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SUMMARY:Predicting subglacial lake locations and meltwater drainage pathwa
 ys in Antarctica\, Greenland and North America  - Stephen J. Livingstone (
 University of Sheffield)
DTSTART:20131016T153000Z
DTEND:20131016T163000Z
UID:TALK47527@talks.cam.ac.uk
CONTACT:Poul Christoffersen
DESCRIPTION:There is increasing recognition that subglacial lakes act as k
 ey components within the ice sheet system\, capable of influencing ice-she
 et topography\, ice volume and ice flow. At present\, much glaciological r
 esearch is concerned with the role of modern subglacial lake systems in An
 tarctica. Another approach to the exploration of subglacial lakes involves
  identification of the geological record of subglacial lakes that once exi
 sted beneath ice sheets of the last glaciation. Investigation of such pala
 eo-subglacial lakes offers significant advantages because we have comprehe
 nsive information about the bed properties\, they are much more accessible
  and we can examine and sample the sediments with ease. However\, their id
 entification in the geological record remains controversial. \n\nWe theref
 ore present a simple diagnostic approach based on the Shreve equation\, fo
 r predicting and investigating likely (palaeo-)subglacial lake locations. 
 Data on the current topography and seafloor bathymetry\, and elevation mod
 els of the ice and ground surface topography from data-calibrated glaciolo
 gical modelling are used to calculate the hydraulic potential surface at t
 he ice-sheet bed. Meltwater routing algorithms and the flooding of local h
 ydraulic minima allow us to predict subglacial routeways and lakes respect
 ively. \n\nDiscovered subglacial lakes beneath the Antarctic Ice Sheet pre
 sent an opportunity to verify the model using the BEDMAP2 dataset. Using a
  lake threshold of 5 km2 we identify 12\,767 subglacial lakes occurring ov
 er 4% of the grounded bed and are able to recover >60% of the discovered s
 ubglacial lakes. Applying the same approach to the Greenland Ice Sheet pro
 duces 1\,607 potential subglacial lakes\, covering 1.3% of the bed. These 
 lake localities will make suitable targets for radar surveys attempting to
  find subglacial lakes. \n\nFinally\, we apply the Shreve equation to the 
 North American Ice Sheet to try and predict likely palaeo-subglacial lake 
 locations. Given that specific ice surface elevations of the former North 
 American Ice Sheet are only inferred from modelling\, and thus contain sig
 nificant uncertainty\, we utilise results from an ensemble of models to ex
 amine where on the bed subglacial lakes are likely to have occurred. Predi
 ctions are calculated at discrete time-slices through deglaciation to asse
 ss the temporal variability and persistence of subglacial lakes and draina
 ge networks. These lake likelihood predictions could usefully form targets
  for detailed field investigations.\n
LOCATION:Scott Polar Research Institute\, main lecture theatre
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