Report

Regular Patterns in Frictional Resistance of Ice-Stream Beds Seen by Surface Data Inversion

Science  29 Nov 2013:
Vol. 342, Issue 6162, pp. 1086-1089
DOI: 10.1126/science.1243903

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Banding Together

It is important to understand how and where the Antarctic Ice Sheet and underlying ground are coupled, if we want to predict the glacial contribution to sea level rise. Sergienko and Hindmarsh (p. 1086, published online 7 November) used observations of ice surface velocities, ice surface elevations, and bed elevations to perform inverse calculations of basal shear stress. Areas of high basal stress were distributed in riblike patterns embedded in much larger areas of no basal shear stress, which may affect the rates at which ice is discharged into the ocean.

Abstract

Fast-flowing glaciers and ice streams are pathways for ice discharge from the interior of the Antarctic Ice Sheet to ice shelves, at rates controlled by conditions at the ice-bed interface. Using recently compiled high-resolution data sets and a standard inverse method, we computed basal shear stress distributions beneath Pine Island and Thwaites Glaciers, which are currently losing mass at an accelerating rate. The inversions reveal the presence of riblike patterns of very high basal shear stress embedded within much larger areas with zero basal shear stress. Their colocation with highs in the gradient of hydraulic potential suggests that subglacial water may control the evolution of these high–shear-stress ribs, potentially causing migration of the grounding line by changes in basal resistance in its vicinity.

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