The imbalance of glaciers after disintegration of Larsen-B ice shelf, Antarctic Peninsula

摘要

The outlet glaciers to the embayment of the Larsen-B Ice Shelf started toaccelerate soon after the ice shelf disintegrated in March 2002. We analysehigh resolution radar images of the TerraSAR-X satellite, launched in June2007, to map the motion of outlet glaciers in detail. The frontal velocitiesare used to estimate the calving fluxes for 2008/2009. As reference forpre-collapse conditions, when the glaciers were in balanced state, the icefluxes through the same gates are computed using ice motion maps derivedfrom interferometric data of the ERS-1/ERS-2 satellites in 1995 and 1999.Profiles of satellite laser altimetry from ICESat, crossing the terminus ofseveral glaciers, indicate considerable glacier thinning between 2003 and2007/2008. This is taken into account for defining the calving crosssections. The difference between the pre- and post-collapse fluxes providesan estimate on the mass imbalance. For the Larsen-B embayment the 2008 massdeficit is estimated at 4.34 ± 1.64 Gt a?1, significantly lowerthan previously published values. The ice flow acceleration follows asimilar pattern on the various glaciers, gradually decreasing in magnitudewith distance upstream from the calving front. This suggests stressperturbation at the glacier front being the main factor for acceleration. Sofar there are no signs of slow-down indicating that dynamic thinning andfrontal retreat will go on.