ACTIVE SUBGLACIAL LAKES AND THEIR INFLUENCE ON ICE STREAM DYNAMICS?

Antarctic active subglacial lakes have been first reported in 2005 (Gray et al., 2005) and within several years the number of documented active increased to over 120 (Smith et al., 2009). It appears that a significant fraction of all the subglacial water generated beneath the Antarctic ice sheet is routed through active subglacial lakes. Given the well-established general dependence of ice flow rates on subglacial water dynamics, it is important to investigate if the time-variable water flow through active subglacial lakes results in ice velocity fluctuations. Here, we will report the results of a GPS and passive seismic study focused on the response of Whillans Ice Stream, West Antarctica, to variability in active subglacial lakes. During the three years covered by this work one medium-sized active subglacial lake experienced a full cycle of filling and drainage while another one continued to fill. We use our field observations to discuss the rates at which the strength of ice-bed coupling varies through spatially and temporally. Studies of modern subglacial conditions serves to inform numerical ice sheet models that can be used to predict future sea level changes and to reproduce past ice sheet behavior.