Antarctic Sea Ice and Global Warming

Did you ever leave your freezer door slightly open on a humid day only to find chunks of new ice formed at the gap? When that happens, did you conclude “Oh, my freezer is colder than usual, I wonder how that happened?” No. You concluded that you had left the door slightly open, some cold got out, and vapor froze on your gasket.

Sea ice is hard to make. The sea is salt water, so it has a lower freezing point than fresh water. The sea has potentially large waves and lots of currents. This is just not a situation where ice can easily form. Yet, it does form on the oceans near the Earth’s poles because it is really cold there. But even within that context, more or less ice can form because of important details like how much fresh water is mixing in with the cold salt water, and exactly where currents of warmer or colder water are going. The formation of sea ice at the ends of the Earth is probably somewhat more complicated than the formation of frost and rind on your refrigerator.

(A quick note: Sea ice is ice that sits on, and therefore, essentially, in the sea. It is not glacial ice. Those are two very different things. I’m sure you knew that but just in case this is a good moment to point it out.)

In recent years, the amount of sea ice forming around Antarctica has bee going up. Global warming causes local warming but it also causes local cooling (like when the Arctic Vortex got knocked off center last winter and visited the middle of North America, an event that still causes a sense of fear and loathing among those of us who experienced it). So when we hear about expanding sea ice in the Antarctic, knowing that anthropogenic global warming is a real thing, we might assume that this is just one of those phenomena that runs counter to expectations but that is still part of the overall process of warming-driving climate change resulting from the addition of greenhouse gasses to the atmosphere.

And that is essentially correct, though the reasons may be a bit unclear and require further study.

So, thinking about our freezer, and the overall problem of making sea ice, there seem to be three things that can cause more of this ice. One might be the addition of fresh water to the system. That seems likely if the Antarctic glaciers are melting (which they are). Depending on where the fresh water goes, that could allow the formation of sea ice. Also, if precipitation increased in the area, that would add fresh water.

Second, the area where the sea ice is forming could be colder. That seems backwards in on a warming planet, but actually, that can happen too. Antarctica is, to a larger extent than the Arctic, a semi-closed system of air and sea currents, because it is a roundish continent surrounded by sea at one end of the planet. This means that cold air might be retained over the continent rather coherently. At the North Pole, “Winter (January) temperatures … can range from about −43 °C (−45 °F) to −26 °C (−15 °F), perhaps averaging around −34 °C (−29 °F),” while at the South Pole, “In winter, the average temperature remains steady at around −58 °C (−72 °F).” (source: Google). The north pole is sea, the south pole is land, and the south pole is at a higher elevation, but those differences are partly why the south pole is colder. Anyway, with all this cold air on the Southern Continent, perhaps one only needs to have air currents change a little to move that cold air over the sea a bit more to add to the chances of freezing water and making sea ice.

Third is the possibility that the disruptive effects of storms, waves, or surface currents could change, making for a calmer environment, allowing more ice formation.

Have any of these things happened?

Yes. Yes, they have.

Joe Romm has a writeup on some recent research that helps to explain the increase in Antarctic Sea ice (NOAA: Record Antarctic Sea Ice Growth Linked To Its Staggering Loss Of Land Ice).

The National Snow and Ice Data Center notes:

…sea ice surrounding the Antarctic continent reached its maximum extent on September 22 at 20.11 million square kilometers (7.76 million square miles). This is 1.54 million square kilometers (595,000 square miles) above the 1981 to 2010 average extent, which is nearly four standard deviations above average. Antarctic sea ice averaged 20.0 million square kilometers (7.72 million square miles) for the month of September. This new record extent follows consecutive record winter maximum extents in 2012 and 2013. The reasons for this recent rapid growth are not clear. Sea ice in Antarctica has remained at satellite-era record high daily levels for most of 2014.

“What we’re learning is, we have more to learn,” said Ted Scambos, lead scientist at NSIDC.

The unusual sea ice growth in Antarctica might be caused by changing wind patterns or recent ice sheet melt from warmer, deep ocean water reaching the coastline, according to scientists at NSIDC. The melt water freshens and cools the deep ocean layer, and it contributes to a cold surface layer surrounding Antarctica, creating conditions that favor ice growth.

From Skeptical Science:

The most common misconception regarding Antarctic sea ice is that sea ice is increasing because it’s cooling around Antarctica. The reality is the Southern Ocean surrounding Antarctica has shown strong warming over the same period that sea ice has been increasing. Globally from 1955 to 1995, oceans have been warming at 0.1°C per decade. In contrast, the Southern Ocean (specifically the region where Antarctic sea ice forms) has been warming at 0.17°C per decade. Not only is the Southern Ocean warming, it’s warming faster than the global trend. This warming trend is apparent in satellite measurements of temperature trends over Antarctica…

And, from NOAA:

Much of this year’s sea ice growth occurred late in the winter season, and weather records indicate that strong southerly winds blew over the Weddell Sea in mid-September 2014. Antarctica is a continent surrounded by open ocean. So unlike the Arctic, where surrounding landmasses constrain how much sea ice can expand, Antarctic sea ice can spread out over a bigger area. Winds blowing from the land toward the ocean encourage ice growth in the waters north of the continent.

Winds probably did not act alone to spur so much sea ice growth; melting land ice may have played a role. Most of Antarctica’s ice lies in the ice sheets that cover the continent, and in recent decades, that ice has been melting. Along the coastline, ice shelves float on the ocean surface, and much of the recent melt may be driven by warm water from the deep ocean rising and making contact with ice shelf undersides.

How does the melting of land ice matter to sea ice formation? The resulting meltwater is fresher than the seawater. As it mixes with the seawater, the meltwater makes the nearby seawater slightly less dense, and slightly closer to the freezing point than the ocean water below. This less dense seawater spreads out across the ocean surface surrounding the continent, forming a stable pool of surface water that is close to the freezing point, and close to the ice onto which it could freeze.

Added cold seems to be a factor. Added fresh water seems to be a factor. Changes in where cold air and relatively fresh water goes seems to be a factor. I don’t know about storminess and currents at the outer edge of ice formation.

The dramatic and steady increase in Antarctic Sea Ice is yet another example of the effects of climate change.


  1. #1 Desertphile
    October 9, 2014

    “When that happens, did you conclude ‘Oh, my freezer is colder than usual, I wonder how that happened?’”

    No. But then, I’m not an idiot. Meanwhile, the denialosphere is crammed full of people who claim to believe it…..

  2. #2 Frosty
    October 9, 2014

    It is worth asking if the same phenomenon is observed around Greenland. They have experienced significant glacial melt, thus adding freshwater to the surrounding ocean. My bet is on the increase in southerly winds causing the Antarctic sea ice anomaly. Between 2010 and 2012, strong northerly winds caused record winter sea ice in the Bering Sea. When those northerly winds did not materialize last year, the Bering Sea sea ice concentration returned to below average.

  3. #3 Greg Laden
    October 9, 2014

    My guess is that the overall situation in Greenland vs. the southern continent is so different that the comparison is not easy to make. In particular, the currents in the two regions probably do very different things with the meltwater.

    Also, I believe antarctic is putting much more fresh water out than Greenland, though over a much larger area, so that would have to be worked out.

  4. #4 Harry Twinotter
    October 9, 2014

    Another explanation was the polar vortex has increased so this pushes the ice extent outwards. Areas that were freed of ice as consequence then refreeze on contact with the cold air thus forming more ice. “Ice factories” was the term they used I think.

    Regardless of the cause the ice is seasonal and does not accumulate as multi-year ice, it disappears the next summer.

  5. #5 Bob Bingham
    October 9, 2014

    The big threats from melting ice are from Greenland and Antarctica where most of the worlds water is frozen into ice.

  6. #6 Stevo Raine
    October 10, 2014

    Good article and analogy here.

    Sounds like all those things are factors here. Recall reading / hearing somewhere that the stronger Antartican vortex winds were responsible for a lot of that sea ice expansion and also driving much of the heat and /or carbon dioxide into the southern ocean too.

    “.. Not only is the Southern Ocean warming, it’s warming faster than the global trend. “

    From my understanding here (I am NOT a climatologist so take with pinch of sodium chloride) , the polar regions are expected by the science to heat up much faster and more dramatically than the rest of our planet, yes?

  7. #7 Stevo Raine
    October 10, 2014

    Just had a quick look on the ABC news website and found :

    ‘Southern Hemisphere ocean warming ‘underestimated’

    “Previous estimates of global ocean warming have been significantly underestimated due to historically sparse temperature data from the Southern Ocean, new research has found.”

    Plus :

    Faster westerlies threaten Antarctica’

    “Heat-bearing westerly winds have picked up speed in the past 50 years are likely to be contributing to the melting of Antarctica’s Larsen ice shelf, say scientists.”

    In addition to :

    “Frequency of storms could help explain why sea ice is spreading around Antarctica but melting rapidly in the Arctic, say Australian researchers.

    Melting continental ice shelves in Antarctica could also encourage the growth of sea ice there, adds climate scientist Professor Ian Simmonds from the University of Melbourne.”

    Which is the ‘Storms whip up differences in polar sea ice’ article which I think was the one I was thinking of above.

    Might’ve been on the Catalyst TV science show or mentioned on the radio some months ago too.

    Anyhow, all this definitely reinforces and supports and is entirely consistent with the other links and article here so hope that helps.

  8. #8 Omega Centauri
    October 10, 2014

    I think we are finding more than a single change is part of this. For a while the main explanation was the southern annular mode (SAM), which are a fancy name for the circumpolar winds. have gotten stronger, and this bottles up the cold air. One causative factor was assumed to be the ozone loss changing the ( very high altitude winds. Of course winds effect surface currents and ice formation or breakup etc.)

    I think summer sea ice is getting lower around Antarctica,
    so we have different seasons. This has greater biologic and glacial implications than the winter sea ice.

    Now we have salinity/temperature driven currents. Warmer salty water flows south at medium depth. Cooler fresh water near the surface forms a cap, keeping this heat away from the seaice. But the warm salty water can contact the bottom of floating ice shelves (hundreds of meters thick glacial origin ice), and this is a major factor in melting the iceshelves. Now there is more fresh water, and that means more freash water near the surface flowing north, and more warm salty mid-depth water coming south, where it increases the iceshelf melting rate (and fresh water formation). Most likely at least these two things are contributing to the result.

  9. #9 See Noevo
    October 10, 2014

    Is the same thing happening in the Arctic? If not, what happened to the freezer door?

  10. […] No doubt you’ve seen the headlines, in some quarters (ahem, the usual suspects), screaming out the news of Antarctic sea ice hitting an all-time high. Whew! Global warming averted! Of course that’s not the case at all. It just means there’s more moisture in the coldest continent on Earth. Greg Laden had this great write-up: […]

  11. #11 Richard Chapman
    October 11, 2014

    The climate is so complex that I suspect we will not learn the whole story of the Arctic sea ice expansion until low-lying coastal cities are building sea walls.

  12. #12 Greg Laden
    October 11, 2014

    See, no, an entirely different thing is happening in the Arctic, where there is a sea instead of a continent.

  13. #13 Rob Honeycutt
    October 11, 2014

    Richard… Careful. It’s Antarctic sea ice that’s expanding. Arctic sea ice is in rapid decline. Also note that sea ice contributes very little to sea level rise. It’s land based ice that does that, and both Greenland and Antarctic ice mass are also in rapid decline.

  14. #14 Francis Smith
    District of Columbia
    October 11, 2014

    Hello–I really enjoyed this article–anything to make the world make more sense is great.

    I write though to say, that in the fridge left ajar what forms is properly called rime, not rind.

    I thought you’d want to know this, and truly, when you moderate this comment, there is no need to post it! It’s simply an FYI.

    All the best,

  15. #15 Greg Laden
    October 11, 2014

    Thank you for the comment. Rind is actually correct as well.

  16. #16 Rob Honeycutt
    October 11, 2014

    In aviation it’s called “rime ice” and is something one tries to avoid (understatement).

  17. #17 Rob Honeycutt
    October 11, 2014
  18. #18 GY
    February 2, 2015

    Arctic ice volume increase?
    More multiyear ice.

    “Arctic sea ice volumes in the autumn of 2014 are above the average set over the last five years and sharply up on the lows seen in 2011 and 2012, according to the latest satellite data. ”

    “This is the second year in a row where a relatively cool Arctic summer has led to less sea ice melting than has been typical during the summers of recent years and this has resulted in thicker and older ice surviving into the autumn and winter during both 2013 and 2014. “

  19. #19 GY
    February 2, 2015

    Antarctic sea ice also much thicker than expected.

    “According to climate models, the region’s sea ice should be shrinking each year because of global warming. Instead, satellite observations show the ice is expanding, and the continent’s sea ice has set new records for the past three winters. At the same time, Antarctica’s ice sheet (the glacial ice on land) is melting and retreating.”

  20. #20 Greg Laden
    February 2, 2015

    GY: Why would the ice shrink every year because of global warming? That is not at all what is expected.

  21. #21 Greg Laden
    February 2, 2015

    Again, both of these are expected. We expect something like Arctic ice volume or surface area to vary from year to year, up and down, with a general downward trend until that shift to a “new normal” is complete. We expect Antarctic ice to be more common if there is a change in the availability of fresh water to enhance freezing, which there is. Meanwhile, Greenland glaciers and Antarctic glaciers are melting at an increased rate. All of this is what we expect with global warming.

  22. #22 Tim
    February 2, 2015

    I don’t suppose active volcanoes under the ice lubricating the glaciers and sliding the shelf faster out to sea would have much to do with anything?

    “It’s not just the fact that there is melting water, and that water is coming out,” Schroeder told Live Science. “It’s how that affects the flow and stability of the ice.”

  23. #23 Greg Laden
    February 2, 2015

    Tim, yes, there are volcanoes on pretty much every continent!!! There are hot spots and volcanoes under the Antarctic Ice. The same source you site also notes “West Antarctica is also hemorrhaging ice due to climate change, and recent studies have suggested there is no way to reverse the retreat of West Antarctic glaciers.”

    It is hard to say how important the volcanoes are. My understanding is that more research is needed. But the rate of melting of these glaciers is linked primarily to human induced global warming.

  24. #24 GY
    February 2, 2015

    “Greenland glaciers and Antarctic glaciers are melting at an increased rate. All of this is what we expect with global warming.”
    And what we’d expect if geothermal activity under the ice were increasing.

    “The Greenland ice sheet is melting from below, caused by a high heat flow from the mantle into the lithosphere. This influence is very variable spatially and has its origin in an exceptionally thin lithosphere. Consequently, there is an increased heat flow from the mantle and a complex interplay between this geothermal heating and the Greenland ice sheet. The international research initiative IceGeoHeat led by the GFZ German Research Centre for Geosciences establishes in the current online issue of Nature Geoscience (Vol 6, August 11, 2013) that this effect cannot be neglected when modeling the ice sheet as part of a climate study.

    Read more at:

    As for the thicker arctic sea ice, not so long ago when the surface area of sea ice recovered to some extent there was wailing and gnashing of teeth because that ice wasn’t thick multi year ice.
    Now the ice is thicker multi year ice and in greater volume than in the previous five years so its somehow no longer important.

    I had suspected long ago that geothermal activity, along with increased solar activity played a part in warming of ocean waters and melting of ice. Now it looks like I had good reason to believe that.

    The breech in the Magnetosphere may also play a part. Not sure exactly how, but that’s a mighty powerful force to simply ignore.

    As for all this being unstoppable well that’s been mother natures way of doing things all along. No one can stop a glacier from doing anything. All we can do is observe.

    I suppose we could encourage a nuclear exchange between Russia and Red China, that would put a end to rice paddy methane production in China and much of Asia, destroy all heavy industry in eastern Europe, and give us a few years of nuclear winter to off set the present warming trend.
    The soft glow from the glassed over craters where major cities once stood might reflect off the clouds of ash and reduce the need for streetlights in the remaining cities.
    Drifting ash clouds would end commercial aviation, so that would greatly reduce use of petroleum based jet fuels.
    Population would drop dramatically, and fewer viable pregnancies along with mostly sterile offspring would keep population down for centuries.
    Hey, win-win all around.
    Save the planet-kill the people. Just like the 50-60’s sci fi movies where nukes could solve every problem.

  25. #25 Greg Laden
    February 2, 2015

    “And what we’d expect if geothermal activity under the ice were increasing.”

    But it isn’t, and that link does not make that claim. Please avoid mischaracterizing evidence on this blog in the future. You’ve been doing that a lot and I am becoming annoyed.

    “he surface area of sea ice recovered to some extent there was wailing and gnashing of teeth because that ice wasn’t thick multi year ice.” There was no recovery. There is simply an expected amount of inter annual variability. This will be true of both sea ice extent and thickness.

    “I had suspected long ago that geothermal activity, along with increased solar activity played a part in warming of ocean waters and melting of ice.”

    There has been a decrease in solar activity, so, no.

    This Gish Gallop of yours is getting Tiresome, GY. No more.

  26. #26 Brainstorms
    February 2, 2015

    Greg: “Sealion”.

    All along he’s been very cleverly wasting your time.

  27. #27 Tim
    thumbing through pirated 3-d printable CAD files pilfered from Arcs'R'Us
    February 2, 2015

    We might be talking about a boiling hot magma spewing, newly awakend volcano here and not just a couple hundred milliwatts/m^2 of ‘thin lithosphere’ –These articles seem to hint at that:

    Inevitable eruption will speed up ice loss on frozen continent, study says.

    As you have suggested, Greg Laden, further researching it would seem to be prudent..

    Most of the seismometers used to discover the volcano have been removed and installed in other areas in Antarctica, so further study of its seismic activity is no longer possible.

    “The volcano will create millions of gallons of water beneath the ice – many lakes full. This water will rush beneath the ice towards the sea and feed into the hydrological catchment of the MacAyeal Ice Stream,