Antarctic: Giant iceberg breaks off glacier

A ice shelf piece as big as Hamburg has been released from the Pine Island Glacier

On the left side of the photo you can see the newly formed iceberg with a size of 720 square kilometers. © DLR
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On Monday, on the Antarctic Pine Island Glacier, a huge area of ​​ice shelves has broken loose. The iceberg is 720 square kilometers in size and thus has almost the surface of the city of Hamburg. The glacier is one of the longest and fastest flowing glaciers in the Antarctic. On the
Earth observation satellites TerraSAR-X researchers have followed the ice break and documented in single shots. However, climate change should not be responsible for this event - or at least not directly - according to the researchers.

The first crack in the tongue of the Pine Island glacier NASA scientists had already discovered on 14 October 2011 in an overflight. He was then about 24 kilometers long and 50 meters wide. Since then, researchers observed the progression of the crack and the formation of a second, including high-resolution radar images of the Earth observation satellite TerraSAR -X of the German Aerospace Center (DLR). Among other things, the researchers measured the gap widths and calculated the flow velocity of the ice.

"Above the great rift, the glacier last flowed at a speed of twelve meters per day, " says Dana Floricioiu from DLR. On the basis of the images, the researchers were able to follow how the larger rift on the Pine Island glacier initially extended to a distance of 28 kilometers. Shortly before the "birth" of the iceberg, the gap then opened piece by piece, so that it measured at its widest point about 540 meters. On July 8, 2013, it was finally time: "As a result of the cracks, a huge iceberg has detached from the glacier tongue - it measures 720 square kilometers and is almost as large as the city of Hamburg, " says Angelika Humbert, ice researcher Alfred-Wegener Institute for Polar and Marine Research.

Aerial view of the Pine Island Glacier Angelika Humbert / Alfred Wegener Institute

Is climate change to blame?

Are ice breaks like this caused by climate change? Humbert does not yet see a direct connection: "The formation of cracks in the ice shelf and thus the formation of new icebergs are natural processes, " says the glaciologist. However, the Pine Island Glacier, which flows from the Hudson Mountains into the Amundsen Sea, is the fastest-flowing glacier in the western Antarctic at a speed of around four kilometers per year.

However, this speed is less caused by rising air temperatures. Rather, it is based on the fact that the wind directions in the Amundsen See have changed. The wind now brings warm sea water under the ice shelf. Over time, this process causes the ice shelf to melt from below, especially at the so-called touchdown line, the critical transition to the inland ice, says the scientist. display

For the West Antarctic ice sheet, even faster flowing of the Pine Island glacier would probably have serious consequences: The West Antarctic ice sheet lies on land lower than the sea level. His "bed" also tilts inland. So there is a real danger that these large ice sheets will become unstable and slip, "says Humbert. If the entire West Antarctic ice sheet were to flow into the ocean, this would result in a global sea level rise of approximately 3.3 meters.

Events like this provide the scientists with a good opportunity to compare their models of ice dynamics with observations. If model calculation and reality agree, the scientists can for example conclude which gliding property the soil under the glacier ice possesses or how the ice flow might behave in the event of further global warming. Glacier are constantly on the move. They have their own fluid dynamics. Their ice is exposed to permanent tensions and the calving of icebergs is still largely unexplored, says Humbert.

(Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, 10.07.2013 - NPO)