WISSARD Hot Water Drill System design and overall description

A new, clean, hot-water drill system (HWDS) was developed by the ANDRILL Science Management Office, University of Nebraska-Lincoln, for use in the Whillans Ice Stream Subglacial Access Research Drilling (WISSARD) project to gain access to Subglacial Lake Whillans (SLW) in January 2013 beneath ~800 m of ice in West Antarctica (84.240 S, 153.694 W), as well as at the grounding zone (GZ) of the Ross Ice Shelf beneath ~730 meters of ice in January 2014 at a location about 60 miles north of the SLW site. Testing of the WISSARD hot water drill system was performed on the McMurdo Ice Shelf near McMurdo Station in December 2012 at a location named WIZ-SPOT (77.890278 S, 167.008333E)

One primary borehole was drilled into the basal ice environment of SLW during the initial field season in 2012/13. A series of three related papers published in the Annals of Glaciology, v. 55 (68), describe the process of designing, fabricating, assembling, shipping, testing, commissioning and traversing the WISSARD HWDS, as well as providing details about the snow melting system that supplied seed water for the drill and the design of the control and monitoring system.

The first scientific use of the WISSARD hot water drill system provided clean access through ~800 meters of ice into Subglacial Lake Whillans (SLW) in late January 2013. This is described in a paper by Tulaczyk and other (2014) published in the Annals of Glaciology v. 55(65), which includes the deployment of an array of scientific tools through the SLW 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. Observations confirm the existence of a subglacial water reservoir whose presence was previously 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 -0.558C, consistent with depression of the freezing point by 7.019MPa of water pressure. Subglacial water was turbid and remained turbid following filtration through 0.45 mm filters. The recovered sediment cores, which sampled down to 0.8 m below the lake bottom, contained a macroscopically structureless diamicton with shear strength between 2 and 6kPa.