Deep Ocean Heat Is Melting Antarctic Ice
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 2010 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. (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.
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