Joint geophysical observations of ice stream dynamics

Ice streams play a major role in the ice mass balance and in the reckoning of the global sea level; they have therefore been object of wide scientific interest in the last three decades. During the 21st Italian Antarctic Expedition, in the austral summer 2005-06, we deployed a joint seismographic and geodetic network in the area of the David Glacier, Southern Victoria Land. This campaign followed a similar experiment carried out in the same area during the austral summer 2003-04 with the deployment of a seismographic network that recorded significant microseismicity beneath the David Glacier, primarily occurring as a few small clusters. In the latest 2005-06 deployment, 7 seismographic stations and 3 GPS geodetic receivers operated continuously for a period of 3 months (November 2005-early February 2006) in an area of about 100x150 km2 around the David Glacier. We have carried out several analyses using the combined data sets. These included the examination of the temporal evolution in earthquake magnitude and location and also the contemporaneous observation of both seismic activity and surface kinematics of the ice stream to possibly correlate the recorded microseismicity with the movement of the glacier, affected by the Ross Sea tides. Unfortunately, a clear correlation between the occurrence of seismic events and the movement of the glacier is not evident. Here we present some details of the two temporary networks and preliminary results and implications