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SUMMARY:Inland thinning of West Antarctic Ice Sheet steered along subglaci
 al rifts - Dr Rob Bingham\, University of Aberdeen
DTSTART:20120229T163000Z
DTEND:20120229T173000Z
UID:TALK34000@talks.cam.ac.uk
CONTACT:Steven Palmer
DESCRIPTION:Ice currently being liberated from the West Antarctic Ice Shee
 t (WAIS) accounts for ~10% of observed global sea-level rise. Losses are d
 ominated by the accelerated draw-down and resultant “dynamic thinning”
  of ice along the coastline\, forced by oceanic or atmospheric perturbatio
 ns to the ice margin. Though key to improving projections of future ice-sh
 eet contributions to sea-level\, the incorporation of dynamic thinning int
 o models has been restricted by lack of knowledge of basal topography so t
 hat\, for much of WAIS\, the fundamental controls on its dynamic losses\, 
 hence the rate and ultimate extent of its potential retreat\, remain diffi
 cult 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 Bel
 lingshausen margin\, whose existence impacts profoundly on current ice-dyn
 amic losses. I report on use a suite of ice-penetrating radar\, magnetic a
 nd gravity measurements to interpret the likely origins of the trench in r
 ifting arising from crustal thinning in association with the wider develop
 ment of the West Antarctic Rift System. Now deactivated\, but exhumed by g
 lacial erosion\, the inferred rift represents a conduit through which a pa
 laeo-ice stream was directed onto the continental shelf during glacial max
 ima\, eroding the major “Belgica” trough across Eltanin Bay which toda
 y 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 a
 long the rift axis. Expanding analysis to the wider WAIS\, it appears that
  those basins that will most readily transmit coastally-perturbed change i
 nland are those underlain by old rifts that cut across the modern ice-shee
 t margin.
LOCATION:Scott Polar Research Institute\, main lecture theatre
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