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article imagePetermann Glacier's new cracks indicate possible calving event

By Karen Graham     Feb 8, 2019 in Science
Cracks in the floating ice tongue of Petermann Glacier in the far northwest reaches of Greenland indicate the pending loss of another large iceberg.
Petermann Glacier is one of Greenland's largest glaciers. In 2012, a "tongue" of ice broke off - releasing an iceberg about the size of Manhattan. Dubbed PII-2012, the giant iceberg measured approximately 46 square miles (120 square kilometers) in size.
Since that time, the glacier's slow but steady forward movement has been accelerating, with the flow rate increased by an average of 10 percent, report glaciologists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).
According to the researchers, the widening cracks in the glacier's tongue indicate a pending loss of a large section of ice that could have a corresponding effect on sea levels. The research was published in the Journal of Geophysical Research: Earth Surface,
July 13  2014: Landsat 8 (path/row 45/1) — Petermann Glacier  Greenland
July 13, 2014: Landsat 8 (path/row 45/1) — Petermann Glacier, Greenland
US Geological Survey
Petermann Glacier covers close to 500 square miles (1,295 square kilometers) in northwestern Greenland and is one of only three glaciers in Greenland that has an icy "tongue." It sort of lolls across the fiords and into the North Sea.
Measuring 9 to 12 miles (15 to 20 kilometers) wide and approximately 44 miles (70 kilometers) long, Petermann's tongue makes it the longest floating glacier in the Northern Hemisphere, according to the U.S. Geological Survey (USGS).
Left: ASTER ( satellite scene acquired shortly after the 2012 calving...
Left: ASTER ( satellite scene acquired shortly after the 2012 calving event on 2012/07/21. Right: Sentinel-2 ( acquisition on 2018/07/31 indicating newly developing fractures in the terminus region.
ASTER; Sentinel-2
The new cracks are about 8 miles (12 kilometers) from the new edge of the tongue. While the computer models showed the speedup of the glacier after the 2012 calving event, the models also indicate an even further acceleration in the speed of the flow if another iceberg breaks off.
The resulting ice loss could cause sea levels to rise. According to lead study author and AWI ice modeler Martin Rückamp, "We can't predict when Petermann Glacier will calve again, or whether a calving event would actually calve along the cracks we identified in the ice tongue. But we can safely assume that, if it does come to a new calving event, the tongue will retreat considerably, and the rock's stabilizing effect will further decline."
More about Greenland, Petermann glacier, new cracks, calving event, Ice storm
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