WISSARD at Subglacial Lake Whillans, West Antarctica:scientific operations and initial observations
Friday, 19 December 2014: 11:50 AM
Subglacial Lake Whillans (SLW) is a shallow subglacial water reservoir covered by 800m of ice. A custom-built hot-water drill was used to access SLW in a microbiologically clean way in late January 2013. Lake access for sampling and in-situ measurements was maintained for a total of 3 days. We deployed an array of scientific tools through a large diameter borehole: a downhole camera, a conductivity–temperature–depth (CTD) probe, a Niskin water sampler, an in situ filtration unit, three different sediment corers, a geothermal probe and a geophysical sensor string. We confirm the existence of a subglacial water body whose presence was inferred from satellite altimetry and surface geophysics. Subglacial water is about two orders of magnitude less saline than sea water (0.37–0.41 psu vs 35 psu) and two orders of magnitude more saline than pure drill meltwater (<0.002 psu). It reaches a minimum temperature of –0.55 degrees C, consistent with depression of the freezing point by pressure from ca. 800m of ice. Subglacial remained turbid throughout the observation period. The recovered sediment cores contained a macroscopically structureless diamicton with shear strength between 2 and 6 kPa. Our recommendation for future subglacial access through water-filled boreholes in cold ice is to supply heat to the top of the borehole to keep it from freezing. Development of a centimeters-thick ice layer on top of the borehole water column prevented deployment of some light borehole tools.