HR: 1340h
AN: G33B-1234    [Abstracts]
TI: Mechanisms for Tidally Induced Glacier Deformation and Flow Variations, East Greenland
AU: * Davis, J L
EM: jdavis@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 42, Cambridge, MA 02138, United States
AU: Elosegui, P
EM: pelosegui@ice.csic.es
AF: Institute for Space Sciences, CSIC-IEEC Nexus, Gran Capita 2, Barcelona, 08034, Spain
AU: Hamilton, G
EM: gordon.hamilton@maine.edu
AF: University of Maine, Climate Change Institute, Orono, ME 04469, United States
AU: Stearns, L
EM: leigh.stearns@maine.edu
AF: University of Maine, Climate Change Institute, Orono, ME 04469, United States
AU: Langer, M
EM: mola@geus.dk
AF: Geological Survey of Denmark and Greenland, Geophysics Departmentt Oster Voldgade 10, Copenhagen, DK-1350, Denmark
AU: Nettles, M K
EM: nettles@ldeo.columbia.edu
AF: Columbia University Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964, United States
AU: Larsen, T B
EM: tbl@geus.dk
AF: Geological Survey of Denmark and Greenland, Geophysics Departmentt Oster Voldgade 10, Copenhagen, DK-1350, Denmark
AB: Analysis of geodetic observations from Kangerdlugssuaq and Helheim glaciers indicates that the glacier snouts are in nearly free-floating and nearly fully-grounded conditions, respectively. GPS sites on the glacier surfaces exhibit a semidiurnal vertical motion that is in phase with the ocean tides. For Kangerdlugssuaq Glacier, vertical motion and tides are of nearly equal amplitude, while for Helheim Glacier vertical motion is ~25% of the tidal amplitude. The along-flow horizontal motion of these fast moving glaciers (v > 10~meters per day at the terminus) is also modulated by the ocean tides. For data from Kangerdlugssuaq Glacier in 2005, for example, a vertical semidiurnal tidal motion of ~2~m peak-to-peak leads to along-flow position deviations (relative to mean glacier flow of ~38~m~d^-1) of ~0.5~m peak-to-peak, and flow speed variations of 10% peak-to-peak. The sense of the horizontal tidal response is such that the instantaneous flow velocity is at a minimum at ocean high tide. We consider four mechanisms for this tidal response: pressure drag, basal drag, gravitational forcing, and flexural deformation. Through consideration of these mechanisms, we use the geodetic data to place constraints on various physical parameters for the glacier. A preliminary analysis indicates that for Kangerdlugssuaq Glacier, only gravitational forcing and flexural deformation are significant contributions. We will present the geodetic data, describe the various mechanisms, and discuss the implications of our analysis.
DE: 0720 Glaciers
DE: 0770 Properties
DE: 0774 Dynamics
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: 2007 Fall Meeting