Location for direct access to subglacial Lake Ellsworth: An assessment of geophysical data and modeling

Subglacial Lake Ellsworth has been proposed as a candidate for direct measurement and sampling, to identify microbial life and extract sedimentary climate records. We present a detailed characterization of the physiography of this subglacial lake from geophysical surveys, allowing bathymetry and geomorphic setting to be established. Lake Ellsworth is 14.7 km x 3.1 km with an area of 28.9 km(2). Lake depth increases downlake from 52 m to 156 m, with a water body volume of 1.37 km(3). The ice thickness suggests an unusual thermodynamic characteristic, with the critical pressure boundary intersecting the lake. Numerical modeling of water circulation has allowed accretion of basal ice to be estimated. We collate this physiographic and modeling information to confirm that Lake Ellsworth is ideal for direct access and propose an optimal drill site. The likelihood of dissolved gas exchange between the lake and the borehole is also assessed.