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SUMMARY:Geophysical surveys of Subglacial Lake Ellsworth\, West Antarctica
 : implications for in-situ exploration - John Woodward\, Northumbria Unive
 rsity
DTSTART:20090304T163000Z
DTEND:20090304T173000Z
UID:TALK17274@talks.cam.ac.uk
CONTACT:Poul Christoffersen
DESCRIPTION:In addition to exerting a significant impact on ice sheet dyna
 mics\, subglacial lakes are expected to contain unique life forms and reco
 rds of ice sheet history. To date\, none of the ~150 Antarctic lakes disco
 vered from radio echo sounding surveys have been accessed directly. The El
 lsworth Consortium has recently received funding to access Subglacial Lake
  Ellsworth (SLE) in West Antarctica in 2012/13. In order to plan for lake 
 access we have completed a geophysical reconnaissance of SLE. A series of 
 airborne and ground-based radar surveys have mapped: a) the lake outline\,
  b) the ice thickness in the region and c) the internal structure of the i
 ce sheet. Radar surveys reveal that SLE lies beneath 3.2 km of ice in a de
 ep\, topographically controlled fjord-like valley\, is 11.9 km long and ha
 s a maximum width of 2.9 km. Between November 2007 and February 2008 five 
 seismic reflection survey lines were collected perpendicular to the long a
 xis of the lake at 1.4 km intervals. The seismic profiles show the steep v
 alley side-walls\, lake water depths and the morphology and composition of
  the lakebed. The seismic profiles indicate that the thickness of the wate
 r-body increases down-lake from a maximum depth of 50 m on the up-flow pro
 file to a maximum depth of nearly 160 m on the down-flow profile\, produci
 ng a water volume of 1.4 km3\, suggesting that SLE is a substantial body o
 f water. The lake bed is composed of high-porosity\, low-density sediments
  with acoustic properties very similar to material found on the deep ocean
  floor. Seismic reflections indicate a substantial thickness of this soft 
 sedimentary material\, accumulated at the lake bed in a low-energy environ
 ment. Modelled basal mass balance suggests that nearly 80% of the ice wate
 r interface is at the melting point. A thin 15 m thickness of accretion ic
 e forms at the down-ice-flow end of the lake. Geophysical results confirm 
 that SLE is an ideal target for in-situ sampling and indicate significant 
 practical implications for the lake access operation. 
LOCATION:Scott Polar Research Institute\, LIBRARY (1ST FLOOR)
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