Impact of ocean forcing on the Aurora Basin in the 21st and 22nd centuries

S Sun,B K Galton-Fenzi,L Zhao,S L Cornford,D E Gwyther,R M Gladstone,J C Moore

doi:10.1017/aog.2016.27

S Sun, B K Galton-Fenzi + Show 5 more

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https://doi.org/10.1017/aog.2016.27

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Abstract

ABSTRACTThe grounded ice in the Totten and Dalton glaciers is an essential component of the buttressing for the marine-based Aurora basin, and hence their stability is important to the future rate of mass loss from East Antarctica. Totten and Vanderford glaciers are joined by a deep east-west running subglacial trench between the continental ice sheet and Law Dome, while a shallower trench links the Totten and Dalton glaciers. All three glaciers flow into the ocean close to the Antarctic circle and experience ocean-driven ice shelf melt rates comparable with the Amundsen Sea Embayment. We investigate this combination of trenches and ice shelves with the BISICLES adaptive mesh ice-sheet model and ocean-forcing melt rates derived from two global climate models. We find that ice shelf ablation at a rate comparable with the present day is sufficient to cause widespread grounding line retreat in an east-west direction across Totten and Dalton glaciers, with projected future warming causing faster retreat. Meanwhile, southward retreat is limited by the shallower ocean facing slopes between the coast and the bulk of the Aurora sub-glacial trench. However the two climate models produce completely different future ice shelf basal melt rates in this region: HadCM3 drives increasing sub-ice shelf melting to ~2150, while ECHAM5 shows little or no increase in sub-ice shelf melting under the two greenhouse gas forcing scenarios.

Highlights

Satellite observations show numerous regions of strong localized thinning along East Antarctica’s Sabrina Coast including the largest outlet of Aurora Basin, Totten Glacier (Pritchard and others, 2009; Flament and Rémy, 2012; Li and others, 2015)
A global ocean model indicates ice shelf basal melting will increase as the Southern Ocean warms in 21st and 22nd centuries (Timmermann and Hellmer, 2013), and at the same time widespread bedrock lying below sea level and deepening upstream from at least parts of the grounding line means that thinning of ice shelves renders the area potentially unstable through the marine ice-sheet instability (e.g. Moore and others, 2013)
We discuss the evolution of the Aurora Basins major outlets: Totten, Dalton and Vanderford glaciers, over the 21st century and 22nd century, and the impact of ocean warming and basal friction to this evolution

Summary

Introduction

Satellite observations show numerous regions of strong localized thinning along East Antarctica’s Sabrina Coast including the largest outlet of Aurora Basin, Totten Glacier (Pritchard and others, 2009; Flament and Rémy, 2012; Li and others, 2015). Each melt-rate formula is composed from a depth-dependent part based on a model of the present day, denoted by M, and a time-dependent part derived from emission driven climate projections, denoted by Ma. Present-day melt rates are parameterized based on an ocean model of the Totten ice shelf region (Gwyther and others, 2014), which was re-run with forcing conditions updated to cover the 1992–2012 period.

Results

Conclusion