University of Cambridge > Talks.cam > Scott Polar Research Institute - Physical Sciences Seminar > Geophysical surveys of Subglacial Lake Ellsworth, West Antarctica: implications for in-situ exploration

Geophysical surveys of Subglacial Lake Ellsworth, West Antarctica: implications for in-situ exploration

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In addition to exerting a significant impact on ice sheet dynamics, subglacial lakes are expected to contain unique life forms and records of ice sheet history. To date, none of the ~150 Antarctic lakes discovered from radio echo sounding surveys have been accessed directly. The Ellsworth 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 ice sheet. Radar surveys reveal that SLE lies beneath 3.2 km of ice in a deep, topographically controlled fjord-like valley, is 11.9 km long and has a maximum width of 2.9 km. Between November 2007 and February 2008 five seismic reflection survey lines were collected perpendicular to the long axis of the lake at 1.4 km intervals. The seismic profiles show the steep valley side-walls, lake water depths and the morphology and composition of the lakebed. The seismic profiles indicate that the thickness of the water-body increases down-lake from a maximum depth of 50 m on the up-flow profile to a maximum depth of nearly 160 m on the down-flow profile, producing a water volume of 1.4 km3, suggesting that SLE is a substantial body of 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 environment. Modelled basal mass balance suggests that nearly 80% of the ice water interface is at the melting point. A thin 15 m thickness of accretion ice 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.

This talk is part of the Scott Polar Research Institute - Physical Sciences Seminar series.

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