Greenland and Antarctica hold the Earth’s last remaining ice sheets. In July, satellite data showed that 97 percent of the surface of the Greenland ice sheet had turned to slush over four days, a rate faster than at any time in recorded history. According to Carlson, it might be responding rapidly to small changes in temperature, similar to what he saw in the prehistoric record of ice sheets on land.
This marine-based glacier in the area of Greenland is retreating into land. (Photo: Kelsey Winsor/UW-Madison)
“But that said, they haven’t catastrophically collapsed in the past either to rapidly raise sea level in the time scale that humans would care about, that we would be hard pressed to adapt to.” Carlson says the Antarctic marine-based ice sheet is less predictable. “What this would say from the past is that these ice sheets, well they may not do anything for a bit. But then if you want to catastrophically raise sea level like on the orders of a meter or two in human lifetime, there is prehistoric precedent for that happening.”
A second paper in Nature Geoscience looks back 12,000 to 7,000 years to when massive ice sheets still covered the high latitudes of the Northern Hemisphere. At that time, the global climate was roughly comparable to what it is today and glaciers were melting.
Earth during the Ice Age 23,000 years ago with large ice sheets covering the Northern Hemisphere. (Credit: Anders Carlson)
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2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25