Monday, January 14, 2008

Antarctic melt

By Michael J.W. Stickings

The Antarctic ice sheet, which covers about 98 percent of Antarctica, contains about 90 percent of the world's total ice mass and about 61 percent of the world's total fresh water. It is estimated that global sea levels would rise about 60 meters were it to melt completely.

And it is melting. And melting quickly, according to an important new study:


One of the biggest worries about global warming has been its potential to affect the stability of the Antarctic ice sheet, a vast storehouse of frozen water that would inundate the world's coastal regions if it were to melt because of a warming climate.

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[A] new study released [yesterday], based on some of the most extensive measurements to date of the continent's ice mass, presents a worrisome development: Antarctica's ice sheet is shrinking, at a rate that increased dramatically from 1996 to 2006.

"Over the time period of our survey, the ice sheet as a whole was certainly losing mass, and the mass loss increased by 75 per cent in 10 years," the study said.


The study was conducted by the Radar Science and Engineering Section of NASA's Jet Propulsion Laboratory. One of the scientists involved in the study, Dr. Eric Rignot, offered this explanation: "I see [global warming] 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."

There has been some disagreement in scientific circles with respect to the Antarctic ice sheet. While there is broad agreement that the Greenland ice sheet is melting, "there has been more uncertainty over the fate of the larger stores of ice on Antarctica," with some researchers suggesting that increased precipitation could actually increase the size of the ice sheet over time. This new study offers evidence against that. Dr. Rignot: "The concept that global warming will increase precipitation in Antarctica and mitigate sea level rise is a lullaby. Our story 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."

In other words, the results of this study show that the Antarctic ice sheet is melting and that the rate of melting has increased in recent years. A consensus could emerge around these findings, a consensus that could focus greater attention not just on the effects of global warming on Antarctica but on efforts to combat global warming generally. The possibility of a significant, and devastating, rise in global sea levels, backed up by solid and essentially incontrovertible evidence resulting from extensive scientific research, should be enough to stimulate broad-based action. The problem is, it may not matter what the scientists say or recommend. Even if personal and political ignorance and negligence can ever be overcome to the extent that effective action can be taken, the will to act may come too late to hold off what is increasingly looking like the inevitable.

Still, this seems to have been a worthwhile and exceptionally valuable study. If nothing else, it tells us that the situation is even bleaker than we had previously thought.

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Update: For more, see WaPo.

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