Universe Today
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A huge ice island four times the size of Manhattan-- and half as thick as the Empire State Building is tall-- has broken off from one of Greenland's two main glaciers. On August 5, 2010, an enormous chunk of ice, roughly 97 square miles (251 square kilometers) in size, broke off the Petermann Glacier, along the northwestern coast of Greenland. Satellite images, like this one from NASA's Aqua satellite show the glacier lost about one-quarter of its 70-kilometer (40-mile) long floating ice shelf. Located a thousand kilometers south of the North Pole, the now-separate ice island contains enough fresh water to keep public tap water in the United States flowing for 120 days, said scientists from the University of Delaware who have been monitoring the break.
While thousands of icebergs detach from Greenland's glaciers every year, the last time one this large formed was in 1962. The flow of sea water beneath Greenland's glaciers is a main cause of ice detaching from them.
This movie made from another satellite -- Envisat from the European Space Agency – shows the giant iceberg breaking off.
[caption id="" align="alignnone" width="400" caption="Time-series animation based on Envisat Advanced Synthetic Aperture Radar (ASAR) data from 31 July, 4 August, and 7 August 2010 showing the breaking of the Petermann glacier and the movement of the new iceberg towards Nares Strait. Credits: ESA"]
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The animation above was created by combining three Advanced Synthetic Aperture Radar (ASAR) acquisitions (31 July, 4 August and 7 August 2010) taken over the same area. The breaking of the glacier tongue and the movement of the iceberg can be clearly seen in this sequence.
The Petermann glacier is one of the largest glaciers connecting the Greenland inland ice sheet with the Arctic Ocean. Upon reaching the sea, a number of these large outlet glaciers extend into the water with a floating 'ice tongue'. The ice tongue of the Petermann glacier was the largest in Greenland. This tide-water glacier regularly advances towards the ocean at about 1 km per year. During the previous months, satellite images revealed that several cracks had appeared on the glacier surface, suggesting to scientists that a break-up event was imminent.
Scientists say it's hard to tell if global warming caused the event. Records on the glacier and sea water below have only been kept since 2003. The first six months of 2010 have been the hottest globally on record.
Sources:
NASA,
ESA
