Showing posts with label ocean. Show all posts
Showing posts with label ocean. Show all posts
2010-10-25
The Whale Pump
It's this kind of shit that makes oceanography so hard... whale shit, literally. A new study suggests (and does not prove) [LINK][PLoS], that whale poop might pump nitrogen up to the surface in some areas of the oceans, acting as a boost to biological productivity (and consequently fish population). If this "whale pump" were eventually shown to be important in the global nitrogen cycle, how would climate models cope with that information? Who's going to code the whale_poop.F90 module? Geez.
2010-06-16
Why make a point when you can just sound like you are?
Just read an article on Reuters with the headline: Whale poo helps offset carbon footprint. Sometimes articles get stupid headlines because the person writing the article isn't in charge of making the headline, but this article actually says this in the text. It's real short, go read it. I doubt you'll be as angered by it as I am, but maybe you'll see how incredibly stupid it is.
The story reports on science, which says that sperm whales in the Southern Ocean defecate in the upper ocean where phytoplankton use the iron from the feces to grow. This in turn, allows the phytoplankton to "absorb" more carbon. The idea is just like iron fertilization.
The point that they article makes is that the cycle actually reduces atmospheric CO2 because the amount of carbon used by the phytoplankton is twice as much as is breathed out by the whales. Thus, Michael Perry (the reporter) concludes, the whales offset their carbon and reduce their carbon footprint.
First off, whales don't have feet, so they have no footprint.
Second, though, whales also don't use fossil fuels, so whales have no carbon footprint.
The science sounds interesting enough, and it seems like they are showing that this aspect of the carbon cycle is a net sink of atmospheric carbon. One caveat that isn't dealt with is that the phytoplankton don't necessarily use the carbon immediately die and sink, there is also a lot of recycling in the upper ocean. So this "carbon sequestration" (which just means that the phytoplankton die and sink to the deep ocean) might not be as strong as this news article would lead us to believe.
A larger point is that in the absence of humans, this would just be one of many small carbon sinks that would balance a lot of carbon sources, closing the carbon cycle. Unperturbed ecosystems, much less individual species, are (over long time scales) in steady-state. Imagine that humans disappear, so all the anthropogenic CO2 stays around, but no more is added. These whales(+phytoplankton) might continue to act as a net carbon sink, but over the long run, they aren't going to suck all the carbon out of the atmosphere. Okay, I'll stop belaboring this point.
What makes this an even better example of lazy science reporting is that the really interesting point about the whales'(+phytoplankton's) role in the carbon cycle is buried in the last sentence:
UPDATE:
An AP story also has most of this, but better covers the whaling angle: [LINK]
The story reports on science, which says that sperm whales in the Southern Ocean defecate in the upper ocean where phytoplankton use the iron from the feces to grow. This in turn, allows the phytoplankton to "absorb" more carbon. The idea is just like iron fertilization.
The point that they article makes is that the cycle actually reduces atmospheric CO2 because the amount of carbon used by the phytoplankton is twice as much as is breathed out by the whales. Thus, Michael Perry (the reporter) concludes, the whales offset their carbon and reduce their carbon footprint.
First off, whales don't have feet, so they have no footprint.
Second, though, whales also don't use fossil fuels, so whales have no carbon footprint.
The science sounds interesting enough, and it seems like they are showing that this aspect of the carbon cycle is a net sink of atmospheric carbon. One caveat that isn't dealt with is that the phytoplankton don't necessarily use the carbon immediately die and sink, there is also a lot of recycling in the upper ocean. So this "carbon sequestration" (which just means that the phytoplankton die and sink to the deep ocean) might not be as strong as this news article would lead us to believe.
A larger point is that in the absence of humans, this would just be one of many small carbon sinks that would balance a lot of carbon sources, closing the carbon cycle. Unperturbed ecosystems, much less individual species, are (over long time scales) in steady-state. Imagine that humans disappear, so all the anthropogenic CO2 stays around, but no more is added. These whales(+phytoplankton) might continue to act as a net carbon sink, but over the long run, they aren't going to suck all the carbon out of the atmosphere. Okay, I'll stop belaboring this point.
What makes this an even better example of lazy science reporting is that the really interesting point about the whales'(+phytoplankton's) role in the carbon cycle is buried in the last sentence:
Lavery said that without whaling there may have been 120,000 sperm whales in the Southern Ocean and, according to her calculations, some 2 million tonnes of carbon may have been removed from the atmosphere each year through this process.So what this says is that if the whale population was what it should be, the carbon source would be ten times larger (there are currently ~12,000 sperm whales in the Southern Ocean). So the interesting twist, in my opinion, isn't that the whales are "carbon negative," but really that whaling represents an increase in atmospheric CO2 by reducing a natural sink. This is just like (though much smaller than) land-use change, which removes carbon-absorbing ecosystems with cropland, removing a terrestrial sink. Does this raise the question of whether over-fishing represents such a decrease in a natural sink? So instead of going off half-cocked to do geoengineering through iron fertilization [e.g.], we should make a legitimate attempt to allow the natural ocean ecosystems to recover from the past couple of centuries of abuse.
UPDATE:
An AP story also has most of this, but better covers the whaling angle: [LINK]
2009-11-17
Trends in the central tropical Pacific
Well, since we've been thinking about the tropical Pacific, here's a bit more to ponder. There is an ongoing discussion in the literature about whether global warming, particularly across the tropical Pacific, will look more like El Nino or La Nina. One way this has tended to shake out is that the atmospheric scientists seem to favor El Nino conditions as the world warms, but oceanographers tend to lean toward La Nina [Eos]. The truth of the matter is that in the past couple of years, this has been shown to be a false analogy; it seems like there is evidence that the atmospheric circulation is changing to look somewhat more like El Nino, but changes in the ocean act against some of these atmospheric effects, looking more like La Nina. In fact, as these arguments mature, it seems like the dynamics involved are not really related to the dynamics that control El Nino and La Nina cycles [Vecchi].
The apparent controversy, though, is too good not to glom onto, and many authors have used it as a construct to present results. This is fine except that it clouds the emerging picture of climate change in the tropical Pacific.
A new paper by Nurhati et al (2009) includes this El Nino/La Nina kind of argument to highlight new isotopic measurements of coral reefs in the central Pacific. The geochemical techniques are applied to coral at three central Pacific islands, and show monthly-resolved temperature and salinity records over the 20th Century. The bottom line seems to be that there are statistically significant linear trends toward fresher, warmer water around these islands. The authors say that these trends are more consistent with more El Nino-like conditions in the central Pacific, are similar to other estimates of temperature changes, and is in line with modeling studies showing decreased upwelling of deep water in a warming world. Only in the final paragraph do the authors finally reveal that this El Nino stuff shouldn't be taken too seriously,
The apparent controversy, though, is too good not to glom onto, and many authors have used it as a construct to present results. This is fine except that it clouds the emerging picture of climate change in the tropical Pacific.
A new paper by Nurhati et al (2009) includes this El Nino/La Nina kind of argument to highlight new isotopic measurements of coral reefs in the central Pacific. The geochemical techniques are applied to coral at three central Pacific islands, and show monthly-resolved temperature and salinity records over the 20th Century. The bottom line seems to be that there are statistically significant linear trends toward fresher, warmer water around these islands. The authors say that these trends are more consistent with more El Nino-like conditions in the central Pacific, are similar to other estimates of temperature changes, and is in line with modeling studies showing decreased upwelling of deep water in a warming world. Only in the final paragraph do the authors finally reveal that this El Nino stuff shouldn't be taken too seriously,
... this analogy likely over-simplifies the complexity of tropical Pacific anthropogenic climate change. Indeed, any of a number of large-scale climate changes that are likely to occur in a greenhouse world might overwhelm or at the very least fundamentally reshape the expected impacts of an “El Niño-like” trend. ... In this regard, the prominent warming and freshening trends uncovered in the coral reconstructions undoubtedly represent a combination of dynamics that are fundamentally different than those associated with the ENSO phenomenon.
2009-11-14
The tropical ocean: more than just hurricanes
The Climate Prediction Center recently released a new El Nino Advisor [link]. The advisory says essentially that all indicators suggest that the current El Nino is still strengthening, and is expected to last through the winter and maybe into spring. It's likely, based on past El Nino events, that the largest anomalies of the tropical sea-surface temperature will happen some time in the next couple of months.
Recall that we knew this El Nino was forming last spring and summer, and that's why the Atlantic hurricane season was forecast to be relatively inactive. As we've seen, that forecast was pretty successful; we've only gotten up to "Ida" in the tropical storm names. The presence of El Nino conditions in the tropical Pacific ocean has effects that reach beyond hurricanes though, as this paragraph from the advisory lists:
So those of you up north and in Seattle can probably expect relatively mild winters, which might not be bad news! Meanwhile, California is expected to have a wetter than normal year, which so far looks to be true. Some of these correlations aren't very robust, so you can't really count on them, but so far they seem to be holding.
It is also worth noting that the effects of the tropical oceans are not limited to this kind of El Nino action. There's a flip-side to the story, too, which has come to be called La Nina. This is the cold phase of the oscillation, when the eastern tropical pacific is a bit cooler than normal. An interesting side effect of La Nina conditions in the tropical Pacific ocean is that precipitation tends to decrease over the central part of the USA, especially Texas, but extending north into the upper midwest and also west through the southwest and California. The Pacific Northwest and much of the southeast experience extra precipitation. The crazy thing is that it isn't just a seasonal effect, but can be clearly seen at longer time scales. A new paper by McCrary and Randall (2009, link) examines this relationship in observations and climate models, confirming what I've just said on timescales of 6 years and longer. Much of the paper deals with comparing three leading climate models with the observed 20th Century droughts in the USA. While they find that the models do capture some aspects/statistics of long-term drought in the central USA, none of the models seems to convincingly capture the relationships between tropical ocean variability and precipitation seen in the observations.
Of course, the fact that the models struggle to establish these connections between the tropics and the extratropics does not come as a great surprise. A key challenge for these comprehensive climate models is to produce realistic patterns and cycles of El Nino and La Nina. One of the models in McCrary & Randall (2009) is the Community Climate System Model (v3.0), which is known to have an overly regular cycle of El Ninos, with a period of about 2 years. Along with this regular cycle, the observed connections with remote regions is underrepresented. (link) So when looking for longer-term variations, it's unlikely for CCSM to have realistic patterns. In this case, the CCSM's long-term droughts don't seem to be very connected to the tropical oceans at all. The other models have different problems, but do notably better at establishing at least some relationship between cool tropical Pacific surface temperatures and increased likelihood of drought conditions in the central USA.
A key point to emerge from this analysis is that the climate models only marginally represent long-term droughts, and without very convincing physical processes compared to the observations. This means that these models are not necessarily proper tools for studying the frequency of droughts in the future. This hasn't stopped people from doing just that, as the authors note. So if you come across stories about changes in drought, pay close attention to the methods used, and keep a skeptical view of the findings. In the meantime, climate models are now being developed that have much improved representations of El Nino and La Nina (see link above, e.g.), so the next generation of climate models may have more credible (and interesting) droughts. And if you're an optimist, they might even teach us something about how the future of the USA's grain belt will look, and if you are very optimistic, maybe they won't point toward perpetual Dust Bowl conditions in the future.
Recall that we knew this El Nino was forming last spring and summer, and that's why the Atlantic hurricane season was forecast to be relatively inactive. As we've seen, that forecast was pretty successful; we've only gotten up to "Ida" in the tropical storm names. The presence of El Nino conditions in the tropical Pacific ocean has effects that reach beyond hurricanes though, as this paragraph from the advisory lists:
Expected El Niño impacts during November 2009-January 2010 include enhanced precipitation over the central tropical Pacific Ocean and a continuation of drier-than-average conditions over Indonesia. For the contiguous United States, potential impacts include above-average precipitation for Florida, central and eastern Texas, and California, with below-average precipitation for parts of the Pacific Northwest. Above-average temperatures and below-average snowfall is most likely for the Northern Rockies, Northern Plains, and Upper Midwest, while below-average temperatures are expected for the southeastern states.
So those of you up north and in Seattle can probably expect relatively mild winters, which might not be bad news! Meanwhile, California is expected to have a wetter than normal year, which so far looks to be true. Some of these correlations aren't very robust, so you can't really count on them, but so far they seem to be holding.
It is also worth noting that the effects of the tropical oceans are not limited to this kind of El Nino action. There's a flip-side to the story, too, which has come to be called La Nina. This is the cold phase of the oscillation, when the eastern tropical pacific is a bit cooler than normal. An interesting side effect of La Nina conditions in the tropical Pacific ocean is that precipitation tends to decrease over the central part of the USA, especially Texas, but extending north into the upper midwest and also west through the southwest and California. The Pacific Northwest and much of the southeast experience extra precipitation. The crazy thing is that it isn't just a seasonal effect, but can be clearly seen at longer time scales. A new paper by McCrary and Randall (2009, link) examines this relationship in observations and climate models, confirming what I've just said on timescales of 6 years and longer. Much of the paper deals with comparing three leading climate models with the observed 20th Century droughts in the USA. While they find that the models do capture some aspects/statistics of long-term drought in the central USA, none of the models seems to convincingly capture the relationships between tropical ocean variability and precipitation seen in the observations.
Of course, the fact that the models struggle to establish these connections between the tropics and the extratropics does not come as a great surprise. A key challenge for these comprehensive climate models is to produce realistic patterns and cycles of El Nino and La Nina. One of the models in McCrary & Randall (2009) is the Community Climate System Model (v3.0), which is known to have an overly regular cycle of El Ninos, with a period of about 2 years. Along with this regular cycle, the observed connections with remote regions is underrepresented. (link) So when looking for longer-term variations, it's unlikely for CCSM to have realistic patterns. In this case, the CCSM's long-term droughts don't seem to be very connected to the tropical oceans at all. The other models have different problems, but do notably better at establishing at least some relationship between cool tropical Pacific surface temperatures and increased likelihood of drought conditions in the central USA.
A key point to emerge from this analysis is that the climate models only marginally represent long-term droughts, and without very convincing physical processes compared to the observations. This means that these models are not necessarily proper tools for studying the frequency of droughts in the future. This hasn't stopped people from doing just that, as the authors note. So if you come across stories about changes in drought, pay close attention to the methods used, and keep a skeptical view of the findings. In the meantime, climate models are now being developed that have much improved representations of El Nino and La Nina (see link above, e.g.), so the next generation of climate models may have more credible (and interesting) droughts. And if you're an optimist, they might even teach us something about how the future of the USA's grain belt will look, and if you are very optimistic, maybe they won't point toward perpetual Dust Bowl conditions in the future.
2009-08-23
Tamino on methane release from sea floor
One of the scariest blog posts I've ever read: Tamino's Open Mind. I haven't been following these developments on possible evidence for methane clathrate instability, but clearly I should be, and we all should be.
2007-04-30
ye olde iron fertilizing effect
So apparently people now think they can make money by throwing iron into the ocean... YES, throwing iron into the ocean.
Here's the, actually very good, story on NYTimes.com: [The Energy Challenge: Recruiting Plankton to Fight Global Warming]
The basic idea is that plankton reproduce like mad when the conditions are right, and in large swaths of the ocean the conditions are right. Except there isn't enough iron. So, when you dump some iron on those areas, plankton bloom, creating regions of increased biological activity. The upside to this, according to some, is that the plankton use carbon from the ocean to make their little calcium carbonate exoskeletons, which when the critters die, can sink to the bottom of the ocean. This means that carbon is removed from the atmosphere-ocean system... it is sequestered, like an OJ juror. So now at least two companies, so cleverly named Planktos and Climos, think they can get governments (or companies working under cap and trade systems) to pay them to go throw some iron into the ocean.
I do not reject this idea outright. There are clearly some good ideas here, but we have to be careful. Here are a couple of my primary concerns.
First, I'm worried that these plankton species will produce a lot of methane waste, possibly negating any decrease in atmospheric CO2 that they might be responsible for. There is similar concern with nitrous oxide, apparently.
Second, the amount of carbon actually deposited might be less than has been thought recently. This is actually in this week's Science [LINK].
Third, as these operations scale up, will they account for their own carbon emissions. Boats are notoriously bad for emissions, and there's going to have to be a lot of boating involved. Also, where is this iron coming from, and how much energy (i.e., carbon) is going into collecting and transporting it?
Finally, there are possible feedbacks that could negate any good this will do. Including the old DMS-cloud condensation nuclei, in which more biology produces more aerosol (in the form of dimethylsulfide, DMS) which acts as nucleation sites for cloud droplets, making more cloud. The effect could be to shade the surface, reduce SST, and thus reduce biological productivity, leaving a rusty sea surface instead of a nice, healthy green one. I don't know if this is feasible, but things like this always seem to come up.
Also consider the amount of carbon dioxide that needs to be removed from the atmosphere. I've just come from a talk that reminded me of this. Carbon dioxide, when frozen, has about the same density as water. That means that a ton of CO2 is about one cubic meter (size of a coffee table). You're now talking about removing billions of tons of carbon dioxide annually, which is an enormous mass, many cubic kilometers of frozen CO2. The ocean is a big place, but we've got to be careful about how and where such deposits are made, or they'd just be mixed back up to the atmosphere. There's just so many potential pitfalls that it is hard to imagine a successful implementation. But as I said at the beginning, I'm willing to keep an open mind on the subject, and would be happy to see a successful strategy.
Here's the, actually very good, story on NYTimes.com: [The Energy Challenge: Recruiting Plankton to Fight Global Warming]
The basic idea is that plankton reproduce like mad when the conditions are right, and in large swaths of the ocean the conditions are right. Except there isn't enough iron. So, when you dump some iron on those areas, plankton bloom, creating regions of increased biological activity. The upside to this, according to some, is that the plankton use carbon from the ocean to make their little calcium carbonate exoskeletons, which when the critters die, can sink to the bottom of the ocean. This means that carbon is removed from the atmosphere-ocean system... it is sequestered, like an OJ juror. So now at least two companies, so cleverly named Planktos and Climos, think they can get governments (or companies working under cap and trade systems) to pay them to go throw some iron into the ocean.
I do not reject this idea outright. There are clearly some good ideas here, but we have to be careful. Here are a couple of my primary concerns.
First, I'm worried that these plankton species will produce a lot of methane waste, possibly negating any decrease in atmospheric CO2 that they might be responsible for. There is similar concern with nitrous oxide, apparently.
Second, the amount of carbon actually deposited might be less than has been thought recently. This is actually in this week's Science [LINK].
Third, as these operations scale up, will they account for their own carbon emissions. Boats are notoriously bad for emissions, and there's going to have to be a lot of boating involved. Also, where is this iron coming from, and how much energy (i.e., carbon) is going into collecting and transporting it?
Finally, there are possible feedbacks that could negate any good this will do. Including the old DMS-cloud condensation nuclei, in which more biology produces more aerosol (in the form of dimethylsulfide, DMS) which acts as nucleation sites for cloud droplets, making more cloud. The effect could be to shade the surface, reduce SST, and thus reduce biological productivity, leaving a rusty sea surface instead of a nice, healthy green one. I don't know if this is feasible, but things like this always seem to come up.
Also consider the amount of carbon dioxide that needs to be removed from the atmosphere. I've just come from a talk that reminded me of this. Carbon dioxide, when frozen, has about the same density as water. That means that a ton of CO2 is about one cubic meter (size of a coffee table). You're now talking about removing billions of tons of carbon dioxide annually, which is an enormous mass, many cubic kilometers of frozen CO2. The ocean is a big place, but we've got to be careful about how and where such deposits are made, or they'd just be mixed back up to the atmosphere. There's just so many potential pitfalls that it is hard to imagine a successful implementation. But as I said at the beginning, I'm willing to keep an open mind on the subject, and would be happy to see a successful strategy.
2006-12-12
meltdown
I don't have time to really think too hard about this story, but it is making the rounds, so I'll at least acknowledge it. Some NCAR simulations now predict essentially no late-summer ice in the Arctic by 2040. See the story at BBC [LINK] or at Nature [LINK]. The actual paper is in Geophysical Research Letters [doi:10.1029/2006GL028024].
What does this mean? Well, I haven't had a chance to look closely at the paper, but I have some first impressions. I did get a sneak-peek of these results this summer, and at the same time was introduced to some of the details of the sea-ice model used in CCSM (NCAR's climate model), so maybe I'll be able to say something halfway meaningful. The paper itself does not predict an ice-free Arctic in 2040, so let's just get that out of the way. This paper is really about the possibility of abrupt decreases in sea-ice in a changing climate, and the current generation of climate models suggest a real possibility of large reductions in perennial ice coverage in the first half of the 21st century. The main focus is a set of CCSM simulations using one of the emissions scenarios from IPCC. They also take a look at some of the results from other IPCC models. The CCSM always has what the authors call "abrupt reductions" in Arctic ice, and several of the other models also show large reductions.
I am willing to accept these results, but I think some skepticism has to be exercised still. First off, this is a GRL paper, which is a journal of short, usually preliminary, work focusing on "sexy" results. The peer-review process for GRL is sometimes thought to be a little lax, and sometimes the quality of the work is questionable. That does not seem to be an issue for this paper; the CCSM is a respected climate model, the authors are top-notch climate scientists, and this work is presented well. That said, this is not the last word on this project; I'm sure that the authors are doing more detailed work and are planning a longer, more careful analysis for another journal (e.g., Journal of Climate, Climate Dynamics). The best thing that could do would be to better quantify what "abrupt changes" really are, and the physical processes that trigger them, which is a big open question in this paper. They say the abrupt changes are driven by thermodynamics, but don't really present evidence of this; I assume they mean that wind patterns/ocean currents are changing to just move ice out of the Arctic, but it is not explained. The other thing to keep in mind is that even in the current generation climate models, the sea-ice models are fairly crude. I don't mean that in a bad way, the people working on these models are doing the best they can. Ice processes are quite complicated, and to properly model sea-ice, much like "properly" modeling clouds, the simulations need to be run in much higher resolutions. That kind of resolution is too expensive right now, and even if the resources were there, it would be a tough sell to dedicate it to the sea-ice component rather than better atmospheric and oceanic components. This particular climate model is known to be fairly sensitive, and when it gets knocked out of equilibrium, the sea-ice is one of the things known to respond fairly erradically. So while I think the CCSM, and several other high-end climate models, can get a lot of important changes correct, we still can't trust the details of these fully coupled simulations. My interpretation is then something like this: in the near future (50 years), it is likely that rapid reductions in perennial Arctic sea-ice will be observed, associated with (but not well-correlated with) increasing atmospheric greenhouse gases.
What does this mean? Well, I haven't had a chance to look closely at the paper, but I have some first impressions. I did get a sneak-peek of these results this summer, and at the same time was introduced to some of the details of the sea-ice model used in CCSM (NCAR's climate model), so maybe I'll be able to say something halfway meaningful. The paper itself does not predict an ice-free Arctic in 2040, so let's just get that out of the way. This paper is really about the possibility of abrupt decreases in sea-ice in a changing climate, and the current generation of climate models suggest a real possibility of large reductions in perennial ice coverage in the first half of the 21st century. The main focus is a set of CCSM simulations using one of the emissions scenarios from IPCC. They also take a look at some of the results from other IPCC models. The CCSM always has what the authors call "abrupt reductions" in Arctic ice, and several of the other models also show large reductions.
I am willing to accept these results, but I think some skepticism has to be exercised still. First off, this is a GRL paper, which is a journal of short, usually preliminary, work focusing on "sexy" results. The peer-review process for GRL is sometimes thought to be a little lax, and sometimes the quality of the work is questionable. That does not seem to be an issue for this paper; the CCSM is a respected climate model, the authors are top-notch climate scientists, and this work is presented well. That said, this is not the last word on this project; I'm sure that the authors are doing more detailed work and are planning a longer, more careful analysis for another journal (e.g., Journal of Climate, Climate Dynamics). The best thing that could do would be to better quantify what "abrupt changes" really are, and the physical processes that trigger them, which is a big open question in this paper. They say the abrupt changes are driven by thermodynamics, but don't really present evidence of this; I assume they mean that wind patterns/ocean currents are changing to just move ice out of the Arctic, but it is not explained. The other thing to keep in mind is that even in the current generation climate models, the sea-ice models are fairly crude. I don't mean that in a bad way, the people working on these models are doing the best they can. Ice processes are quite complicated, and to properly model sea-ice, much like "properly" modeling clouds, the simulations need to be run in much higher resolutions. That kind of resolution is too expensive right now, and even if the resources were there, it would be a tough sell to dedicate it to the sea-ice component rather than better atmospheric and oceanic components. This particular climate model is known to be fairly sensitive, and when it gets knocked out of equilibrium, the sea-ice is one of the things known to respond fairly erradically. So while I think the CCSM, and several other high-end climate models, can get a lot of important changes correct, we still can't trust the details of these fully coupled simulations. My interpretation is then something like this: in the near future (50 years), it is likely that rapid reductions in perennial Arctic sea-ice will be observed, associated with (but not well-correlated with) increasing atmospheric greenhouse gases.
2006-12-05
Down under, where the carbon is.
Today's little tidbit is a short news story about a Journal of Climate paper [LINK]. The paper is about a climate simulation that includes an ocean (and presumably a carbon cycle model). The bottom line is that they think they have a credible southern hemisphere atmospheric circulation, with then drives a realistic Antarctic circumpolar current. If you have never done so, go get a globe and look at it from the "bottom," so you are looking right at the south pole; notice that there is a ring of water around Antarctica. That's the only place where that happens, and it makes a big difference to the world's climate. Anyway, they say that as the winds around Antarctica move south, they change the uptake of carbon dioxide into the ocean, which partially offsets the climate change associated with the anthropogenic greenhouse effect. That's good! Unfortunately, it also accelerates sea level rise (by pumping heat into the ocean, raising the temperature faster) and ocean acidification (which might feed back onto the carbon cycle if critters start dying off). So there you go. Maybe I'll try to tap Nikki for more nuianced insight, since this is closely related to her work.
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