 I'm pleased to introduce our next speaker, Paul Falkowski. Paul is a board of governors professor of geological sciences in the Institute of Marine and Coastal Sciences in the Department of Earth and Planetary Sciences at Rutgers University. The title of his talk is Oceans as Natural Climate Solutions. Over to you, Paul. Thank you very much, and thank you all for inviting me. It's been a long time since I thought about this. I guess since the late 1970s, early 1980s, when the Department of Energy set up the first carbon dioxide office. And I was working at Brookhaven National Lab. And so I go back a long way with this problem, and I just want to think about this with you for a minute. When you think about the oceans, you have to think about geologic time scales. And the oceans, although they cover 71% of the Earth's surface, actually they covered significantly more of that over geologic time. And we don't know where the water came from, to be honest with you. It was imported almost certainly from chondritic meteorites. But that was the source of water, and we're the only planet in the entire solar system that has liquid water on its surface. And at four periods of Earth's history, that water was completely frozen, we think, over virtually the entire Earth's surface. And when it is frozen, there's no exchange of carbon dioxide or any other gas between the ocean, liquid ocean, beneath and the atmosphere above. Now if we take all that water and put it into a ball, that's the volume it would contain. So if you are teaching and you want to give some aspect of the volume of water compared to the diameter of the Earth, if the diameter of the Earth is one meter, the entire diameter of the Earth is one meter, the thickness of the water on the surface of the Earth would be equal to about two typewriter pages. That's it. So it's a very, very thin film of water, which is remarkable that it stayed on this planet for so long. It's been on the planet, we know, for at least 4.3 billion years. And it is no longer on Mars, it is no longer on Venus. I just want to make a point that for the, from 4.3 billion years until 430 million years ago, the oceans were the source and sink of natural CO2 from volcanoes. There were no terrestrial land plants until about 430 million years ago. So they're relatively recent invention. Now let's just take a look at what's in the water. Water dissolves ions from rocks. And so we have obviously the main cation is sodium and then followed by magnesium, which is in order of magnitude less. And then calcium, potassium and strontium. And then we have the anions. We have chloride is obviously the major one that comes from actually volcanic gas emissions, sulfate as well. And then bicarbonate is the third largest one. Now the calcium and magnesium, and to some extent the boron, they act as what we call buffers and contribute to what's called alkalinity. So the bicarbonate in the ocean is a sink, ultimately for atmospheric CO2 from volcanic outgassing. Now in pH of sea water, the normal pH of sea water, and it's been this way for hundreds and hundreds and hundreds of millions of years, if not billions of years. The pH is about 8.2, roughly between 7.9 and 8.5. About 95% of the inorganic carbon in the ocean is in the form of bicarbonate anion. Only about 5% to 6% is in the form of carbon dioxide per se and a smaller amount or a larger amount, depending on the pH is in the form of carbonate. Now on geologic time scales, the ocean transfers inorganic carbon in a form of CO2 to the terrestrial biosphere via the atmosphere. So bicarbonate is obviously a salt, an ion, it's not volatile. So it has to be converted to CO2. And the atmosphere is really, if you think about it, a hallway between two large rooms, between a terrestrial biosphere and the ocean itself. And we can see this on geologic time scales, how this works. So this is an example of an ice core record from the Antarctic. And this goes back about 800,000 years. We go back roughly to the end of the ice core record is going to be about one million years. And you can see several things here. First, that there's a cyclicity of about 100,000 years in carbon dioxide, and that's the upper blue line and temperature. And the bottom line of methane is a very interesting one. I'm not gonna talk about it unless there's a question about it, but it also cycles. Now the carbon dioxide cycle and the question of whether temperature led to carbon dioxide, or carbon dioxide led to temperature has been one that's been debated for a long time. I think most of the consensus is that carbon dioxide leaves the changes in the temperature, not the temperature changes the carbon dioxide. Now what's the 100,000 year cycle here? Now let's just talk about it for a second. So during interglacial time, carbon dioxide goes up to about between 260 and 280 ppm CO2. And that's measured from the gas bubbles in the ice cores. So we know that with relatively high accuracy. And it goes down during glacial times to about 180. So there's this cycle that is very natural on 100,000 year timescales. And that 100,000 year timescale has been the same for roughly the last three and a half million years. Before that it was a 40,000 year timescale. Now what causes this? We correlate this, we don't really understand it, but we correlate it with the Milankovic cycles. So the Milankovic cycles have three different systems in them, there's procession, which I show on the top, we're going from 23 and a half degrees off axis to a roughly 24, 24 and a half. And then we have the obliquity and then we have eccentricity. And when we put those three together, you can develop a synthetic curve. And it's obvious that the eccentricity is the main driver of the glacial interglacial system. Now we are in what would be the end of a interglacial period. And carbon dioxide should be, if all things were natural, staying the same for periods of a few thousand years and then going down. So where is the dissolved in organic carbon in the ocean? So the dissolved in organic carbon in the ocean is in the deep ocean. The surface ocean is lower than the deep ocean by about 250 to 400 ppm CO2, depending on where you are or dissolved in organic carbon micromoles. And there's the alkalinity curve on the right. I'm not gonna go into that for the moment, but the alkalinity curve is also depressed as you approach the surface. So why is that? Well, the carbon in the ocean can be pumped into the so-called into the deep ocean. There are two main pumps. One is the solubility pump where the atmospheric carbon dioxide can be dissolved and then go in through the thermocline as water sinks. Now, where does that happen? That primarily happens in cold waters in the Northern Hemisphere around Greenland. It can happen in the Southern Hemisphere in the Antarctic today. The second sink is called the biologic pump from Tyler Volk and Marty Hofford. And this sink is based on the fact that photosynthetic organisms, the phytoplankton in the surface waters, photosynthesize and sink into the deep ocean and decompose. And when they decompose, they release their nutrients and carbon dioxide. The decomposition is done by bacteria. And so that decomposition leads to this so-called biologic pump, which enriches the deep ocean by a few hundred ppm micromoles of CO2. And there's a little bit of calcite rock weathering, which I'm not gonna go into here. This is a major sink for volcanic carbon on geologic time scales. That is the major sink for. When we talk to a geologist and talk about a carbon cycle, they don't think about photosynthesis and respiration. They're thinking about volcanism and rock weathering. So in the steady state, which is on the time scales of decades in the ocean, and we have an ocean record for carbon dioxide that goes back to the Challenger Expedition in the later last part of the 19th century. We actually measured CO2 in during the Challenger Expedition. It was quite ingenious actually. And it was not as obviously as precise as it is today. We have a precise record of CO2 and nutrients in the ocean for about 70 years. Now, in the steady state, the dissolved inorganic carbon is driven by physics and chemistry, not biology. So that's totally in contrast to what Rob and Chris are talking about. This is where biology controls the terrestrial carbon sink and source. And I just wanna now talk about the role of the biologic pump because this has been misunderstood and mischaracterized for a long time. So this is an annual, many annual cycles from sea whiffs of the terrestrial and marine biosphere and green in the ocean is high biomass relatively and blue and red is very low, red is very, very low biomass. So the South Pacific Ocean is ultra oligotrophic. So where do these nutrients come from? These nutrients are coming from the seasonal change in the thermocline. So they're bringing nutrients from depth up to the surface and it occurs, for example, in the North Atlantic quite well. So you get these blooms in the spring. Now, let's imagine that we could change that mixing rate and just put a big egg beater in the ocean, if you will. Would it change the CO2 in the atmosphere by adding nutrients to the upper ocean? The answer is no. And that may be surprising because when you're doing that, you're bringing nitrate or phosphate up in the upper ocean, for example, stimulating productivity. You're also bringing up carbon dioxide from depth or dissolved in organic carbon from depth, which would become carbon dioxide in the surface. So there's no change in the steady state by just mixing the ocean. And so that has been an issue that was misunderstood, I think, by the biologists during the so-called JGOS program. And it's sometimes very confusing for geologists to understand why the biologists are doing these kinds of long-term experiments. Now, I just wanna talk about what controls the productivity of the ocean because it leads on to manipulation of the carbon in the ocean. So Alfred Redfield, who was a biologist, was in Plymouth, England, and he was shown the nitrate, new nitrate to phosphate ratios through the English channel. And he realized that the ratio was 16 to one by Adams. And then he looked at the ratio, which he didn't do any measurements, by the way. He looked at the ratio at that time of the plankton. And the plankton had a canonical, what's called canonical ratio of 106 to 16 to one. That became the Redfield ratio. So if it's not 106 to 16 to one, if it's, let's say, somebody tells you it's 100 to 15 to one, that's not the Redfield ratio. That's another stoichiometry. It exists, but the Redfield ratio canonically is 106 to 16 to one. Now, let's take a look at what limits productivity in the ocean. This has been going on now for 50, 60 years. So these are the three major ocean basins. And there's the 16 to one vertical line. So if everything was at 16 to one, you would see that vertical line for the nitrate to phosphate in the ocean. You don't, except in the North Atlantic. So everywhere in the Pacific and the Indian Ocean, for example, the line is less than 16 to one. So we have less nitrate than phosphate from the sinking flux. And you have less nitrate to phosphate from the sinking flux in the Pacific ocean. And it approaches the sinking flux in the Atlantic ocean. And it actually can exceed it. You can see those lines deviate to the high end in the Mediterranean, for example, which has an N to P ratio of 25 to 30 in some cases. So why? That's because when you sink nitrate biomass into the ocean, if it encounters low oxygen, it denitrifies. So the denitrification takes the nitrate out of the ocean and you're left with a deficit of nitrate. Now, let's imagine you could fill that somehow. Let's increase nitrogen fixation. If I could fill that and make that go to 16 to one, how much carbon dioxide would I take out of the atmosphere? So I did that thought experiment years ago and it was published in Nature. And the answer is about 35 to 40 PPM CO2. So it's not an incredibly large sink, but it's not insignificant. Now, there's another aspect of this which is misunderstood often by biologists. And it is that we can precipitate carbonate. So there's a lot of carbonates that precipitated, especially in the Atlantic Ocean, which is shallow enough to keep it in the sediments. When you precipitate inorganic carbon as carbonate, you actually release CO2 to the atmosphere. So that is not a solution for re-sequestering CO2 on time scales of decades, the centuries. Now, where's the organic carbon? So organic carbon is stored in shallow seas and along continental margins around the world. And that organic carbon is there for tens of thousands of years. In some cases, hundreds of thousands of years. And in some cases, when it becomes part of land biomass, millions of years. So we had a seaway that ran from Alberta down through to Mexico. And that seaway is a major reservoir of stored organic carbon in the form of oil and natural gas. And similarly, Oman and Saudi Arabia, those were all underwater at one point. And these are the major sinks of carbon on geologic time scales. And we're really smart animals. So we can extract in one year, one million years worth of deposition of that organic carbon. So we're one million times more efficient at taking it out of the ground than nature was in putting it into the ground in the form of fossil fuels. So can we monkey with the biological pump? The answer is yes. And the question is, should we? So let's take a look at how we could monkey with it and then before we get to the question of should we? So here's an example of the surface distribution of phosphate in the upper ocean or the distribution of phosphate in the surface ocean when the sun is shining. And you can see there's a huge amount of nutrient in the southern ocean all around the Antarctic continent in the subarctic Pacific and in the Eastern Equatorial Pacific. These regions are called high nutrient, low chlorophyll regions. So even though the sun is shining and the phosphate in the nitrate are extremely high, especially in the southern ocean, phytoplankton do not suck down the nutrients to near zero like they do in the rest of the world ocean where you see, for example, virtually no biomass or no nitrate or phosphate in the South Pacific or the Indian Ocean or the Atlantic Ocean. Now, what's the reason? Well, many years ago, John Martin, who was a eclectic chemist, thought that, well, we probably are overestimating iron and other elements in the ocean because we're contaminating them with the way we sample from ships. So he developed a technique after many years of struggle with the National Science Foundation that was a clean technique for measuring iron. And here is the distribution, for example, of iron. The scale is on the upper portion of the graph. And we have in the Pacific Ocean, for example, this is just the regular Pacific Ocean, less than 100 nanomolar, less than 100, I mean, 100 picomolar, less than 100 picomolar dissolve in organic iron. Now, molybdenum is very abundant, copper is by far much more, you know, even much more abundant. And what's the source of iron? Well, the primary source of iron to the oceans today is Aeolian iron. This is coming from deserts. So if you wanna reforest the world, and especially, for example, the Sahara Desert, the Gobi Desert and other deserts of the world, you're taking away a source of iron, ultimately, from the oceans. So it's, you are doing something that you don't understand to the ecosystems of the world of the oceans. And I should point out that the Sahara Desert was forested 4,000 years ago. Now, the distribution of iron or fluxes of iron from the atmosphere are asymmetrical because we have many more continental mass in the Northern Hemisphere than the Southern Hemisphere and it's seasonal and it's important. So this is an example of an iron fertilization experiment. So these are, this is the, this is two ships leaving from Christchurch in New Zealand. I just wanna show you how we do this. So here's the pre-cruise talks and here we're gonna dump the iron. So here's the mixed master. So here's iron in our jars, going in with a tracer into this big mixing vat. Here's the mixed master. We're gonna add a little acid to help dissolve it and then add a tracer. And here's the very expensive way we do it. A Costco hose with a lead weight tossed off the fantail of the boat, turn it on and you do that. All right, the way you do this is you go out and you start here and you go up and down like you're mowing a lawn seven kilometers by seven kilometers or approximately or eight kilometers by eight kilometers depending on the cruise. And then you know exactly where you started, you know exactly where you ended and you can then take the time as you sample back across and you go outside of the box and into the box that you put the iron in. And what happens is very, very, very quickly within 24 hours, for example, in this particular experiment, the photosynthetic rate is increased by a factor of two. So we can stimulate photosynthesis very, very, very rapidly by the addition of iron to the HNLC regions. Now, I'm just gonna make this point. This is not conceptual anymore. We've done this experiment at least 13 times. Not we, I mean, we as the scientific community have done it 13 times. So the first two experiments were done in the Eastern Equatorial Pacific with the late John Martin. And then we were the first to be third in the Southern Ocean and we, the Japanese have done it in the subarctic Pacific. You get blooms. You get phytoplankton blooms that sink. And yes, that can be a mechanism of taking CO2 out of the ocean. The issue is, if you do, I don't do these models, but some of my colleagues like Ken Caldera and Jorge Sarmiento and others have done these models. The problem is over a few hundred years, that biomass will be converted back into not just carbon dioxide, which would be okay. That would enhance the carbon pump. But it would remove oxygen in some areas of the ocean because of the respiration that is accompanying the mineralization. You make methane gas and potentially nitrous oxide. And the gases that are going to come out of the ocean in the centuries to come would be even more potent in terms of greenhouse gases than the carbon dioxide that would potentially come out. Now I just wanna finish this up with let's not forget the heat. It takes a lot more energy to warm water than the air. And so the ocean in timescales of decades, we can see changes in the heat content. This has been because we have incredibly accurate thermal measurements now, incredibly accurate to hundreds or thousands of a degree. And approximately 93% of the heat that would have been produced by increased CO2 in the atmosphere is actually stored in the upper 2000 meters of the ocean. Let me just show you this. This is only a six year record. And you can see there's a little bit of variability that is due to seasonal changes, but there's a long-term trend. And this trend we can continue. So we look at heat storage, not as temperature changes, but heat storage in joules per square meter. And this is really how we can calculate the transfer of heat from the atmosphere to the ocean. Now that means that the ocean, even if you stopped emitting CO2 today, zero, the ocean is going to be a source of heat back to the atmosphere of at least two tenths of a degree. So the ocean is a source of heat in the future. Now, what does that mean? It means from the point of view of you and I that there's going to be a change in sea level. And we see this as Sally pointed out, we can see changes in glacial biomass in Greenland, but the global cumulative change in glacial mass is enormous. And we're following this for a long time with a complicated two system, two satellite system. And I'm not going to go into that, but it's a very, very, very precise measurement of glacial mass. And I just want to point out that, for example, I'm not really worrying so much about the perennial ice, but it's glacial ice in Antarctica, which is the massive amount of ice that we should be worrying about. So the Western Antarctic Peninsula is one of the most rapidly warming places on the planet. And I'm just going to show you this. This is Bill Frazier. Bill has been working in the Antarctic for 30 something years. So in the 30 years or 40 years since he started, the area in the front of this graph from the Antarctic in Palmer Station, which is where we have a station for many years, that used to be all ice covered. And this year, for example, for the first time, when we were down in December, in the middle of the, the austral summer, for the very first time it was raining. We've never ever had rain in the 30 years of the LTER that we've been there. So I'm going to conclude that the fluxes of inorganic carbon between the atmosphere and the terrestrial biosphere on time scales essentially are largely controlled by chemical and physical processes. So I'm talking about the fluxes between the ocean and the atmosphere and terrestrial biosphere, right? Not the terrestrial biosphere independently. They can be manipulated by adding nutrients to the ocean with potentially harmful effects. And I'm just going to point out that the heat stored in the ocean is significant. It's not something that we can control anymore. So I'm going to end that there. Yes, thank you, Paul. That's food for thought, certainly. So we have a question. I'd like to go to Shafiq. Shafiq, would you like to unmute yourself and ask your question? Thanks, Paul. You kind of mentioned some of the unintended consequences of this phytoplankton and increasing this biological pump. Do we understand also the food chain potential in the ocean, the impacts of increasing kind of organic near the surface and kind of what that potentially has on the overall ecosystem of the animals and other plants in the ocean? Yeah, to some extent, it's quite straightforward in a way. So for example, the southern ocean is dominated by very large cells because the nutrients there, even though they're unconsumed fully, are very abundant. And the primary producer there are diatoms. So diatoms are relatively large cells that are consumed by krill, which are basically little shrimp, which are consumed by penguins, whales, seals. And so the food chain is very short. And because the food chain is very short, it's much more efficient than it is in the subtropics, for example, where the first cells that are formed are very small cells that are consumed by small zooplankton ciliates, which are single cells, which are then consumed by zooplankton, which are then consumed by small fish, which are then consumed by larger fish. So those changes in efficiency are going to lead to changes in the relative abundance of higher-order organisms over geologic time. So there's a very nice paper about this by Wolf Berger, who was a geologist at Scripps years ago. And he pointed out when we first formed the Antarctic continent about 30 million years ago when it broke off from the Drake, from the southern portion of the South America and became the first continent to be covered with ice for tens of millions of years, actually for hundreds of millions of years. That led to the, for reasons I'm not gonna bother you with, it led to the ecological dominance of these diatom organisms in the southern ocean. And that led to the evolution and ultimately success of whales. So whales re-entered the ocean from Melland, right? They're mammals. Basically they're hippopotamide that, you know, now are the largest mammals on the planet. And so their success was linked to this climate change that occurred 30 million years ago, which was driven by tectonics.