Report

Fast retreat of Zachariæ Isstrøm, northeast Greenland

Science  11 Dec 2015:
Vol. 350, Issue 6266, pp. 1357-1361
DOI: 10.1126/science.aac7111

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Shrinking shelf and faster flow

Zachariæ Isstrøm, a large glacier in northeast Greenland, began a rapid retreat after detaching from a stabilizing sill in the late 1990s. Mouginot et al. report that between 2002 and 2014, the area covered by the glacier's ice shelf shrank by 95%; since 1999, the glacier's flow rate has nearly doubled; and its acceleration increased threefold in the fall of 2012. These dramatic changes appear to be the result of a combination of warmer air and ocean temperatures and the topography of the ocean floor at the head of the glacier. Rising sea levels should continue to destabilize the marine portion of Zachariæ Isstrøm for decades.

Science, this issue p. 1357

Abstract

After 8 years of decay of its ice shelf, Zachariæ Isstrøm, a major glacier of northeast Greenland that holds a 0.5-meter sea-level rise equivalent, entered a phase of accelerated retreat in fall 2012. The acceleration rate of its ice velocity tripled, melting of its residual ice shelf and thinning of its grounded portion doubled, and calving is now occurring at its grounding line. Warmer air and ocean temperatures have caused the glacier to detach from a stabilizing sill and retreat rapidly along a downward-sloping, marine-based bed. Its equal-ice-volume neighbor, Nioghalvfjerdsfjorden, is also melting rapidly but retreating slowly along an upward-sloping bed. The destabilization of this marine-based sector will increase sea-level rise from the Greenland Ice Sheet for decades to come.

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