Talk by Robert Bingham, University of Aberdeen – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > Activities 2013 > Talk by Robert Bingham...

Talk by Robert Bingham, University of Aberdeen

Inland thinning of West Antarctic Ice Sheet steered along subglacial rifts

Ice currently being liberated from the West Antarctic Ice Sheet (WAIS)
accounts for ~10% of observed global sea-level rise. Losses are
dominated by the accelerated draw-down and resultant “dynamic thinning”
of ice along the coastline, forced by oceanic or atmospheric
perturbations to the ice margin. Though key to improving projections of
future ice-sheet contributions to sea-level, the incorporation of
dynamic thinning into models has been restricted by lack of knowledge of
basal topography so that, for much of WAIS, the fundamental controls on
its dynamic losses, hence the rate and ultimate extent of its potential
retreat, remain difficult to quantify. Here I detail the discovery of a
subglacial trench up to 1.5 km deep and 20 km wide, connecting the
ice-sheet interior to the Bellingshausen margin, whose existence impacts
profoundly on current ice-dynamic losses. I report on use a suite of
ice-penetrating radar, magnetic and gravity measurements to interpret
the likely origins of the trench in rifting arising from crustal
thinning in association with the wider development of the West Antarctic
Rift System. Now deactivated, but exhumed by glacial erosion, the
inferred rift represents a conduit through which a palaeo-ice stream was
directed onto the continental shelf during glacial maxima, eroding the
major “Belgica” trough across Eltanin Bay which today routes warm
open-ocean water back to the ice front to reinforce dynamic thinning. I
show that the inland propagation of dynamic thinning from the
Bellingshausen margin is steered towards the ice-sheet interior directly
along the rift axis. Expanding analysis to the wider WAIS, it appears
that those basins that will most readily transmit coastally-perturbed
change inland are those underlain by old rifts that cut across the
modern ice-sheet margin.