Sunday, 18 December 2016

Ocean heat drives rapid basal melt of the Totten Ice Shelf

Source: "Ocean heat drives rapid basal melt of the Totten Ice Shelf", Science Advances, 16 Dec 2016, Vol. 2, no. 12, e1601610, DOI: 10.1126/sciadv.1601610

Authors

Stephen Rich Rintoul1,2,*, Alessandro Silvano2,3, Beatriz Pena-Molino1, Esmee van Wijk2, Mark Rosenberg1, Jamin Stevens Greenbaum4 and Donald D. Blankenship4

1Antarctic Climate and Ecosystems Cooperative Research Centre, University of Tasmania, Hobart, Tasmania, Australia.
2Commonwealth Scientific and Industrial Research Organization Oceans and Atmosphere, Hobart, Tasmania, Australia.
3Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.
4Institute for Geophysics, University of Texas at Austin, Austin, TX 78758, USA.
*Corresponding author. Email: steve.rintoul@csiro.au

Abstract

Mass loss from the West Antarctic ice shelves and glaciers has been linked to basal melt by ocean heat flux. The Totten Ice Shelf in East Antarctica, which buttresses a marine-based ice sheet with a volume equivalent to at least 3.5 m of global sea-level rise, also experiences rapid basal melt, but the role of ocean forcing was not known because of a lack of observations near the ice shelf. Observations from the Totten calving front confirm that (0.22 ± 0.07) × × 106 m3 s−1 of warm water enters the cavity through a newly discovered deep channel. The ocean heat transport into the cavity is sufficient to support the large basal melt rates inferred from glaciological observations. Change in ocean heat flux is a plausible physical mechanism to explain past and projected changes in this sector of the East Antarctic Ice Sheet and its contribution to sea level.

Introduction

Ice shelves form where the Antarctic Ice Sheet reaches the ocean and begins to float. Back stress produced by the interaction of the floating ice shelf with side walls and topographic rises buttresses the grounded ice sheet and inhibits the flow of ice into the ocean. The thinning or weakening of ice shelves reduces the back stress, increasing the discharge of grounded ice into the ocean and raising sea levels. The thinning of Antarctic ice shelves has been attributed to basal melt by ocean heat flux, with the most rapid thinning, grounding line retreat, and acceleration of glacial flow observed in the Bellingshausen Sea and the Amundsen Sea. Much of the ice sheet in that sector of Antarctica rests on bedrock below sea level that deepens upstream, a potentially unstable configuration that may result in rapid glacial retreat and mass loss to the ocean. Models and observations suggest that increased ocean heat flux may have already initiated the unstable retreat of some West Antarctic glaciers. Therefore, the future evolution of the Antarctic Ice Sheet is tightly linked to change in the surrounding ocean. (...)

Read more at: http://advances.sciencemag.org/content/2/12/e1601610.full

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