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Abstract |
The ice streams of the George V Coast drain from the large Wilkes Subglacial Basin behind East Antarctica's Transantarctic Mountains, into fragmentary ice shelves exposed to the Southern Ocean. As part of NASA's Operation Ice Bridge, the ICECAP program has been conducting integrated aerogeophysical observations over these glaciers, targeting Mertz Glacier, Ninnis Glacier and the glaciers feeding Cook Ice Shelf, using the resources of the French Polar Institute. Our instrument suite included multifrequency radar, gravimetry, magnetics and the ALAMO (Airborne Laser Altimetry with Mapping Optics) hybrid laser/lidar altimeter system. A primary objective of these observations is to extend and improved the 2003-2009 surface elevation record of GLAS (Geoscience Laser Altimeter System) instrument onboard NASA's ICESat satellite. We can improve on the GLAS only record as small pointing errors in GLAS lead to measurements that deviate from the nominal track by several hundred meters. In areas of high slope, this confounds elevation change due to surface slope with the dH/dt signal. With accurate surface slopes, the impacts of these two effects can be separated. This is particularly important in the coastal ice streams, which have both rapidly changing elevations and high surface slopes. Here we report on a combined ALAMO-GLAS slope corrected surface elevation record for Cook Ice Shelf, and find clear evidence for ice surface lowering over the deep trench that defines fast ice flow in this ice catchment. |
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