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Slip, Slide, Shake

GPS, seismic data yield clues about surging Antarctic glacier

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1:10pm, June 4, 2008

Analyses of data gathered by Global Positioning System equipment atop one of Antarctica’s largest and most dynamic glaciers and by seismometers nearby suggest that friction in just one small area beneath the broad glacier regularly halts the ice’s lurching march to the sea.

Many of Antarctica’s largest ice streams — the megaglaciers that carry most of the ice draining off the continent — move at an irregular pace, first sticking in place, then surging ahead (SN: 3/31/07, p. 202). For instance, twice each day — at times related to the cycle of tides at the Antarctic coast — a large portion of the Whillans Ice Stream surges forward about 70 centimeters over the course of 25 minutes, says Matt King, a geophysicist at Newcastle University in England.

That may not sound impressive. But the total seismic energy triggered as this 200-kilometer-long, 100-kilometer-wide section of the ice stream scrap

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