It is graphs like this pair that make the global warming story so difficult to tell in the mainstream media:

2-02-2011 northernhemisphereanomalies

2-02-2011 southernhemisphereanomalies

The northern hemisphere fits in easily enough with the simple truth. Ice in the Arctic is declining at 3.5% per decade. It is the southern hemisphere that provided the ammunition for doubter Christopher Monckton when he wrote recently in The Australian. The quantity of sea ice has been increasing at 1.4% per decade.

Graham Readfearn had a go at rebutting Monckton statement that “a largely unreported gain in Antarctic sea ice since 1979 almost matches the widely reported loss of Arctic sea ice”. “Does it?” wrote Readfearn for the Crikey blog Rooted. “No, it doesn’t. The US National Snow and Ice Data Center states there has been a slight gain in Antarctic sea-ice cover of 0.9 per cent since 1979, the equivalent of about 100,000 sq km per decade. But the loss of ice in the Arctic over the same period is 500,000 sq km per decade.”

That’s true enough but perhaps more important – but less easy to illustrate in a non-technical way – is evidence that in the Antarctic the ice is being attacked from the bottom. In a paper presented recently to the American Geophysical Union in San Francisco, oceanographer Doug Martinson of the Lamont-Doherty Earth Observatory says new analyses of the heat content of the waters off Western Antarctic Peninsula are now showing a clear and exponential increase in warming waters undermining the sea ice, raising air temperatures, melting glaciers and wiping out entire penguin colonies.

“In the area I work there is the highest increase in temperatures of anywhere on Earth,” said Martinson to the Discovery News website. Martinson has been collecting ocean water heat content data for more than 18 years at Palmer Island, on the western side of the Antarctic Peninsula.

“Eighty-seven percent of the alpine glaciers are in retreat,” said Martinson of the Western Antarctic Peninsula. “Some of the Adele penguin colonies have already gone extinct.”

Martinson and his colleagues looked not only at their very detailed and mapped water heat data from the last two decades, but compared them with sketchier data from the past and deep ocean heat content measurements worldwide. All show the same rising trend that is being seen in Antarctica.

“When I saw that my jaw just dropped,” said Martinson. The most dramatic rise has happened since 1960, he said.

What the rising water heat means, he said, is that even if humanity got organized and soon stopped emitting greenhouse gases, there is already too much heat in the oceans to stop a lot of impacts — like the melting of a huge amount of Antarctic ice.

“There’s the potential that we’re locked into long term sea level rise for a long time,” Martinson told Discovery News. Martinson presented his latest ocean heat results on Monday at the meeting of the American Geophysical Union in San Francisco.

As for how fast the ice will melt and in what locations, that depends largely on whether the upwelling warm water comes in contact with the thick ice shelf that crowds the coast and holds the block the glaciers from reaching the sea.

That, in turn, depends on the winds which drive away the surface waters and make it possible for the deeper waters to rise to the surface, said senior researcher Robert Bindschadler of NASA’s Goddard Earth Science and Technology Center and the University of Maryland-Baltimore County.

“It can destroy the ice shelf if that heat can get to it,” said Bindschadler, who at the same meeting presented his work from the melting Pine Island Ice Shelf in Antarctica.

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Peter Fray
Peter Fray
Editor-in-chief of Crikey
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