Friday, April 21, 2006

Glaciers melting faster than anticipated

A UW researcher has concluded Greenland's glaciers are melting up to twice as quickly as previously thought, suggesting scientists may have underestimated the impact of global warming.

If Greenland were to fully melt, it could raise sea levels as much as seven meters and permanently change ocean ecology and currents, said Ian Joughin, a senior engineer in the UW Polar Science Center.

Of concern to scientists is the acceleration of glaciers into the ocean and the increase in ice deposited, as well as the retreat of glaciers inland and their shrinking size. The results indicate that rising global temperatures have "a near immediate effect on glacier speeds," Joughlin wrote in a Science article last month.

In 1993, glaciers pushed approximately 30 gigatons of ice into the sea, where they later melted as icebergs. By 2005, iceberg production had doubled, with 60 gigatons of ice of being pushed into the arctic sea.

With so much more ice melting directly into the ocean, the rate at which the sea rises has increased about 20 percent.

Past estimates have shown that a three-degree increase in global temperature would melt all of Greenland in 1,000 years. But climate change models used to make those calculations relied solely on glacial melt while ignoring iceberg production. Taking into account iceberg production, a seven-meter rise in sea levels could happen much sooner, Joughin said.

The study of Greenland's glaciers can have even wider applications than predicting rises in sea levels, said Peter Rhines, a professor of oceanography and atmospheric sciences.

"Greenland can be seen as a gauge [for global warming]," he said. "[It] functions as a rabbit-hole effect on deep-sea ventilation."

Ocean climatology and biology is highly dependent on this ventilation, which only occurs in very few places in the world.

Even as researchers recognize the importance of global warming to glacial melt, in the end, Rhines said, "We're going to be surprised."

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