Map tracks Antarctica on the move
Baku, August 20 (AZERTAC). Scientists have produced what they say is the first complete map of how the ice moves across Antarctica.
Built from images acquired by radar satellites, the visualisation details all the great glaciers and the smaller ice streams that feed them.
The map has been published online by Science magazine.
It should aid the understanding of how the White Continent might evolve in the warmer world being forecast by climatologists.
"This is like seeing a map of all the oceans` currents for the first time. It`s a game changer for glaciology," said lead author Dr Eric Rignot.
"We are seeing amazing flows from the heart of the continent that had never been described before," added the US space agency (Nasa) and University of California (UC), Irvine, researcher.
The map incorporates billions of radar data points collected between 1996 and 2009 by satellites belonging to Europe, Canada and Japan.
It closes previous data omissions, especially in the east of the continent.
Dr Drinkwater praised in particular the contribution of Canadian company MacDonald, Dettwiler and Associates, which rolled its Radarsat-2 spacecraft every time it flew near the pole to get a view of the ice surface at the highest latitudes. "That was the only way we could fill the so-called `data hole` that satellites traditionally don`t see," he explained.
Ice movement is detected using a technique called Satellite Radar Interferometry (InSAR), which compares images from repeat passes over the same location.
InSAR will pick up even subtle deformations in the ice sheet resulting from slow creep. That said, some areas of Antarctica are moving very fast.
Ice velocities on the new map range from just few cm/year near places where the ice divides into different paths, to km/year on fast-moving glaciers and the ice shelves that float out from the edges of the continent.
The sprinters are Pine Island and Thwaites glaciers in West Antarctica. This region, say the authors, is also the part of the continent "experiencing most rapid change at present, over the widest area, and with the greatest impact on total ice sheet mass balance".
Recent survey work has revealed that Pine Island, for example, is thinning rapidly; its surface has been dropping by more than 15m per year.
Other fast-moving streams include the Larsen B glaciers on the Antarctic Peninsula. These glaciers experienced an eightfold increase in speed when the floating ice shelf that bounded them collapsed in 2002.
Although the broad picture of how the ice drains from the centre of Antarctica to the edges has been reasonably well characterised for some time, the map throws up a number of previously unrecognised features. These include a new ridge that splits the 14 million square km landmass from east to west.
The map will be useful in monitoring change over time, by comparing it to past and future measurements.
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