Geologists Drill into Antarctica and Find Troubling Signs for Ice Sheets' Future

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http://www.scientificamerican.com/article.cfm?id=antarctica-andrill-ice-sheets

April 19, 2010

Geologists Drill into Antarctica and Find Troubling Signs for Ice Sheets' Future

New sediment cores from an Antarctic research drilling program suggest that the southernmost continent has had a more dynamic history than previously suspected

By Clay Farris Naff

ERICE, Italy—If you think of http://www.scientificamerican.com/report.cfm?id=future-of-poles">Earth's poles as fraternal twins, http://www.scientificamerican.com/article.cfm?id=opening-of-northwest-passage">the Arctic has been the wild one in recent years, while the Antarctic has been a steady plodder. Withered by summer heat, Arctic sea ice has shrunk to record low coverage several times since 2005, only to rebound to within 95 percent of its long-term average extent this winter. By comparison, Antarctica, with some 90 percent of the world's glacial reserves, has generally shed ice in more stately fashion.

However, emerging evidence from an Antarctic geological research drilling program known as http://www.andrill.org/">ANDRILL suggests that the southernmost continent has had a much more dynamic history than previously suspected—one that could signal an abrupt shrinkage of its ice sheets at some unknown greenhouse gas threshold, possibly starting in this century. Especially troubling, scientists see evidence in the geological data that could mean the vast East Antarctic Ice Sheet, which holds at least four-fifths of the continent's ice, is less resistant to melting than previously thought.

ANDRILL, a collaboration among scientists from Germany, Italy, New Zealand and the U.S., obtained the evidence from a 3,734-foot-long core extracted in 2007 from the seafloor on the southern McMurdo Sound, near Antarctica's Ross Island.

A prior core, extracted from the McMurdo Ice Shelf between October 2006 and January 2007, indicated that the West Antarctic Ice Sheet has frequently advanced and retreated. As ANDRILL scientists met here April 6-11 to integrate core results, the geologists and climate modelers pondered the hints of dynamism observed in the much larger http://www.scientificamerican.com/article.cfm?id=antarctic-expedition-in-search-of-lost-mountains">East Antarctic Ice Sheet.

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