C43B-0805
High-resolution, terrestrial radar velocity observations and model results reveal a strong bed at stable, tidewater Rink Isbræ, West Greenland
Thursday, 17 December 2015
Poster Hall (Moscone South)
Timothy C Bartholomaus1, Ryan T Walker2, Leigh A Stearns3, Mark A Fahnestock4, Ryan Cassotto5, Ginny A Catania6, Denis Felikson6, Mason Fried1, Dave Sutherland7, Jonathan D Nash8 and Emily Shroyer8, (1)University of Texas, Institute for Geophysics, Austin, TX, United States, (2)University of Maryland, Greenbelt, MD, United States, (3)University of Kansas, Department of Geology, Lawrence, KS, United States, (4)University of Alaska Fairbanks, Fairbanks, AK, United States, (5)University of New Hampshire Main Campus, Department of Earth Sciences, Durham, NH, United States, (6)University of Texas at Austin, Austin, TX, United States, (7)University of Oregon, Eugene, OR, United States, (8)Oregon State Univ, Corvallis, OR, United States
Abstract:
At tidewater Rink Isbræ, on the central west coast of Greenland, satellite observations reveal that glacier velocities and terminus positions have remained stable, while the lowest 25 km have thinned 30 m since 1985. Over this same time period, other tidewater glaciers in central west Greenland have retreated, thinned and accelerated. Here we present field observations and model results to show that the flow of Rink Isbræ is resisted by unusually high basal shear stresses. Terrestrial radar interferometry (TRI) observations over 9 days in summer 2014 demonstrate weak velocity response to 4 km wide, full thickness calving events. Velocities at the terminus change by +/- 10% in response to rising and falling tides within a partial-width, 2.5-km-long floating ice tongue; however these tidal perturbations damp out within 2 km of the grounding line. Inversions for basal shear stress and force balance analyses together show that basal shear stresses in excess of 300 kPa support the majority of the driving stress at thick, steep Rink Isbræ. These observational and modeling results tell a consistent story in which a strong bed may limit the unstable tidewater glacier retreats observed elsewhere. Rink Isbræ has an erosion resistant quartzite bed with low fracture density. We hypothesize that this geology may play a major role in the bed strength.
