HR: 0800h
AN: C51A-0262    [Abstracts]
TI: Radar Studies of the Trunk and `Sticky Spot' of Kamb Ice Stream
AU: * Jacobel, R W
EM: jacobel@stolaf.edu
AF: Physics Department St. Olaf College, 1520 St. Olaf Ave., Northfield, MN 55057 United States
AU: Pettersson, R
EM: petterss@stolaf.edu
AF: Physics Department St. Olaf College, 1520 St. Olaf Ave., Northfield, MN 55057 United States
AU: Osterhouse, D
EM: osterhou@stolaf.edu
AF: Physics Department St. Olaf College, 1520 St. Olaf Ave., Northfield, MN 55057 United States
AU: Tulaczyk, S
EM: tulaczyk@es.ucsc.edu
AF: Department of Earth Sciences University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 United States
AU: Howat, I
EM: ihowat@es.ucsc.edu
AF: Department of Earth Sciences University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 United States
AB: During the 2004-05 Antarctic field season we acquired approximately 275 km of ground-based ice-penetrating radar data on the trunk of Kamb Ice Stream (KIS) as a part of a two-year program of radar and GPS studies examining the possibility of ice stream reactivation. Many of the profiles explore a region of near-stagnant ice, the `sticky spot', in the vicinity of camps occupied by a number of groups from 1986-2000 and which was the focus of extensive borehole studies by Cal Tech in 1996 and 2000. We also investigated an area of the trunk approximately 80 km upstream where repeat laser altimeter profiling revealed an anomalous 4m surface uplift of between 1998-2000 (Spikes, et al., 2003). The radar data image bedrock and internal layer stratigraphy in detail; in many cases the layers are present nearly to the bottom. We have identified a bright layer at about two-thirds to three-fourths of the ice thickness in all profiles. This is likely is the same bright layer that we have detected throughout West Antarctica in ITASE traverses and dated to 17.5 KY (Jacobel and Welch, 2004). We have also produced maps of variations in bed reflectivity that correspond closely (but not identically) with the surface expression of the sticky spot in satellite imagery. Bright areas of the bed are found in the trunk of the ice stream on both sides of the sticky spot and also along the south margin where a layer of liquid water was identified in Cal Tech bore hole 00-01 (Englehart et al., in press). However, the brightest bed reflections are found in the area of anomalous surface uplift. Echoes from near the bed at this location indicate the possible presence of a highly reflective surface off to one side of our profiles. Our bed amplitude studies are augmented by two densely-spaced constant midpoint profiles that enable us to characterize attenuation and e/m wave speed within the ice at locations that are both stagnant and fast-moving. In addition, we have re-imaged fold features in the internal layering of the ice that correspond to structures seen in our 1988 ground-based radar studies at UpC when the sticky spot was first identified as overlying an area of raised bedrock (Jacobel et al., 1993, Retzlaff et al., 1993). These two surveys enable us to measure components of the accumulated strain over the intervening 16 years.
DE: 0730 Ice streams
DE: 0758 Remote sensing
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005