HR: 15:10h
AN: C33D-07    [Abstracts]
TI: Biweekly variation in the flow speeds of Rutford Ice Stream, West Antarctica.
AU: * Gudmundsson, G H
EM: ghg@bas.ac.uk
AF: British Antarctic Survey, High Cross, Madingley Rd , Cambridge, CB3 0ET United Kingdom
AB: GPS measurements conducted in Dec 2003 to February 2004 on Rutford Ice Stream revealed fluctuations in surface velocities with a periodicity of two weeks. Tidal-analysis of the data, and comparison with GPS measurements made in the same time period on Ronnie Ice Shelf, show these temporal variations in flow to be tidally controlled and related to spring-neap tidal cycles. In total, five GPS stations were operated on the ice stream over a period of about 50 days. A further reference station was situated on Fletcher Promontory. Distance from the reference station to all other GPS units was less than 60 km. Positions were calculated using the local reference station, and by the use of precise point processing. In contrast to what similar type of measurements have reviled on the ice plain of Whillans Ice Stream, there is no indication of any stick-slip motion on the Rutford Ice Stream. Tidal effects on flow were observed at the upper-most station some 50 km upstream from the grounding line. Analysis of the spatial variation in tidal amplitudes constituents suggests that tides affect the flow some tens of km further upstream. Preliminary model calculations suggest that the lack of any diurnal variability in surface velocities may be caused by the particular bed-to-surface transfer characterisitcs of the ice stream.
DE: 1827 Glaciology (1863)
DE: 1255 Tides--ocean (4560)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting