HR: 13:40h
AN: C43A-01 INVITED     [Abstracts]
TI: Melt Rate and Melt-Water Flow Beneath Nioghalvfjerdsfjorden Glacier, Northeast Greenland
AU: * Reeh, N
EM: nr@oersted.dtu.dk
AF: Niels Reeh, Andreas Ahlstrøm, Erik Lintz Christensen , Ørsted-DTU, Technical University of Denmark, Ørsteds plads Building 348, Kgs. Lyngby, 2800 Denmark
AU: Solgaard, A M
EM: solgaard@fys.ku.dk
AF: Anne Munck Solgaard, Gry Andrup-Henriksen, Glaciology Group, The Niels Bohr Institute, The Rockefeller Complex, Juliane Maries Vej 30, Copenhagen Ø, 2100 Denmark
AU: Andrup-Henriksen, G
EM: gry@fys.ku.dk
AF: Anne Munck Solgaard, Gry Andrup-Henriksen, Glaciology Group, The Niels Bohr Institute, The Rockefeller Complex, Juliane Maries Vej 30, Copenhagen Ø, 2100 Denmark
AU: Rignot, E
EM: eric@jpl.nasa.gov
AF: Eric Rignot, Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 United States
AU: Christensen, E L
EM: elc@oersted.dtu.dk
AF: Niels Reeh, Andreas Ahlstrøm, Erik Lintz Christensen , Ørsted-DTU, Technical University of Denmark, Ørsteds plads Building 348, Kgs. Lyngby, 2800 Denmark
AU: Forsberg, R
EM: rf@spacecenter.dk
AF: Rene Forsberg, Geodynamics Department, Danish National Space Center, Juliane Maries Vej 30, Copenhagen Ø, 2100 Denmark
AU: Ahlstrom, A
EM: aa@oersted.dtu.dk
AF: Niels Reeh, Andreas Ahlstrøm, Erik Lintz Christensen , Ørsted-DTU, Technical University of Denmark, Ørsteds plads Building 348, Kgs. Lyngby, 2800 Denmark
AB: Nioghalvfjerdsfjorden glacier, (79^o30'N, 22^oW) is an 80 km long and 20 km wide outlet glacier from the North-East Greenland ice sheet. The outermost 60 km of the glacier is afloat. A field programme was carried out on the glacier in the summer seasons of 1996, 1997, and 1998. The studies comprised observations of surface climate and mass balance, bottom melting, surface elevation, ice thickness, glacier velocity, tidal movement, and bathymetry and CTD-measurements in the sea in front of and beneath the glacier. In July 1998 detailed mapping of surface elevation and ice thickness was undertaken by means of an airborne ice-radar and laser-altimeter survey from a small aircraft. About 3000 km of high quality surface and ice thickness profiles were flown on Nioghalvfjerdsfjorden glacier. On the relatively uniform floating part of the glacier the flight tracks were 5 kilometres apart. The distance was reduced to 2.5 km near to and inside the grounding zone of the glacier. The surface velocity field was derived from repeated aerial photography in 1963 and 1978, and by Synthetic Aperture Radar Interferometry (InSAR) measurement in 1996-97 by using ERS1/2 images, and in 2004 by using Radarsat images. The measurements show a general increase of the flow velocity over the 30-year observation period. The detailed surface and ice thickness data reveal a rough relief of the glacier bottom in the grounding zone with depth amplitudes of several hundred metres over distances of a few kilometres. The thin/thick ice sections of the grounding zone continue for several kilometres in the down-glacier direction as troughs cut up into the glacier bottom, respectively as ridges extending downwards from the average bottom. However, the relief is gradually smoothed and eventually vanishes some tens of kilometres down-glacier from the grounding zone. This suggests that the melt-water flow beneath the glacier starts as channelled flow in the grounding zone but gradually turns into sheet flow with increasing distance from the grounding zone. The surface mass balance, ice thickness and velocity data are used to derive the distribution of melt-rates at the glacier bottom, on the assumption that the glacier is close to a steady state. The calculations indicate an iceflux across the grounding line of 12±1 km³/y. The calculated average bottom melt rate is 11 m/y but exceeds 30 m/y near the grounding zone.
DE: 0720 Glaciers
DE: 0758 Remote sensing
DE: 0762 Mass balance (1218, 1223)
DE: 0798 Modeling
SC: Cryosphere [C]
MN: Fall Meeting 2005