On noes! Antarctic sea ice may not cap carbon emissions as much as previously thought

From the “that darned sea ice is messing up our model” department and MIT News.

Study suggests sea ice blocks the flow of carbon both into and out of the ocean, in roughly equal measure.

The Southern Ocean surrounding Antarctica is a region where many of the world’s carbon-rich deep waters can rise back up to the surface. Scientists have thought that the vast swaths of sea ice around Antarctica can act as a lid for upwelling carbon, preventing the gas from breaking through the ocean’s surface and returning to the atmosphere.

However, researchers at MIT have now identified a counteracting effect that suggests Antarctic sea ice may not be as powerful a control on the global carbon cycle as scientists had suspected.

In a study published in the August issue of the journal Global Biogeochemical Cycles, the team has found that indeed, sea ice in the Southern Ocean can act as a physical barrier for upwelling carbon. But it can also act as a shade, blocking sunlight from reaching the surface ocean. Sunlight is essential for phytosynthesis, the process by which phytoplankton and other ocean microbes take up carbon from the atmosphere to grow.

The researchers found that when sea ice blocks sunlight, biological activity — and the amount of carbon that microbes can sequester from the atmosphere — decreases significantly. And surprisingly, this shading effect is almost equal and opposite to that of sea ice’s capping effect. Taken together, both effects essentially cancel each other out. 

“In terms of future climate change, the expected loss of sea ice around Antarctica may therefore not increase the carbon concentration in the atmosphere,” says lead author Mukund Gupta, who carried out the research as a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS).

He emphasizes that sea ice does have other effects on the global climate, foremost through its albedo, or ability to reflect solar radiation.

“When the Earth warms up, it loses sea ice and absorbs more of this solar radiation, so in that sense, the loss of sea ice can accelerate climate change,” Gupta says. “What we can say here is, sea ice changes may not have such a strong effect on carbon outgassing around Antarctica through this capping and shading effect.”

Gupta’s coauthors are EAPS Professor Michael “Mick” Follows, and EAPS research scientist Jonathan Lauderdale.

The role of ice

Each winter, wide swaths of the Southern Ocean freeze over, forming vast sheets of sea ice that extend out from Antarctica for millions of square miles. The role of Antarctic sea ice in regulating the climate and the carbon cycle has been much debated, though the prevailing theory has been that sea ice can act as a lid to keep carbon in the ocean from escaping to the atmosphere.

“This theory is mostly thought of in the context of ice ages, when the Earth was much colder and the atmospheric carbon was lower,” Gupta says. “One of the theories explaining this low carbon concentration argues that because it was colder, a thick sea ice cover extended further into the ocean, blocking carbon exchanges with the atmosphere and effectively trapping it in the deep ocean.”

Gupta and his colleagues wondered whether an effect other than capping may also be in play. In general, the researchers have sought to understand how various features and processes in the ocean interact with ocean biology such as phytoplankton. They assumed that there might be less biological activity as a result of sea ice blocking microbes’ vital sunlight — but how strong would this shading effect be?

Equal and opposite

To answer that question, the researchers used the MITgcm, a global circulation model that simulates the many physical, chemical, and biological processes involved in the circulation of the atmosphere and ocean. With MITgcm, they simulated a vertical slice of the ocean spanning 3,000 kilometers wide and about 4,000 meters deep, and with conditions similar to today’s Southern Ocean. They then ran the model multiple times, each time with a different concentration of sea ice.

“At 100 percent concentration, there are no leaks in the ice, and it’s really compacted together, versus very low concentrations representing loose and sparse ice floes moving around,” Gupta explains.

They set each simulation to one of three scenarios: one where only the capping effect is active, and sea ice is only influencing the carbon cycle by preventing carbon from leaking back out to the atmosphere; another where only the shading effect is active, and sea ice is only blocking sunlight from penetrating the ocean; and the last in which both capping and shading effects are in play.

For every simulation, the researchers observed how the conditions they set affected the overall carbon flux, or amount of carbon that escaped from the ocean to the atmosphere.

They found that capping and shading had opposite effects on the carbon cycle, reducing the amount of carbon to the atmosphere in the former case and increasing it in the latter, by equal amounts. In the scenarios where both effects were considered, one canceled the other out almost entirely, across a wide range of sea ice concentrations, leading to no significant change in the carbon flux. Only when sea ice was at its highest concentration did capping have the edge, with a decrease in carbon escaping to the atmosphere.

The results suggest that Antarctic sea ice may effectively trap carbon in the ocean, but only when that ice cover is very expansive and thick. Otherwise, it seems that sea ice’s shading effect on the underlying organisms may counteract its capping effect.

“If one just considered the physics and the pure capping, or carbon barrier idea, that would be an incomplete way of thinking about it,” Gupta says. “This shows that we need to understand more of the biology under sea ice and how it underlies this effect.”

Source: Jennifer Chu | MIT News Office

The paper: “The effect of Antarctic sea ice on Southern Ocean carbon outgassing: Capping versus light attenuation”

53 thoughts on “On noes! Antarctic sea ice may not cap carbon emissions as much as previously thought

    • Yup!

      The science is so settled that the role of ice in preventing heat radiating up from the warmer ocean underneath is completely ignored in favour of sone nebulous warming effects of a very rare trace gas completely misnamed ‘carbon’ in this study.

      There are none so blind as those who refuse to see.

    • “the expected loss of sea ice around Antarctica may therefore not increase the carbon concentration in the atmosphere”

      Yeah, but as we are not warming, their expectations are worthless. It’s amazing that scientists do not see their inherent bias by assuming global warming. It is up to any good scientist to question ALL of their assumptions, yes even the climate, when putting together a thesis particularly if it is pivotal to the thesis.

      These are amateurs.

      Just finished reading “Lost City of the Monkey God.” It was a good book until the end when discussing the leishmaniasis (parasite transmitted by sand fleas) that half the expedition contracted. The author explained the presence of this parasite in Texas and another state based on climate change and assumed global warming allowing it to move North.

      How about the introduction of 100s of thousands of illegal people from Central America into the US over the last 15 years or more. I would not claim a movement of the tropical vector North due to climate until ruling out the introduction of diseased illegal aliens and the possibility of a new vector, mosquitoes instead of sand fleas, for parasite transmission.

  1. Antarctic might have peaked for the year two days ago, but have to wait and see. Its high so far was 18.952 sq km on the 28th, according to the NSIDC.

    That’s higher than any year since the 2014 record (2013 and 2012 were also well above average), ie higher than the maxima in 2015, 2016, 2017, 2018 and 2019. So Antarctic sea ice has recovered from the two freakish weather events in Super El Nino 2016, which produced a record low maximum in 2017.


    This year was also higher than 2011, 2010, 2008, 2003, 2002 and 2001, among years this century. Also higher than 1979. I didn’t check all the intervening 20th century years. but 2020 is well above the median.

  2. ” the team has found that indeed, sea ice in the Southern Ocean can act as a physical barrier for upwelling carbon”

    How can that be? I thought carbon was heavier than water….

    • It’s interesting they only speak of outgassing and capping. Both at the Arctic and Antarctic we have CO2 sinks.

  3. Word search on “Carbon” = 30, and for “Dioxide” & “CO2” = Zero

    Is there some rational reason for harping on Carbon and not CO2 or Carbon dioxide? I chalk it up to pure propaganda (carbon is black), but then maybe it does make sense for some reason.

    • They might say they are concerned about how carbon cycles within global systems, but your point is absolutely correct. It’s really about CO2 and how it’s cycled in and out of the atmosphere.

    • Either they are too lazy to say Carbon Dioxide, are being too thrifty with word count, or they really don’t know the difference between Carbon and Carbon Dioxide. Considering the quality of work coming from the “Carbon Crowd” it is probably the latter.

      • It’s such lazy/stupid use of the language that moved me in the direction of being a skeptic. I doubt physicists or chemists use such sloppy language when they write on their topics. At least, I haven’t seen it.

      • It’s interesting to note that the paper itself see link above that WUWT provided also uses “Carbon” as the predominant verbiage in their plain language summary:

        Word search results on:
        “Carbon” = 9
        “CO2” = 5
        “Dioxide” = zero

    • I chalk it up to pure propaganda (carbon is black)

      Not quite. Graphite is gray. Most diamonds are pretty clear, and pretty pretty.

      Very versatile stuff, carbon, hence life is based on it. Personally, I’m a big fan. If you have any of that clear carbon, I’ll take it off your hands…

  4. Instead of just playing games on this MITgcm program, maybe they could add in a Sim City module? Then maybe they could have lots and lots of solar heated greenhouses situated around Antarctica, growing giant trees while soaking up the CO2.

    Such fun!

  5. It seems to me very hard to predict what will happen when co2 goes up. Too many unknowns. When a complex system changes it is very hard to predict what mechanisms will change to reach new equilibrium. The models are simply toy models that may or may not match the future.

    • Too me it is very similar to pharmaceutical drugs that are being developed. The science models often predict the drugs will work but often they turn out to fail in real trials. The reason is that despite all that science knows about the human body there are many unknowns and the biological models do not fit reality well enough.

      • Or the drug might have a different effect than predicted. Like when they were testing some new heart pill, and it had no effect on the heart, so they decided to end the trial. But the patients asked to please continue taking the medication. It took some awkward conversation behind closed doors until the scientists found out that the new medication did something to a different organ. And then they got rich with the little blue pills.

  6. “This shows that we need to understand more of the biology”

    = Send us a another grant cheque !!!

  7. To continue on with their computer games, these rent-seekers at MIT are steadfastly ignoring the actual data from the OCO-2 results published in 2017.

  8. Is this the much talked about “Cap and Shade“emissions control program, we have heard so much about?

  9. So if had my time over and had aspirations of becoming a “climate scientist”, would I enroll to study –
    a) astronomy
    b) oceanography
    c) geology
    d) physics
    e) chemistry
    f) biology
    g) atmospherics
    h) meteorology
    i) statistics
    j) mathematics
    k) paleontology
    l) political science
    m) psychology


    (I won’t mention “ethics” as this discipline seems to have no applicability to “climate science”)

        • Is that maybe a redirect to the onion?

          I made it part way through the abstract

          Noticed one woman author, out of 4, were they just patronizing her?

        • We roasted this paper a while ago. But the abstract is pure comedy gold:

          “Glaciers are key icons of climate change and global environmental change. However, the relationships among gender, science, and glaciers – particularly related to epistemological questions about the production of glaciological knowledge – remain understudied. This paper thus proposes a feminist glaciology framework with four key components: 1) knowledge producers; (2) gendered science and knowledge; (3) systems of scientific domination; and (4) alternative representations of glaciers. Merging feminist postcolonial science studies and feminist political ecology, the feminist glaciology framework generates robust analysis of gender, power, and epistemologies in dynamic social-ecological systems, thereby leading to more just and equitable science and human-ice interactions.”

  10. “This shows that we need to understand more of the biology under sea ice and how it underlies this effect.”

    Yes geochemists and physicists generally ignore biology, and these ones don’t seem to have thought it helpful to include one in the study. Perhaps they know that biological science was the first one to be close to being totally destroyed by activism. Hmm.. on the other hand, why didn’t they choose one of those to add more alarm?

    This study imagines biological agents to be helpless as the ice extends (the trusty old petri-dish model of living things – e.g. when sea level rises, a billion will drown).

    Humpback whales swim from the Arctic to Carribean, have their offspring and thence with calf to Antarctic waters to feed on tons of krill. Somehow the Krill seem to cope. Were any objective scientist studying this matter, they would first off suspect that plankton move to keep the sun shining on them, or, multiply like crazy only beyond the fringe of frozen water. Then they would interview a planktonologist or whatever they might be called.

  11. I think ice allows the flow of carbon dioxide. I know that when I put ice in my water, I can add much more carbon dioxide to my drink than if I cool the water down with ice and take the ice out right before I add the carbon dioxide. While I understand that without the ice the water can warm, but i do not think it can warm much in the 30 seconds it take me to pour the water into the jar. Since it cannot be the water taking on the added co2 since both are close enough to the same temperature, I think the ice is absorbing it.

    Thought that maybe someone could run with this somewhere.

    • Colder water absorbs more CO2 than warmer. However, this is a different effect. They’re talking about the ice physically blocking the CO2 from escaping into the atmosphere.

      • Which is, indeed, quite ludicrous. It’s a bit like claiming that putting cows in a barn would prevent their exhaled CO2 from getting into the atmosphere outside of the barn.

        The CO2 under the ice will be absorbed by greedy plant life, and be recycled into something edible to animal life, like it always is.

  12. Antarctic ice extent is growing like crazy. This paper is likely a way to get ahead of this with ice growth is a bad kind of climate change that comes out of fossil fuel burning.

  13. A climate revolving around carbon is as nonsensical as the sun and stars revolving around the earth 🌍 .

  14. The researchers found that when sea ice blocks sunlight, biological activity — and the amount of carbon that microbes can sequester from the atmosphere — decreases significantly.

    Maybe that’s why at the inception of all the glacial intervals in the current Pleistocene, CO2 in air continued to increase centuries or millennia after the onset of glaciation.

    For instance high CO2 persisted for 5000 years after glacial inception at the termination of the Eemian interglacial:


    The same is true of the ancient glaciation at the end of the Ordovician era, the one that puzzles climate scientists since it happened while CO2 in air was high. Again CO2 increased as the glaciation spread and moved equatorwards.


  15. The ice might block the CO2 near Antarctica, but that water will flow out from underneath it sooner or later.

  16. “Taken together, both effects essentially cancel each other out. ” As a Christian I like to think God has got this all figured out. He has natural processes in place to keep the balance. For man to think they have the power to wreck God’s creation is similar to the Tower of Babel story. Other than a nuclear holocaust, man’s impact is puny.

  17. “The researchers found that when sea ice blocks sunlight, biological activity — and the amount of carbon that microbes can sequester from the atmosphere — decreases significantly.”

    Ya think!?!

    What were they doing guessing at these processes and not really knowing, yet proclaiming the end of the Earth as we know it? They have no shame, no skill, no data.

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