Estimates of just how much the ice will melt and contribute to sea level rise are highly varied (Science Daily)

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http://www.sciencedaily.com/releases/2011/07/110728144727.htm

Sea Level Rise Less from Greenland, More from Antarctica, Than Expected During Last Interglacial

ScienceDaily (July 28, 2011) — During the last prolonged warm spell on Earth, the oceans were at least four meters — and possibly as much as 6.5 meters, or about 20 feet — higher than they are now.

Where did all that extra water come from? Mainly from melting ice sheets on Greenland and Antarctica, and many scientists, including University of Wisconsin-Madison geoscience assistant professor Anders Carlson, have expected that Greenland was the main culprit.

But Carlson’s new results, published July 29 in Science, are challenging that assertion, revealing surprising patterns of melting during the last interglacial period that suggest that Greenland’s ice may be more stable — and Antarctica’s less stable — than many thought.

“The Greenland Ice Sheet is melting faster and faster,” says Carlson, who is also a member of the Center for Climatic Research in the Nelson Institute for Environmental Studies. But despite clear observations of that fact, estimates of just how much the ice will melt and contribute to sea level rise by the end of this century are highly varied, ranging from a few centimeters to meters. “There’s a clear need to understand how it has behaved in the past, and how it has responded to warmer-than-present summers in the past.”

The ice-estimation business is rife with unknown variables and has few known physical constraints, Carlson explains, making ice sheet behavior — where they melt, how much, how quickly — the largest source of uncertainty in predicting sea level rises due to climate change.

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