Speaker: Laura Stevens - Postdoctoral Fellow, Lamont-Doherty Earth Observatory
This talk will examine the influence of meltwater on two regimes of Greenland Ice Sheet flow: (1) rapid supraglacial lake drainages in the slowly-flowing inland margin, and (2) diurnal meltwater influences on fast-flowing marine-terminating outlet glaciers. In the slow-flowing regime, rapid supraglacial lake drainages provide an ideal natural experiment that enables us to probe the upper limits of meltwater’s influence on ice-flow acceleration. These lake drainages are spectacular events, where hydro-fractures drain lakes from the surface to the bed of the ice sheet in a matter of hours. This half of the talk will investigate what triggers rapid lake drainage using a Network Inversion Filter to invert a dense, local network of GPS observations during three lake drainage events. In the fast-flowing regime, marine-terminating outlet glaciers are the gatekeepers of the inland ice sheet’s access to the sea. The dynamics of these glaciers are governed by complex interactions between the atmosphere, ocean, and ice-sheet bed. This half of the talk will investigate how atmospheric and oceanic forcing influence short-term (hourly) variations in horizontal flow of Helheim Glacier, East Greenland, as observed by an array of GPS receivers. Improved mechanistic understanding of how tidal and atmospheric forcing drive marine outlet glacier flow is critical for determining how rapidly ice will be discharged into the ocean as these regions warm.