Aug 21, 2008
WASHINGTON (AFP) — Two of Greenland's largest glaciers lost more ice to global warming over the last month, US researchers said Thursday. Glaciologists at the Byrd Polar Research Center at Ohio State University observed the break-ups by monitoring daily NASA satellites images as well as time-lapse photography from cameras monitoring Greenland's glaciers.

A huge chunk of the Petermann Glacier measuring 29 square kilometers (11 square miles) -- roughly half the size of Manhattan -- broke away between July 10 and 24, said Jason Box, a professor of geography at Ohio State University. Petermann, in northern Greenland, last lost a major mass of ice -- 86 square kilometers (33 square miles) -- between 2000 and 2001.

More worrisome, Box said, is an enormous crack further back from the margin of the Petermann Glacier that could signal "an imminent and much larger breakup." "If the Petermann Glacier breaks up back to the upstream rift, the loss would be as much as 60 square miles (160 square kilometers)," or one-third of the massive ice field, Box said.

The scientists also said that the margin of the massive Jakobshavn glacier has retreated inland further than at any time in the past 150 years of observation. They believe, moreover, that it has not retreated so far inland "in at least the last 4,000 to 6,000 years." Jakobshavn's northern branch has broken up in the last several weeks and the glacier has lost at least 10 square kilometers (three square miles) since the end of the last melt season, the researchers said.

About one-tenth of Greenland's icebergs come from Jakobshavn, making it the island's most productive glacier. The glacier lost 94 square kilometers (36 square miles) of ice field betwen 2001 and 2005, a phenomenon that drew international attention to the impact of global warming on glaciers, the scientists said.

Meanwhile, the roof of an ice tunnel in Argentina's gigantic Perito Morena glacier, 60 meters high and weighing thousands of tonnes, suddenly collapsed July 8, a phenomenon unheard of in the dead of the southern hemisphere winter. Scientists blamed global warming for the collapse.

From: http://afp.google.com/article/ALeqM5j85xiiOkJJIaNZtMD8e7ceZC9E3Q