Study Area

Whillans/Mercer active lakes

Intro

The WISSARD project focuses on the lower portion of the Whillans Ice Stream (formerly Ice Stream B) on the Siple Coast in West Antarctica, which has long been the focus of field-work within the US Antarctic Program. In 2007, an extensive hydrological system under Whillans and Mercer ice streams was discovered through analysis of ICESat laser altimetry data. There are two main sites for the WISSARD project: i) one of the active subglacial lakes and ii) a region of the grounding zone downstream of the lake.

Subglacial Lake Whillans

Subglacial Lake Whillans (SLW) is an active subglacial lake on lower Whillans Ice Stream. The ICESat data detected deformation of the ice surface in response to subglacial water activity [Fricker et al., 2007; Fricker and Scambos, 2009], and were used to monitor the activity of SLW intermittently between October 2003 and October 2009. During this time there were two complete fill/drain cycles (see Figure). There are no data available before ICESat, so it is not known how long the lake had been quiescent before 2003. However these data do allow for a periodic drainage cycle with a residence time on the order of three years.

SLW is an ideal candidate for drilling for the following reasons:

  • It is located beneath a major West Antarctic ice stream that is known to have highly variable surface velocity
  • Safety/accessibility considerations
    • no visible surface crevassing
    • close to the grounding line (~80 km)
    • accessible from McMurdo Station
    • relatively thin ice thickness (800 m); for comparison, ice thicknesses over Subglacial Lake Ellsworth and Subglacial Lake Vostok, are ~3 km and ~4 km respectively.
  • Low contamination risk: lake sits at the seaward end of the hydrologic catchment, which alleviates concern over inadvertent biological contamination. Due to its location, any potential environmental impact would be confined to a limited area close to the ocean with a relatively short hydraulic residence time.

Grounding zone

The most likely flow-path from SLW to the grounding line has been estimated from the hydrostatic hydropotential derived from a surface DEM and bedrock DEM, and suggests that the outflow enters the Ross Ice Shelf cavity in an embayment near (84.35°S, 163.06°W) (see Figure). The final location of the grounding zone site will depend on our geophysical site surveys, which will include collecting extensive high-resolution radar and seismic data. Surveying this part of the grounding zone will allow us to determine the effect of lakes on grounding zone processes and their stability, and vice versa, in addition to their effect on subglacial sedimentary processes and ocean-induced basal melting.