From: Kieran Mulvaney, Discovery News
Published September 15, 2012 08:25 AM

Ice Sheets Apparently Can Grow Quickly in Cold Periods

How fast can glaciers and ice sheets expand and shrink in response to rapidly changing climatic conditions? It's a question that scientists have been pondering with particular interest of late, with Greenland's Peterman Glacier calving large amounts of ice two years in succession, and much of the island's surface ice melting earlier this summer.


Because abrupt climate changes have occurred, across various spatial and temporal scales, at several previous points in the planet's history, scientists can look for prehistorical clues, to see what happened then and thus infer what might happen in a warming 21st century. A team of geologists has done just that, although it has looked for evidence not during previous warm spells, but by looking at two major cooling events in Earth's past.

One, called the Younger Dryas period, began about 13,000 years ago and lasted more than a millennium. A second, less prosaically dubbed the 8.2 kiloyear event (because it occurred approximately 8,200 years ago), was less intense and was far shorter in duration - no more than 150 or so years. In this week's journal Science, Nicolas Young of Columbia University and colleagues write that, by dating moraines - piles of rocks and debris that glaciers deposit while expanding - on Canada's Baffin Island, they found that glaciers had been significantly more expansive during those cold periods.

No surprise there, of course. What was interesting and seemingly counter-intuitive, however, was that those glaciers appeared to cover a larger area during the more recent, shorter-lived, and less intense cold spell than during the Younger Dryas period.

Ice Sheet image via Shutterstock.

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