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Abstract:
When an ice shelf collapses, the removal of its backstress acting on the tributary glaciers results in increased flow speed, decreased surface elevation and decreasing ice thickness. Rises in surface slope gradients further drive an increase in flow speeds. Over February to March of 2002, the Larsen B Ice Shelf, in the northwestern Antarctic Peninsula, disintegrated, leading to its largest contributing glacier, Crane Glacier, to double in ice discharge and decrease in elevation by over 100 m from ~2003-2009. One parameter of Crane Glacier, its grounding line position, has never been documented and the effects of the external forces acting on grounding line dynamics have never been quantified. The exact position of the grounding line in 2002 is not well known, but by using multi-temporal geophysical datasets (e.g., digital elevation models, airborne radar; 1968-2022) the down-flow margin of the grounding zone—hydrostatic equilibrium boundary—can be estimated. The historical hydrostatic equilibrium boundaries are calculated using trimetrogon aerial imagery to produce orthometric elevations from 55 years ago using structure-from-motion photogrammetry. We assume that fluctuations in the location of the floatation limit directly reflects the migration of the grounding line. Analysis of Crane Glacier’s grounding line dynamics before and after the 2002 ice shelf break up offers a unique opportunity to better understand the stability of the Antarctic’s major ice-shelf-terminating outlet glaciers.
