FROM THE FIELD
American Geophysical Union Fall Meeting

Deep Ocean Heat Is Melting Antarctic Ice

by |December 14, 2010

Like dirt swept under the carpet, some of the human-made heat produced over the last century has been getting soaked up by the world’s oceans, and sinking into deep waters. Now, it is coming back to haunt the surface, in a very sensitive place: western Antarctica, where vast ice sheets meet the ocean. The result appears to be that ice is rapidly being eaten from the bottom, says Douglas Martinson, a polar scientist at Lamont-Doherty Earth Observatory, who presented the findings Monday at the fall meeting of the American Geophysical Union.

Warm waters carried by the Antarctic Circumpolar Current are brushing the ice front in the western part of the continent, in the area of the Bellingshausen Sea.

Warm waters carried by the Antarctic Circumpolar Current are brushing the ice front in the western part of the continent, in the area of the Bellingshausen Sea. (Click to enlarge. Courtesy Douglas Martinson, Lamont-Doherty Earth Observatory)

Martinson said that heat stored in deep waters far from Antarctica is being pushed southward and becoming entrained in the Antarctic Circumpolar Current, a vast, wind-driven water mass that constantly circles the frozen continent. The evidence comes from 18 years of Antarctic voyages Martinson has made to measure water temperature, salinity and other qualities at different depths. He called the increases in ocean heat in the past few decades “jaw dropping.” Temperatures have risen only a few degrees above the melting point–but that is all it takes to cut at the ice front. “This is like a huge freight of hot coals–fresh, hot water being delivered right to the the front door,” he said.

This raises the specter of sea-level rise driven by melting in this region–but there is a larger implication, said Martinson. Even if all sources of human-produced carbon dioxide in the air were cut off, the built-up heat will remain in the ocean for many years to come. “Pretend your brains out that the politicians did something to stop global warming tomorrow.  Even if they did, we will still have decades and decades of upwelling of that warmed water eating ice,” he said.

Read a Discovery News article about Martinson’s talk.

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YoronDoug MartinsonBarryDavid LewisJason Recent comment authors
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Jason
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Jason

This may be a naive question, but could you explain how warm water sinks in the first place?

Doug Martinson
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Doug Martinson

Jason — Your comment is not naive, it is very common. When we say “warm” water in polar regions, we are talking relative to the freezing point. So in the above report, warm refers to waters that are 3.5 to 4 degrees warmer than freezing. That is blazing hot for ice (water will melt over 4300 times more ice than air given air and water of the same volume and temperature). But, this hot water is still so cold I wear special scuba gloves when sampling it. Anyway, in most of the oceans where the water temperature is actually warm… Read more »

David Lewis
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David Lewis

I’m trying to understand what scientists know about what the changes in the Southern Westerlies mean for the Antarctic region and for global climate change. I’ve heard Joellen Russell vividly describe that the intensification of these winds and the movement of their average location towards the South Pole means that the ACC will also strengthen which will increase the upwelling of deeper warmer water. She says that the melting you report on the Antarctic Peninsula as well as growth of sea ice where its coldest in the Ross Sea are exactly what she expects to see if the ACC is… Read more »

Barry
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Barry

Doug: I assume this is primarily effecting shelf ice, which is small compared to the sheet itself. Not to minimize the situation in the least, but will greater shelf melt effect the rate of sheet advance or melt? What kind of volumes are we talking here and what kind of ocean level (MSL) change could we see in 10-20 years as result?

Doug Martinson
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Doug Martinson

David and Barry — First I want to thank you (and Jason previously) for your informed and thoughtful comments/questions. I am going to answer your questions/comments in context by giving a more detailed overview of my AGU presentation, which is briefly summarized in the report by science reporter Kevin Krajick. Obviously his summary left out unnecessary details, some of which directly speak to your questions, hence my approach of a more detailed summary. My talk was motivated by glaciological observations that the accelerated glacial melt in the Western Antarctic Ice Sheet (WAIS) is primarily a consequence of warmer ocean water… Read more »

Yoron
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Yoron

This is one of the most worrying studies I’ve read so far. How quickly does it change? It is accelerating as I presume? But in what way, smoothly, or do you find it able to ‘jump’?

Combine it with Hansen’s thoughts about the West Antarctica, and its geology, will it lead to the ice sheets able to ‘break of’?

And what about the under ice flows lubricating the inner of Antarctica? Will they too speed up? Or they won’t be affected?