Interpreting summertime speedup of the Greenland ice sheet in the context of borehole observations of the subglacial hydraulic system

We present preliminary results from boreholes drilled to the base of the Greenland ice sheet in the Pakitsoq region downstream from Swiss Camp. Boreholes offer a rare opportunity to make direct measurements at the bed and in the ice. In the summer of 2011 roughly one dozen holes were drilled at two separate sites downstream from Swiss Camp, Greenland. At each site we deployed thermistors, water pressure sensors, sliding meters, strain gauges, conductivity probes and inclinometers. In addition, pressure sensors were installed in in nearby moulins and a down-hole camera logged englacial structures in boreholes. Slug tests were performed to test the capacity and efficiency of the subglacial system. Our downstream site was also the location where an extensive borehole and surface seismometer array were deployed. These data are interpreted in the context of surface melt availability (derived from locally installed weather stations and a characterization of the supraglacial stream and lake networks) and surface velocity changes (derived from an along-flow array of GPS receivers).