Nature - Study Shows Laurentide Ice Sheet May Have Melted In Relatively Short 500, 800-Year Bursts

[hatrack]

The new study takes an alternative approach to using present-day records of changes in the ice sheet, instead garnering clues from the most recent known ice-sheet disappearance as an analogue for what could happen on Greenland. The results support other data that point to high rates of sea-level rise during previous interglacial periods3.

By piecing together paleoclimate records from the time of its retreat, the researchers determine that the Laurentide sheet, a vast expanse of ice that extended over most of Canada and the upper reaches of the United States between 7,000 and 20,000 years ago, may have melted rapidly over relatively short periods of 500 and 800 years. This melting would ultimately have contributed 0.7 to 1.3 metres of sea-level rise per century during those periods.

"We think that by about 7,000 years ago this ice sheet had disappeared, so we're talking about an exceptionally rapid disappearance of a very large ice sheet," says Allegra LeGrande, a postdoctoral fellow at the NASA Goddard Institute for Space Studies in New York and a co-author on the study.

The scientists used a combination of paleoclimatic techniques to calculate the rate of disappearance of the LIS. By analyzing radiocarbon dates of organic matter and marine shells, cosmogenic dates from the surface of boulders, and the composition of isotopes in marine sediment cores, they were able to decipher the chronology of past temperature changes and variations in the water cycle throughout the early Holocene, around 9,000 years ago, during which the ice sheet is thought to have vanished.

EDIT

http://www.nature.com/climate/2008/0809/full/climate.2008.88.html

[Systematic Chaos]

1. Then they're probably not expecting whole ice shelves to disappear in decades

at most.

:eyes: