Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith, and Kohler glaciers, West Antarctica, from 1992 to 2011

E Rignot,B Scheuchl,M Morlighem,H Seroussi,J Mouginot

doi:10.1002/2014gl060140

E Rignot, B Scheuchl + Show 3 more

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https://doi.org/10.1002/2014gl060140

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Abstract

AbstractWe measure the grounding line retreat of glaciers draining the Amundsen Sea sector of West Antarctica using Earth Remote Sensing (ERS‐1/2) satellite radar interferometry from 1992 to 2011. Pine Island Glacier retreated 31 km at its center, with most retreat in 2005–2009 when the glacier ungrounded from its ice plain. Thwaites Glacier retreated 14 km along its fast flow core and 1 to 9 km along the sides. Haynes Glacier retreated 10 km along its flanks. Smith/Kohler glaciers retreated the most, 35 km along its ice plain, and its ice shelf pinning points are vanishing. These rapid retreats proceed along regions of retrograde bed elevation mapped at a high spatial resolution using a mass conservation technique that removes residual ambiguities from prior mappings. Upstream of the 2011 grounding line positions, we find no major bed obstacle that would prevent the glaciers from further retreat and draw down the entire basin.

Highlights

The grounding line is the critical boundary between grounded ice and the ocean which delineates where ice detaches from the bed and becomes afloat and frictionless at its base
The 1996 ice velocity (Figure 1) provides a visual reference for comparing the grounding line retreat with flow speed, because changes in flow speed are largest in fast-moving areas [Mouginot et al, 2014], which thin the most and are most conducive to ice ungrounding
We have no 2011 data on the stream merging into the ice shelf from the west at point K, but we detect no migration in 1992–2000

Summary

Introduction

The grounding line is the critical boundary between grounded ice and the ocean which delineates where ice detaches from the bed and becomes afloat and frictionless at its base. Its position is mapped accurately (millimeter of vertical motion), at a high spatial resolution (< 50 m), simultaneously and uniquely over large areas using satellite radar interferometry (interferometric synthetic aperture radar (InSAR)) [Rignot et al, 2011] Knowledge of this position is critical for mass flux calculation and mass budget assessment [e.g., Rignot et al, 2008], ice sheet numerical modeling [e.g., Larour et al, 2012; Gillet-Chaulet and Durand, 2010], analysis of ice shelf melting [Rignot et al, 2013], and evaluation of glacier/ice shelf stability [Thomas et al, 2004a, 2004b]. The AS is a dominant contributor to the mass loss from the Antarctic ice sheet at present, with losses driven almost entirely by increases in flow speed [Mouginot et al, 2014] This sector is of global significance since it contains enough ice to raise global sea level by 1.2 m [e.g., Rignot, 2008]

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