45.710 align:middle line:84% is that most of them are too soluble or too 00:54:45.710 --> 00:54:48.690 align:middle line:84% reactive to make it that high up in the atmosphere. 00:54:48.690 --> 00:54:51.790 align:middle line:84% There's one exception, which I'll talk about in a second. 00:54:51.790 --> 00:54:56.950 align:middle line:84% But in terms of us and radiation forcing and understanding 00:54:56.950 --> 00:54:59.790 align:middle line:84% that feedback system, the important thing to know 00:54:59.790 --> 00:55:02.710 align:middle line:84% is that when you look at the upper troposphere, 00:55:02.710 --> 00:55:05.670 align:middle line:84% the upper tropospheric levels, less than 20% 00:55:05.670 --> 00:55:07.470 align:middle line:84% of the sulfate aerosols in the sulfur 00:55:07.470 --> 00:55:10.190 align:middle line:84% dioxide at those altitudes are derived 00:55:10.190 --> 00:55:12.070 align:middle line:90% from anthropogenic sources. 00:55:12.070 --> 00:55:15.970 align:middle line:84% More than 80% is derived from biogenic sources, 00:55:15.970 --> 00:55:19.610 align:middle line:84% which I said the decay of terrestrial organic matter, 00:55:19.610 --> 00:55:20.410 align:middle line:90% the DMS. 00:55:20.410 --> 00:55:25.630 align:middle line:90% 00:55:25.630 --> 00:55:30.490 align:middle line:84% I just wanted to, again, reiterate that DMS does impact 00:55:30.490 --> 00:55:33.470 align:middle line:84% the atmospheric chemistry pretty substantially. 00:55:33.470 --> 00:55:35.450 align:middle line:84% There's a lot of cyclical reactions 00:55:35.450 --> 00:55:37.450 align:middle line:84% and a lot of complex reactions, but I just 00:55:37.450 --> 00:55:42.050 align:middle line:84% wanted to say the main take home message is that DMS reacts 00:55:42.050 --> 00:55:46.050 align:middle line:84% in the troposphere with the OH radical during the day 00:55:46.050 --> 00:55:48.890 align:middle line:84% and the nitrate radical at night, which is fairly typical 00:55:48.890 --> 00:55:51.930 align:middle line:84% of most chemical reactions in the troposphere. 00:55:51.930 --> 00:55:56.930 align:middle line:84% And it's formed the sulfur dioxide. 00:55:56.930 --> 00:55:59.030 align:middle line:84% But there's also another interesting species. 00:55:59.030 --> 00:56:01.010 align:middle line:84% There's a way you can get through this way, 00:56:01.010 --> 00:56:03.530 align:middle line:90% is carbonyl sulfide. 00:56:03.530 --> 00:56:06.610 align:middle line:90% And this can be formed from DMS. 00:56:06.610 --> 00:56:08.730 align:middle line:84% And this is the only species of sulfur 00:56:08.730 --> 00:56:11.690 align:middle line:84% that can actually make it up to the stratosphere. 00:56:11.690 --> 00:56:14.810 align:middle line:84% And that's because it has a really long lifetime. 00:56:14.810 --> 00:56:20.050 align:middle line:84% And one way that we know that is that-- 00:56:20.050 --> 00:56:23.010 align:middle line:84% you can assess the lifetimes of things in the atmosphere 00:56:23.010 --> 00:56:25.210 align:middle line:90% based on their distribution. 00:56:25.210 --> 00:56:30.460 align:middle line:84% If you look at a chemical, and it's very well mixed, 00:56:30.460 --> 00:56:33.100 align:middle line:84% and its distribution looks pretty uniform, especially 00:56:33.100 --> 00:56:36.620 align:middle line:84% relative to very non-uniform point sources, 00:56:36.620 --> 00:56:39.100 align:middle line:84% you can say that it has a really long lifetime. 00:56:39.100 --> 00:56:41.177 align:middle line:90% And that's the case with COS. 00:56:41.177 --> 00:56:42.760 align:middle line:84% If you look in the upper stratosphere, 00:56:42.760 --> 00:56:44.780 align:middle line:90% it's completely well mixed. 00:56:44.780 --> 00:56:48.860 align:middle line:84% And it's found pretty much throughout the globe. 00:56:48.860 --> 00:56:52.440 align:middle line:84% I mean, it has a very low gas phase reactivity, too. 00:56:52.440 --> 00:56:56.740 align:middle line:84% So it's pretty much considered that-- 00:56:56.740 --> 00:56:59.260 align:middle line:84% it's the background atmospheric levels 00:56:59.260 --> 00:57:02.300 align:middle line:84% of methane, sulfonic acid, sulfur dioxide, 00:57:02.300 --> 00:57:04.765 align:middle line:84% and non-sea-salt sulfate in the stratosphere. 00:57:04.765 --> 00:57:06.140 align:middle line:84% And basically what that's telling 00:57:06.140 --> 00:57:09.020 align:middle line:84% us is that's the way that sulfur forms aerosols 00:57:09.020 --> 00:57:14.380 align:middle line:84% in the stratosphere, is through this compound, this compound. 00:57:14.380 --> 00:57:17.460 align:middle line:84% And also, just kind of as a side, an interesting note, 00:57:17.460 --> 00:57:22.220 align:middle line:84% is that in the North Sea region, these biological fluxes 00:57:22.220 --> 00:57:24.740 align:middle line:84% of sulfur, they can account for up to 25% 00:57:24.740 --> 00:57:28.910 align:middle line:84% of the tropospheric sulfate aerosols over Europe. 00:57:28.910 --> 00:57:33.510 align:middle line:84% So still, their anthropogenic sources are having a big impact. 00:57:33.510 --> 00:57:35.750 align:middle line:84% AUDIENCE: What's the relative contribution? 00:57:35.750 --> 00:57:39.190 align:middle line:84% I mean, carbonyl sulfide is also formed within the water column. 00:57:39.190 --> 00:57:39.990 align:middle line:90% DIEDRE TOOLE: Yes. 00:57:39.990 --> 00:57:41.740 align:middle line:84% AUDIENCE: What's the relative contribution 00:57:41.740 --> 00:57:43.870 align:middle line:84% of that pathway versus [INAUDIBLE]? 00:57:43.870 --> 00:57:46.270 align:middle line:84% DIEDRE TOOLE: Most of it is synthesized 00:57:46.270 --> 00:57:47.710 align:middle line:90% within the atmosphere. 00:57:47.710 --> 00:57:50.270 align:middle line:84% The ventilation of it is very small, 00:57:50.270 --> 00:57:51.753 align:middle line:84% or is considered to be very small. 00:57:51.753 --> 00:57:53.670 align:middle line:84% I don't know if someone's measured it directly 00:57:53.670 --> 00:57:55.350 align:middle line:90% with flux measurements. 00:57:55.350 --> 00:57:58.070 align:middle line:90% 00:57:58.070 --> 00:57:59.870 align:middle line:84% I mean, there's other compounds, too, 00:57:59.870 --> 00:58:07.070 align:middle line:84% that come from deeper sources, and so on. 00:58:07.070 --> 00:58:08.270 align:middle line:90% OK. 00:58:08.270 --> 00:58:12.110 align:middle line:84% Another really important type of aerosol 00:58:12.110 --> 00:58:14.630 align:middle line:84% that we see in the troposphere is what's 00:58:14.630 --> 00:58:18.830 align:middle line:90% known as a mineral aerosol. 00:58:18.830 --> 00:58:22.150 align:middle line:84% Kind of what motivated people to start looking at this work 00:58:22.150 --> 00:58:22.710 align:middle line:90% is that-- 00:58:22.710 --> 00:58:26.320 align:middle line:84% I think you guys are going to get to this later-- 00:58:26.320 --> 00:58:31.000 align:middle line:84% is that there's huge areas of the world, the world's oceans, 00:58:31.000 --> 00:58:34.680 align:middle line:84% like the equatorial Pacific, the subarctic Pacific, the Southern 00:58:34.680 --> 00:58:38.240 align:middle line:84% Ocean, where concentrations of the macronutrients, 00:58:38.240 --> 00:58:40.760 align:middle line:84% like nitrate and phosphate, they're high year 00:58:40.760 --> 00:58:44.415 align:middle line:84% round, but we really have a low standing stock of phytoplankton. 00:58:44.415 --> 00:58:45.540 align:middle line:90% I'll just leave it at that. 00:58:45.540 --> 00:58:46.998 align:middle line:84% We're going to talk about it later. 00:58:46.998 --> 00:58:50.080 align:middle line:84% But these areas have been deemed these high nitrate, 00:58:50.080 --> 00:58:52.960 align:middle line:90% low chlorophyll HNLC regions. 00:58:52.960 --> 00:58:54.753 align:middle line:84% And so people, for a long time, we're 00:58:54.753 --> 00:58:57.420 align:middle line:84% trying to figure out, why isn't the phytoplankton growing there? 00:58:57.420 --> 00:59:00.940 align:middle line:84% They seemingly have the nutrients that they need. 00:59:00.940 --> 00:59:02.100 align:middle line:90% They should be happy. 00:59:02.100 --> 00:59:05.400 align:middle line:84% But primary production and standing stocks were still low. 00:59:05.400 --> 00:59:10.600 align:middle line:84% And in 1988, they initiated this, put forth this hypothesis 00:59:10.600 --> 00:59:12.920 align:middle line:84% that maybe it was a micronutrient limitation 00:59:12.920 --> 00:59:14.200 align:middle line:90% in iron. 00:59:14.200 --> 00:59:17.640 align:middle line:90% And that spurred a lot of-- hmm? 00:59:17.640 --> 00:59:19.880 align:middle line:84% AUDIENCE: Well, Riley said that in the '60s, too. 00:59:19.880 --> 00:59:22.930 align:middle line:84% DIEDRE TOOLE: Well-- OK, this is who's generally given credit 00:59:22.930 --> 00:59:23.830 align:middle line:90% for-- 00:59:23.830 --> 00:59:25.990 align:middle line:84% [LAUGHS] I don't know if it's fair credit, 00:59:25.990 --> 00:59:28.450 align:middle line:90% but that's another discussion. 00:59:28.450 --> 00:59:31.522 align:middle line:84% So a lot of people started looking at ion, 00:59:31.522 --> 00:59:33.230 align:middle line:84% trying to figure out where ion came from. 00:59:33.230 --> 00:59:33.910 align:middle line:90% What are its sources? 00:59:33.910 --> 00:59:34.710 align:middle line:90% What are its sinks? 00:59:34.710 --> 00:59:36.610 align:middle line:90% How is it processed? 00:59:36.610 --> 00:59:40.350 align:middle line:84% And there's been a lot of work on it, 00:59:40.350 --> 00:59:46.970 align:middle line:84% but one of the things that people have come upon 00:59:46.970 --> 00:59:51.410 align:middle line:84% is that the inputs of new iron to the surface waters, 00:59:51.410 --> 00:59:54.170 align:middle line:84% especially in open-ocean regions away from land, 00:59:54.170 --> 00:59:56.890 align:middle line:84% it's dominated by the atmospheric deposition 00:59:56.890 --> 01:00:01.610 align:middle line:84% of soluble ion in these aerosols through wet and dry deposition. 01:00:01.610 --> 01:00:07.410 align:middle line:84% And so if you want to look at a budget-- this is recently 01:00:07.410 --> 01:00:13.370 align:middle line:84% published in Science-- in terms of open ocean-dissolved iron, 01:00:13.370 --> 01:00:16.530 align:middle line:84% you have a lot of sources that just say they won't make it 01:00:16.530 --> 01:00:17.430 align:middle line:90% to the open ocean. 01:00:17.430 --> 01:00:20.947 align:middle line:84% I mean, a lot of the erosional processes from land, 01:00:20.947 --> 01:00:22.530 align:middle line:84% it's trapped on the continental shelf, 01:00:22.530 --> 01:00:24.238 align:middle line:84% and it doesn't make it to the open ocean. 01:00:24.238 --> 01:00:27.490 align:middle line:84% So this particulate iron from fluvial systems, 01:00:27.490 --> 01:00:29.330 align:middle line:84% glacial sediments and coastal erosion, 01:00:29.330 --> 01:00:33.070 align:middle line:84% I don't think those are relevant for open-ocean systems. 01:00:33.070 --> 01:00:36.110 align:middle line:84% But some of the more relevant pathways are 01:00:36.110 --> 01:00:39.450 align:middle line:84% the fluvial-dissolved iron-- though that's very low-- 01:00:39.450 --> 01:00:42.930 align:middle line:84% is in this atmospheric contribution. 01:00:42.930 --> 01:00:47.060 align:middle line:84% These are deeper contributions, so deep ocean contribution. 01:00:47.060 --> 01:00:48.310 align:middle line:90% And so you can see obviously-- 01:00:48.310 --> 01:00:51.910 align:middle line:84% I mean, the potential sources are very small, 01:00:51.910 --> 01:00:56.950 align:middle line:84% and it's pretty much atmospheric input. 01:00:56.950 --> 01:01:01.230 align:middle line:84% The one thing about iron is that, depending on its oxidation 01:01:01.230 --> 01:01:04.790 align:middle line:84% state, it depends on its bioavailability. 01:01:04.790 --> 01:01:09.870 align:middle line:84% I mean, primarily it's in these two forms, iron-3 versus iron-2. 01:01:09.870 --> 01:01:14.510 align:middle line:84% And when a particle from fluvial, 01:01:14.510 --> 01:01:17.230 align:middle line:84% from however it's transported to the ocean, 01:01:17.230 --> 01:01:21.760 align:middle line:84% iron is not really soluble under oxic conditions. 01:01:21.760 --> 01:01:25.020 align:middle line:84% So what happens is it quickly changes state. 01:01:25.020 --> 01:01:27.320 align:middle line:84% It has a very short half life, if you want 01:01:27.320 --> 01:01:30.640 align:middle line:90% to think about it in terms of-- 01:01:30.640 --> 01:01:34.720 align:middle line:84% when a particle of iron hits the surface of the ocean, 01:01:34.720 --> 01:01:36.460 align:middle line:84% it's this very quick competition, 01:01:36.460 --> 01:01:41.840 align:middle line:84% whether it's going to be taken up really rapidly by biology, 01:01:41.840 --> 01:01:45.040 align:middle line:84% whether it's going to become particulate form adsorbed 01:01:45.040 --> 01:01:49.520 align:middle line:84% to a particle, or whether it's going to do some of complexation 01:01:49.520 --> 01:01:52.000 align:middle line:90% with organic material. 01:01:52.000 --> 01:01:57.440 align:middle line:84% And so it's in this way that iron in the ocean 01:01:57.440 --> 01:02:01.080 align:middle line:84% has a very nutrient-like distribution. 01:02:01.080 --> 01:02:03.520 align:middle line:84% This is data compiled by Dave Carl. 01:02:03.520 --> 01:02:06.940 align:middle line:84% And this is just depth over the upper 4,000 meters, 01:02:06.940 --> 01:02:10.400 align:middle line:84% and then dissolved iron concentration ranging from 0 01:02:10.400 --> 01:02:13.080 align:middle line:90% to about 1.5 picomoles. 01:02:13.080 --> 01:02:16.420 align:middle line:84% And so what you can see is that iron is-- 01:02:16.420 --> 01:02:16.920 align:middle line:90% hmm? 01:02:16.920 --> 01:02:18.730 align:middle line:90% AUDIENCE: [INAUDIBLE] 01:02:18.730 --> 01:02:20.250 align:middle line:90% DIEDRE TOOLE: Ion is a-- 01:02:20.250 --> 01:02:23.010 align:middle line:84% it exists at very low subnanomolar concentrations 01:02:23.010 --> 01:02:24.370 align:middle line:90% in the surface waters. 01:02:24.370 --> 01:02:28.850 align:middle line:84% It's usually about 0.2, 0.1 in the surface, 01:02:28.850 --> 01:02:31.530 align:middle line:84% and it becomes more soluble with depth 01:02:31.530 --> 01:02:33.650 align:middle line:84% as a function of temperature, but also 01:02:33.650 --> 01:02:37.570 align:middle line:84% as a function of those organic ligands, which can complex it. 01:02:37.570 --> 01:02:44.150 align:middle line:84% But like I said, it's extremely insoluble in oceanic waters, 01:02:44.150 --> 01:02:47.090 align:middle line:84% so the bioavailability of ion is controlled by the presence 01:02:47.090 --> 01:02:50.850 align:middle line:90% of the organic ligands. 01:02:50.850 --> 01:02:53.810 align:middle line:84% And so if you're sitting out in the middle of one 01:02:53.810 --> 01:02:57.170 align:middle line:84% of the subtropical gyres, pretty much from the atmosphere 01:02:57.170 --> 01:03:02.410 align:middle line:84% is the only way you're going to get your iron. 01:03:02.410 --> 01:03:11.010 align:middle line:84% And what I have here is a map of estimates of dust flux. 01:03:11.010 --> 01:03:13.512 align:middle line:84% And one thing that's really important to remember-- 01:03:13.512 --> 01:03:14.970 align:middle line:84% we'll talk about this in a second-- 01:03:14.970 --> 01:03:20.780 align:middle line:84% is that dust is not necessarily equate to iron. 01:03:20.780 --> 01:03:23.060 align:middle line:84% The iron comes from the dust, but there 01:03:23.060 --> 01:03:25.140 align:middle line:84% are different reactions in the atmosphere that 01:03:25.140 --> 01:03:27.620 align:middle line:84% will affect its solubility and affect 01:03:27.620 --> 01:03:30.365 align:middle line:90% its delivery to the ocean. 01:03:30.365 --> 01:03:31.740 align:middle line:84% So as you can see from this, it's 01:03:31.740 --> 01:03:34.940 align:middle line:84% fairly obvious there are definite point 01:03:34.940 --> 01:03:37.260 align:middle line:90% sources for the dust. 01:03:37.260 --> 01:03:41.880 align:middle line:84% That's Northern Africa, Southern, Southern Africa, 01:03:41.880 --> 01:03:45.140 align:middle line:84% Australia, the hyperarid regions. 01:03:45.140 --> 01:03:50.020 align:middle line:84% And the amount of dust that can get entrained in the atmosphere 01:03:50.020 --> 01:03:54.900 align:middle line:84% is a function of a lot of geomorphological features, 01:03:54.900 --> 01:03:58.820 align:middle line:84% just the amount of dust there, the topography, 01:03:58.820 --> 01:04:04.900 align:middle line:84% how arid it is, how erosion capable it is, wind speed. 01:04:04.900 --> 01:04:07.780 align:middle line:84% And then once these dust particles 01:04:07.780 --> 01:04:12.420 align:middle line:84% are entrained into the atmosphere, how long they stay 01:04:12.420 --> 01:04:15.310 align:middle line:84% in the atmosphere depends on a lot of processes, 01:04:15.310 --> 01:04:16.750 align:middle line:90% like precipitation. 01:04:16.750 --> 01:04:19.630 align:middle line:84% The bigger particles obviously fall out first, 01:04:19.630 --> 01:04:23.630 align:middle line:84% where smaller particles can be transported longer. 01:04:23.630 --> 01:04:29.510 align:middle line:84% Just transport processes-- amount of water vapor in the air 01:04:29.510 --> 01:04:32.750 align:middle line:90% also matters a lot. 01:04:32.750 --> 01:04:39.670 align:middle line:84% So it's also interesting to note that it's very dependent 01:04:39.670 --> 01:04:42.030 align:middle line:84% not just spatially but seasonally, 01:04:42.030 --> 01:04:44.510 align:middle line:84% like I mentioned, the amount of rainfall, 01:04:44.510 --> 01:04:46.670 align:middle line:84% and where that rain is happening is 01:04:46.670 --> 01:04:51.190 align:middle line:84% going to determine how this iron is delivered to the ocean. 01:04:51.190 --> 01:04:56.990 align:middle line:84% And on longer scales, glacier, interglacial variability 01:04:56.990 --> 01:04:59.270 align:middle line:84% determines the amount of iron, in terms 01:04:59.270 --> 01:05:03.310 align:middle line:84% of the dryness of the planet, the amount of water that's 01:05:03.310 --> 01:05:09.390 align:middle line:84% tied up in the ice caps, the height of the sea surface. 01:05:09.390 --> 01:05:13.130 align:middle line:84% And it's very episodic, based on wind speeds. 01:05:13.130 --> 01:05:17.190 align:middle line:84% So the one thing that we really need to consider, 01:05:17.190 --> 01:05:20.250 align:middle line:84% though, is once we have these dust particles blowing around 01:05:20.250 --> 01:05:23.890 align:middle line:84% and landing on the ocean surface is how much that actually 01:05:23.890 --> 01:05:25.810 align:middle line:84% is iron, and how much of that is actually 01:05:25.810 --> 01:05:28.730 align:middle line:84% available to phytoplankton for primary productivity 01:05:28.730 --> 01:05:30.255 align:middle line:90% and for their other functions. 01:05:30.255 --> 01:05:32.130 align:middle line:84% Iron is involved in a lot of enzyme functions 01:05:32.130 --> 01:05:35.930 align:middle line:84% that are pretty critical to phytoplankton processes. 01:05:35.930 --> 01:05:38.130 align:middle line:84% And generally, what a lot of people 01:05:38.130 --> 01:05:40.630 align:middle line:84% consider is that the Earth's crust, 01:05:40.630 --> 01:05:44.650 align:middle line:84% the soil particles are about 3.5% iron. 01:05:44.650 --> 01:05:50.410 align:middle line:84% And so that's a good average, of the particle 3.5% of it is iron. 01:05:50.410 --> 01:05:52.130 align:middle line:84% But there's a lot of reactions that 01:05:52.130 --> 01:05:55.970 align:middle line:84% happen in aerosols that can potentially increase 01:05:55.970 --> 01:05:58.330 align:middle line:90% the solubility of that iron. 01:05:58.330 --> 01:06:03.450 align:middle line:84% And some of that has to do with the acidity of the aerosol. 01:06:03.450 --> 01:06:07.870 align:middle line:84% And so when they hit the surface of the ocean, 01:06:07.870 --> 01:06:12.800 align:middle line:84% they might have a much higher solubility ability than the 3.5% 01:06:12.800 --> 01:06:17.460 align:middle line:84% or even down as 1% some people use as estimates. 01:06:17.460 --> 01:06:20.500 align:middle line:84% But that's a very important way in which the atmosphere delivers 01:06:20.500 --> 01:06:24.500 align:middle line:84% a key micronutrient to areas of the ocean that would pretty much 01:06:24.500 --> 01:06:29.580 align:middle line:90% be starved of iron otherwise. 01:06:29.580 --> 01:06:33.460 align:middle line:84% And these are just some examples of different ways 01:06:33.460 --> 01:06:37.140 align:middle line:84% you can estimate the amount of iron and get at things. 01:06:37.140 --> 01:06:41.340 align:middle line:84% One is a SeaWiFS true color image from February 28 01:06:41.340 --> 01:06:43.020 align:middle line:90% of the year 2000. 01:06:43.020 --> 01:06:45.780 align:middle line:84% And you can see, this is the coast of northern Africa. 01:06:45.780 --> 01:06:46.880 align:middle line:90% This is Spain. 01:06:46.880 --> 01:06:50.940 align:middle line:84% And you can just see these vast plumes of dust particles being 01:06:50.940 --> 01:06:52.900 align:middle line:90% blown across the continent. 01:06:52.900 --> 01:06:55.100 align:middle line:84% And so they have satellite algorithms, 01:06:55.100 --> 01:06:59.293 align:middle line:84% looking at aerosol optical depth to estimate the amount of dust. 01:06:59.293 --> 01:07:00.960 align:middle line:84% There's also what some people have done, 01:07:00.960 --> 01:07:02.760 align:middle line:84% which is just a much more direct way, 01:07:02.760 --> 01:07:06.580 align:middle line:84% is they've just taken rainwater from areas 01:07:06.580 --> 01:07:10.470 align:middle line:84% where they expect a lot of dust to be delivered and filtered it. 01:07:10.470 --> 01:07:13.625 align:middle line:84% And so this is one that we did in July of 2004. 01:07:13.625 --> 01:07:15.250 align:middle line:84% And it's kind of a hard picture to see. 01:07:15.250 --> 01:07:18.957 align:middle line:84% But you could see a lot of dust particles coming from the rain. 01:07:18.957 --> 01:07:21.290 align:middle line:84% And analysis showed that there's a lot of iron in those. 01:07:21.290 --> 01:07:26.270 align:middle line:90% 01:07:26.270 --> 01:07:28.350 align:middle line:84% Just to touch on another way in which 01:07:28.350 --> 01:07:30.910 align:middle line:84% the atmosphere and the ocean are directly coupled 01:07:30.910 --> 01:07:33.150 align:middle line:84% and which affects a lot of what we do, 01:07:33.150 --> 01:07:36.870 align:middle line:84% is nitrogen deposition in the form of acid rain 01:07:36.870 --> 01:07:38.830 align:middle line:90% on the surface of the ocean. 01:07:38.830 --> 01:07:43.150 align:middle line:84% And one of the biggest sources of nitrogen to the atmosphere 01:07:43.150 --> 01:07:45.930 align:middle line:90% is nitrous oxide from the ocean. 01:07:45.930 --> 01:07:47.790 align:middle line:90% And it contributes about-- 01:07:47.790 --> 01:07:50.430 align:middle line:84% Generally, this nitrous oxide is formed 01:07:50.430 --> 01:07:53.030 align:middle line:84% in nitrification processes, a little bit associated 01:07:53.030 --> 01:07:55.070 align:middle line:90% with denitrification. 01:07:55.070 --> 01:07:59.310 align:middle line:84% So you're going to find these produced at deeper depths. 01:07:59.310 --> 01:08:03.590 align:middle line:84% And so when these waters are upwelled or in deep convective 01:08:03.590 --> 01:08:06.550 align:middle line:84% areas, you're going to have spurts of nitrous oxide being 01:08:06.550 --> 01:08:09.360 align:middle line:90% injected into the atmosphere. 01:08:09.360 --> 01:08:13.720 align:middle line:84% We also have lots of sources of the higher nitrogen oxides 01:08:13.720 --> 01:08:15.920 align:middle line:90% from anthropogenic sources. 01:08:15.920 --> 01:08:17.819 align:middle line:84% And when they talk about anthropogenic a lot, 01:08:17.819 --> 01:08:21.920 align:middle line:84% they talk about NOX, which is the sum of nitric oxide 01:08:21.920 --> 01:08:24.000 align:middle line:90% and nitrogen dioxide. 01:08:24.000 --> 01:08:25.960 align:middle line:84% And a lot of these sources of nitrogen 01:08:25.960 --> 01:08:31.080 align:middle line:84% comes from fossil fuels, biomass burning, and fertilizer. 01:08:31.080 --> 01:08:33.380 align:middle line:84% There's also some interesting natural processes. 01:08:33.380 --> 01:08:38.080 align:middle line:84% Like lightning, for example, can form a lot of these oxides. 01:08:38.080 --> 01:08:47.520 align:middle line:84% And just considering the NOX chemistry in the stratosphere 01:08:47.520 --> 01:08:52.000 align:middle line:84% is, it's another way to destroy ozone. 01:08:52.000 --> 01:08:55.960 align:middle line:84% So you have nitric oxide plus your ozone leads 01:08:55.960 --> 01:08:59.880 align:middle line:84% to your nitrogen dioxide and oxygen. 01:08:59.880 --> 01:09:04.359 align:middle line:84% And then when you combine this with an OH radical, 01:09:04.359 --> 01:09:07.410 align:middle line:90% you yield nitric acid. 01:09:07.410 --> 01:09:12.410 align:middle line:84% So this is a way for anthropogenic and natural inputs 01:09:12.410 --> 01:09:17.290 align:middle line:84% to load up essentially the acidity of a lot of the water 01:09:17.290 --> 01:09:20.569 align:middle line:90% particles in these regions. 01:09:20.569 --> 01:09:24.149 align:middle line:84% And this nitric acid is highly soluble in droplets. 01:09:24.149 --> 01:09:29.029 align:middle line:84% So whenever it has any encounter with condensed-phase water, 01:09:29.029 --> 01:09:30.870 align:middle line:90% it dissolves in there. 01:09:30.870 --> 01:09:34.170 align:middle line:84% So it's very subject to wet deposition. 01:09:34.170 --> 01:09:37.609 align:middle line:84% And just kind of an interesting side note, 01:09:37.609 --> 01:09:39.210 align:middle line:84% in terms of the ocean's effect, is 01:09:39.210 --> 01:09:41.609 align:middle line:84% that the photolysis of nitrogen dioxide 01:09:41.609 --> 01:09:43.370 align:middle line:84% is the only known way of producing 01:09:43.370 --> 01:09:46.410 align:middle line:90% ozone in the troposphere. 01:09:46.410 --> 01:09:49.024 align:middle line:84% There are injections of anthropogenically-produced 01:09:49.024 --> 01:09:51.649 align:middle line:84% ozone, but that's the only known way of chemically producing it 01:09:51.649 --> 01:09:54.090 align:middle line:90% in the troposphere. 01:09:54.090 --> 01:09:58.510 align:middle line:84% And so what happens to this nitric acid once it forms? 01:09:58.510 --> 01:10:01.890 align:middle line:84% We've increased the acidity of the atmosphere. 01:10:01.890 --> 01:10:04.710 align:middle line:84% And you have all these wet deposition processes. 01:10:04.710 --> 01:10:06.310 align:middle line:90% Eventually, it rains out. 01:10:06.310 --> 01:10:08.310 align:middle line:84% Your particles get big enough, and they rain out 01:10:08.310 --> 01:10:09.910 align:middle line:90% of your clouds. 01:10:09.910 --> 01:10:16.270 align:middle line:84% So what I've shown here is a map of estimated distributions of pH 01:10:16.270 --> 01:10:19.350 align:middle line:90% of rain particles globally. 01:10:19.350 --> 01:10:21.550 align:middle line:84% And one thing we should know from the beginning 01:10:21.550 --> 01:10:24.070 align:middle line:84% is that natural precipitation rain 01:10:24.070 --> 01:10:27.670 align:middle line:84% is slightly acidic because of CO2 and carbonic acid 01:10:27.670 --> 01:10:30.310 align:middle line:84% dissolving in it from the atmosphere. 01:10:30.310 --> 01:10:35.510 align:middle line:84% So the common definition is that a pH of less than 5.6 01:10:35.510 --> 01:10:38.430 align:middle line:90% is considered acid rain. 01:10:38.430 --> 01:10:42.070 align:middle line:84% And so we can see definite point sources, 01:10:42.070 --> 01:10:46.230 align:middle line:84% where the pH is as low as four, associated with anthropogenics. 01:10:46.230 --> 01:10:50.590 align:middle line:84% But you can also see large areas of the open ocean, where 01:10:50.590 --> 01:10:53.710 align:middle line:90% the pH is relatively low also. 01:10:53.710 --> 01:10:56.282 align:middle line:84% And this is generally associated with nitric acid. 01:10:56.282 --> 01:10:57.990 align:middle line:84% And I didn't go into the details of this. 01:10:57.990 --> 01:11:02.840 align:middle line:84% But this sulfuric acid from the sulfur cycle, they 01:11:02.840 --> 01:11:04.800 align:middle line:90% also will decrease the pH. 01:11:04.800 --> 01:11:08.120 align:middle line:84% And besides decreasing the pH, they also 01:11:08.120 --> 01:11:10.700 align:middle line:84% deliver nitrogen and sulfur to the surface ocean. 01:11:10.700 --> 01:11:13.960 align:middle line:90% 01:11:13.960 --> 01:11:16.440 align:middle line:84% One just the last thing that I wanted 01:11:16.440 --> 01:11:20.420 align:middle line:84% to mention really briefly, just so you know it's there. 01:11:20.420 --> 01:11:24.520 align:middle line:84% I mean, if you remember talking about the ozone 01:11:24.520 --> 01:11:27.680 align:middle line:84% hole and the ozone loss, we talked a lot about chlorine. 01:11:27.680 --> 01:11:29.720 align:middle line:84% So halogen chemistry is actually very 01:11:29.720 --> 01:11:31.880 align:middle line:84% important in the environment in terms 01:11:31.880 --> 01:11:36.200 align:middle line:84% of catalytic-destruction processes. 01:11:36.200 --> 01:11:41.200 align:middle line:84% But there's also a lot of organic biogenic sources. 01:11:41.200 --> 01:11:43.240 align:middle line:84% Specifically in the ocean, there's 01:11:43.240 --> 01:11:46.740 align:middle line:84% what's known as the methyl halides, which is chlorine, 01:11:46.740 --> 01:11:49.960 align:middle line:90% bromine, and iodine forms. 01:11:49.960 --> 01:11:53.400 align:middle line:84% And these have really long lifetimes, greater than-- 01:11:53.400 --> 01:11:56.720 align:middle line:84% about a year, with respect to the OH radical. 01:11:56.720 --> 01:11:58.520 align:middle line:84% So they can reach the stratosphere, 01:11:58.520 --> 01:12:01.890 align:middle line:84% and they can function and as a catalytic species 01:12:01.890 --> 01:12:03.110 align:middle line:90% in that ozone destruction. 01:12:03.110 --> 01:12:05.510 align:middle line:84% Exactly how the CFCs from anthropogenics can do it. 01:12:05.510 --> 01:12:07.010 align:middle line:84% These can get up in the stratosphere 01:12:07.010 --> 01:12:09.610 align:middle line:90% and do the same thing. 01:12:09.610 --> 01:12:11.930 align:middle line:84% And another really important source 01:12:11.930 --> 01:12:13.978 align:middle line:84% of halogens that I just want you to be aware of, 01:12:13.978 --> 01:12:15.770 align:middle line:84% I didn't want to talk about too much today, 01:12:15.770 --> 01:12:18.890 align:middle line:90% is sea-salt particles. 01:12:18.890 --> 01:12:21.250 align:middle line:84% This is an inorganic halogen, but there's a way 01:12:21.250 --> 01:12:24.170 align:middle line:84% that these halogens can be activated. 01:12:24.170 --> 01:12:27.890 align:middle line:84% And essentially, the way this works is you take your sodium 01:12:27.890 --> 01:12:31.070 align:middle line:84% chloride, which is essentially your sea-salt particle, 01:12:31.070 --> 01:12:33.050 align:middle line:84% has been injected to the air and either dried 01:12:33.050 --> 01:12:35.570 align:middle line:84% or still in a condensed phase, and then you 01:12:35.570 --> 01:12:39.430 align:middle line:84% react it with one of your chlorine-reservoir species. 01:12:39.430 --> 01:12:40.930 align:middle line:84% These are the same reservoir species 01:12:40.930 --> 01:12:43.610 align:middle line:84% that we talked about in terms of the ozone hole. 01:12:43.610 --> 01:12:49.210 align:middle line:84% And that liberates chlorine gas and then sodium nitrate. 01:12:49.210 --> 01:12:52.410 align:middle line:84% So what you have then is your chlorine gas, 01:12:52.410 --> 01:12:55.370 align:middle line:84% which can be photolyzed into chlorine atoms. 01:12:55.370 --> 01:12:59.660 align:middle line:84% And you can start the same exact catalytic-destruction cycle 01:12:59.660 --> 01:13:03.180 align:middle line:84% of ozone that happens in the polar ozone hole. 01:13:03.180 --> 01:13:08.900 align:middle line:84% So sea-salt particles are also a very important removal pathway 01:13:08.900 --> 01:13:11.860 align:middle line:84% of nitrogen oxides and some of the acidity, some 01:13:11.860 --> 01:13:13.820 align:middle line:84% of the acid rain causing compounds 01:13:13.820 --> 01:13:15.540 align:middle line:90% we were just talking about. 01:13:15.540 --> 01:13:19.100 align:middle line:84% And the way they work is you take your nitric acid 01:13:19.100 --> 01:13:23.340 align:middle line:84% and that if it comes across a sea-salt particle 01:13:23.340 --> 01:13:26.620 align:middle line:84% can break down into sodium nitrate and HCl, 01:13:26.620 --> 01:13:29.800 align:middle line:84% and then that goes from there and has a bunch of reactions. 01:13:29.800 --> 01:13:32.300 align:middle line:84% But essentially, these sea-salt particles 01:13:32.300 --> 01:13:35.180 align:middle line:84% produce a lot of surfaces where you can change 01:13:35.180 --> 01:13:37.820 align:middle line:90% the acidity of the atmosphere. 01:13:37.820 --> 01:13:39.820 align:middle line:84% And so they affect the NOX partitioning 01:13:39.820 --> 01:13:41.480 align:middle line:90% in the ozone chemistry overall. 01:13:41.480 --> 01:13:44.960 align:middle line:84% And there's actually-- in terms of overall mass, 01:13:44.960 --> 01:13:48.420 align:middle line:84% the flux of sea salt particles to the aerosol load 01:13:48.420 --> 01:13:51.460 align:middle line:90% is pretty enormous. 01:13:51.460 --> 01:13:56.900 align:middle line:84% So just to summarize this tour we did today of the ocean 01:13:56.900 --> 01:14:00.510 align:middle line:84% and the atmosphere is that atmospheric gases and aerosols 01:14:00.510 --> 01:14:04.750 align:middle line:84% impact the global-radiation budget and the heat budget. 01:14:04.750 --> 01:14:08.470 align:middle line:84% The trace constituents really dominate these effects. 01:14:08.470 --> 01:14:11.250 align:middle line:84% The reaction pathways and the feedback mechanisms, 01:14:11.250 --> 01:14:12.290 align:middle line:90% they're often complex. 01:14:12.290 --> 01:14:15.750 align:middle line:84% They're interrelated and have these cyclical mechanisms, 01:14:15.750 --> 01:14:18.870 align:middle line:84% making climate-change estimates difficult. 01:14:18.870 --> 01:14:21.395 align:middle line:84% But many of these biogeochemical cycles 01:14:21.395 --> 01:14:23.270 align:middle line:84% are really important to us, as oceanographers 01:14:23.270 --> 01:14:25.830 align:middle line:84% and marine chemists, because they deliver key substances 01:14:25.830 --> 01:14:29.510 align:middle line:84% to the ocean, like iron and nitrogen and sulfur and vice 01:14:29.510 --> 01:14:30.130 align:middle line:90% versa. 01:14:30.130 --> 01:14:33.390 align:middle line:84% The ocean can deliver them to the atmosphere. 01:14:33.390 --> 01:14:35.290 align:middle line:90% So that's it. 01:14:35.290 --> 01:14:38.070 align:middle line:90% 01:14:38.070 --> 01:14:38.930 align:middle line:90% Any questions? 01:14:38.930 --> 01:14:43.910 align:middle line:90% 01:14:43.910 --> 01:14:44.590 align:middle line:90% AUDIENCE: Hi. 01:14:44.590 --> 01:14:49.150 align:middle line:84% When you're talking about the iron, so when they do, like, 01:14:49.150 --> 01:14:53.007 align:middle line:84% the iron experiments, what form of iron are they adding? 01:14:53.007 --> 01:14:55.590 align:middle line:84% Are they just-- I mean, they're clearly not just dropping them 01:14:55.590 --> 01:14:56.890 align:middle line:90% in, like, scrap metal. 01:14:56.890 --> 01:14:59.070 align:middle line:90% [LAUGHTER] 01:14:59.070 --> 01:14:59.192 align:middle line:90% 01:14:59.192 --> 01:15:00.650 align:middle line:84% DIEDRE TOOLE: Throw an anchor over. 01:15:00.650 --> 01:15:02.110 align:middle line:90% I mean, it really depends. 01:15:02.110 --> 01:15:03.930 align:middle line:90% I mean, the iron-- 01:15:03.930 --> 01:15:06.250 align:middle line:84% I don't know actually what the specific chemical 01:15:06.250 --> 01:15:07.830 align:middle line:90% that they put in-- 01:15:07.830 --> 01:15:10.130 align:middle line:84% AUDIENCE: Could just be an iron chloride. 01:15:10.130 --> 01:15:11.930 align:middle line:90% DIEDRE TOOLE: I imagine so. 01:15:11.930 --> 01:15:16.130 align:middle line:84% I mean, they obviously try to put it in in a more soluble form 01:15:16.130 --> 01:15:20.610 align:middle line:84% and hope that it retains its solubility 01:15:20.610 --> 01:15:21.850 align:middle line:90% for as long as possible. 01:15:21.850 --> 01:15:25.290 align:middle line:84% Oftentimes, that's why they do a second edition and sometimes 01:15:25.290 --> 01:15:28.970 align:middle line:84% a third injection because it absorbs 01:15:28.970 --> 01:15:31.390 align:middle line:84% some particles and changes its oxidation state. 01:15:31.390 --> 01:15:34.410 align:middle line:90% 01:15:34.410 --> 01:15:38.563 align:middle line:84% AUDIENCE: I can email you the answer to that question. 01:15:38.563 --> 01:15:39.730 align:middle line:90% AUDIENCE: There was a story. 01:15:39.730 --> 01:15:42.850 align:middle line:84% I remember hearing about some guy who was trying to-- 01:15:42.850 --> 01:15:46.650 align:middle line:84% he was getting people to pay him to take, like, 01:15:46.650 --> 01:15:49.295 align:middle line:84% old pieces of scrap iron out and dump it in the ocean. 01:15:49.295 --> 01:15:50.170 align:middle line:90% DIEDRE TOOLE: Really? 01:15:50.170 --> 01:15:50.795 align:middle line:90% AUDIENCE: Yeah. 01:15:50.795 --> 01:15:53.570 align:middle line:84% He was saying it was going to fertilize the ocean and decrease 01:15:53.570 --> 01:15:56.180 align:middle line:90% increase CO2. 01:15:56.180 --> 01:15:56.865 align:middle line:90% [INAUDIBLE] 01:15:56.865 --> 01:15:58.240 align:middle line:84% DIEDRE TOOLE: That's interesting. 01:15:58.240 --> 01:15:59.740 align:middle line:84% We could get someone to pay him to do it. 01:15:59.740 --> 01:16:00.365 align:middle line:90% AUDIENCE: Yeah. 01:16:00.365 --> 01:16:02.640 align:middle line:90% [LAUGHTER] 01:16:02.640 --> 01:16:04.860 align:middle line:90% 01:16:04.860 --> 01:16:06.620 align:middle line:90% Oh, they can't hear us at all. 01:16:06.620 --> 01:16:09.120 align:middle line:84% AUDIENCE: Those stock compounds that you were talking about, 01:16:09.120 --> 01:16:10.837 align:middle line:84% the chlorine and nitrogen compounds-- 01:16:10.837 --> 01:16:12.420 align:middle line:84% DIEDRE TOOLE: The reservoir compounds. 01:16:12.420 --> 01:16:14.013 align:middle line:84% AUDIENCE: --where do those come from? 01:16:14.013 --> 01:16:15.180 align:middle line:90% DIEDRE TOOLE: They're just-- 01:16:15.180 --> 01:16:20.700 align:middle line:90% they ultimately start out as-- 01:16:20.700 --> 01:16:23.520 align:middle line:84% well, where do the original compounds in the atmosphere-- 01:16:23.520 --> 01:16:25.440 align:middle line:84% they're very long-lived compounds. 01:16:25.440 --> 01:16:31.620 align:middle line:84% They're regenerated each year through these reactions. 01:16:31.620 --> 01:16:34.160 align:middle line:84% I'm sure you can have formation of them if you have-- 01:16:34.160 --> 01:16:37.372 align:middle line:84% because you have a very slow mixing between the troposphere 01:16:37.372 --> 01:16:38.080 align:middle line:90% and stratosphere. 01:16:38.080 --> 01:16:40.120 align:middle line:84% You can get some of the halides mixed up. 01:16:40.120 --> 01:16:44.020 align:middle line:84% It's probably mostly started with the organic 01:16:44.020 --> 01:16:46.300 align:middle line:84% naturally occurring halides and sea salt, 01:16:46.300 --> 01:16:49.980 align:middle line:84% injecting the chlorine, and then those compounds forming. 01:16:49.980 --> 01:16:53.850 align:middle line:84% But they do regenerate themselves each year.