On siphons and sediments: A new model for draining active subglacial lakes in Antarctica informed with satellite radar and laser altimeter observations.

Abstract:

With the advent of repeat-pass satellite-based surface altimetry over much of Antarctica, approximately 130 new subglacial lakes have been discovered entirely from observations of surface uplift and subsidence; these are commonly referred to as “active lakes”. In contrast to the ~160 lakes detected by radar sounding (“RES” lakes), which are typically in mountains bedrock terrain near the ice divide and static with residence times spanning millenia, active lakes are typically located in fast flowing ice streams far from the divides, and have short residence times. To understand how water transfers through active lake systems we have developed a new model based on earlier theoretical work and informed by lake-volume estimates inferred from of ice surface displacements detected by satellite radar and laser altimetry. We find that although the overall pattern of filling and drainage is similar to that for ice dammed lakes in alpine regions via channels thermally eroded into the ice that then creeps shut as water pressure declines, Antarctic lake drainage is better simulated by invoking a channel mechanically eroded into the underlying sediment. The necessity of an erodable deformable substrate to explain lake drainage suggests that the distribution of active lakes is an indicator for the presence of sediment. Furthermore the process of lake drainage appears quite sensitive to the composion and strength of the underlying till. We explore these possibilities by testing the model on subglacial lakes in both East and West Antarctica, including Recovery Glacier and MacAyeal Ice stream.