Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat, A. Jenkins et al., Nature Geosci., 3 (June 2010)

Nature Geoscience 3 (2010) 468-472; published online 20 June 2010; doi: 10.1038/ngeo890

Observations beneath Pine Island Glacier in West Antarctica and implications for its retreat

Adrian Jenkins^*,1, Pierre Dutrieux¹, Stanley S. Jacobs², Stephen D. McPhail³, James R. Perrett³, Andrew T. Webb³ and David White³

Abstract

Thinning ice in West Antarctica, resulting from acceleration in the flow of outlet glaciers, is at present contributing about 10% of the observed rise in global sea level¹. Pine Island Glacier in particular has shown nearly continuous acceleration^{2, 3} and thinning^{4, 5}, throughout the short observational record. The floating ice shelf that forms where the glacier reaches the coast has been thinning rapidly⁶, driven by changes in ocean heat transport beneath it. As a result, the line that separates grounded and floating ice has retreated inland⁷. These events have been postulated as the cause for the inland thinning and acceleration^{8, 9}. Here we report evidence gathered by an autonomous underwater vehicle operating beneath the ice shelf that Pine Island Glacier was recently grounded on a transverse ridge in the sea floor. Warm sea water now flows through a widening gap above the submarine ridge, rapidly melting the thick ice of the newly formed upstream half of the ice shelf. The present evolution of Pine Island Glacier is thus part of a longer-term trend that has moved the downstream limit of grounded ice inland by 30 km, into water that is 300 m deeper than over the ridge crest. The pace and ultimate extent of such potentially unstable retreat¹⁰ are central to the debate over the possibility of widespread ice-sheet collapse triggered by climate change^{11, 12}.

1. British Antarctic Survey, Natural Environment Research Council, Cambridge CB3 0ET, UK
2. Lamont-Doherty Earth Observatory of Columbia University, New York, New York 10964, USA
3. National Oceanography Centre, Southampton SO14 3ZH, UK

*Correspondence e-mail: ajen@bas.ac.uk

Link:  http://www.nature.com/ngeo/journal/v3/n7/abs/ngeo890.html

Comment from glacierchange:

This is an excellent ongoing study that will yield more results in the near future particularly when combined with the surface observations of NASA's Operation Ice Bridge. A few PIG figures from the early work indicate the problem of the grounding line retreat.