Wednesday, January 16, 2008

Southern Melt

Recent data shows that melting of the West Antarctic Ice shelf is now proceeding at faster than predicted rates. The significance of this may be obvious to those watching global climate change but for climate change deniers undermines (literally) a premise that global warming does not affect the South Pole. Specifically the minimal temperature change at the Southern latitudes is not reflected in air temperature change. Now significant data suggests that ocean warming is melting Antarctic ice from below:

"In an e-mail, Dr. Rignot attributed the shrinkage in the ice sheet to an upwelling of warm waters along the Antarctic coast, which is causing some glaciers to flow more rapidly into the ocean.

He suspects the trend is due to global warming, and isn't part of a normal natural fluctuation.

"I see that as the main driver for the change in ice mass. And this means that we are not in a natural cycle, but in something that is related to global warming or global climate change, whichever you want to call it," he said.

The study said the continent had a net loss of about 196 billion tonnes of ice in 2006, an amount that is equal to more than a third of the water in Lake Erie, up from 112 billion tonnes in 1996.

The figures were calculated by deducting the amount of ice losses on the continent from the amount of snow that computer models indicate it receives.

The figures were based on satellite data on ice thickness and the speeds at which glaciers are flowing into the ocean.

Dr. Rignot said the Antarctic ice loss in 2006 raised sea levels about half a millimetre, putting it on par with the contribution to sea level rise from the recently observed melting of the Greenland ice sheet.

Within scientific circles, there is little doubt that Greenland's ice is melting, but there has been more uncertainty over the fate of the larger stores of ice on Antarctica.

The Intergovernmental Panel on Climate Change, the UN-sponsored scientific body that compiles information on global warming, said last year that studies on the subject have been all over the map.

Some have suggested the ice cap was expanding by 50 billion tonnes a year from 1993 to 2003, while others projected losses over the same period of up to 200 billion tonnes.

It said the wide range of estimates reflected such factors as the small number of ice measurements made on the continent and disagreements among scientists on what techniques best estimate trends there.

Some experts have even speculated that global warming might lead to increases in ice accumulation in Antarctic's interior due to more snowfall.

However, many experts say that this effect is unlikely to offset Antarctica's contribution to sea level rise because of the rapid melting of coastal glaciers.

"The concept that global warming will increase precipitation in Antarctica and mitigate sea level rise is a lullaby," Dr. Rignot said.

"Our [study] shows that the main driver for the mass balance is the rate of glacier flow to the sea, not the precipitation rate because other studies already showed recently that the precipitation rate has not changed significantly."

Another member of the research team, Curt Davis, director of the Centre for Geospatial Intelligence at the University of Missouri-Columbia, said the new study is the "most comprehensive" to date on the status of Antarctica's ice, and has zeroed in on exactly where the losses are occurring.

It found that the biggest losses are in West Antarctica, around the Amundsen Sea, and in the Antarctic Peninsula, the continent's distinctive long arm of land that points like a finger up at South America.

One encouraging finding from the study is that the largest ice sheet, the one covering East Antarctica, has remained relatively stable, showing a small net gain in size."

Meanwhile America fiddles while the world melts. I don't see any evidence that American voters are being presented with anyone with serious energy or climate concerns.

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