HR: 11:35h
AN: C42A-06    [Abstracts]
TI: Century-Scale Ice Stream Variability and Stability: A case study of Kamb Ice Stream, West Antarctica.
AU: * Catania, G A
EM: gcatania@ig.utexas.edu
AF: Institute for Geophysics, 4412 Spicewood Springs Rd. Unit 600 University of Texas, Austin, TX 78759 United States
AU: Scambos, T
EM: teds@icehouse.colorado.edu
AF: National Snow and Ice Data Center, CIRES, University of Colorado, Boulder, CO 80309 United States
AU: Conway, H
EM: conway@ess.washington.edu
AF: Dept. of Earth and Space Sciences, University of Washington Box 351310, Seattle, WA 95195 United States
AU: Raymond, C
EM: charlie@ess.washington.edu
AF: Dept. of Earth and Space Sciences, University of Washington Box 351310, Seattle, WA 95195 United States
AB: Observational and model studies are synthesized to obtain a 700 year ice flow history for the Kamb Ice Stream (KIS) region of West Antarctica which is used to infer the nature and pattern of the KIS shutdown. This ice flow history reveals a dominance of short-term (order of 100 years) variability in ice stream position and discharge that is linked to changes in subglacial conditions and ice thickness. Evidence suggests that the trunk of KIS was wide, thin and temporarily ungrounded between ~550-350 years ago [Catania et al., Journal of Glaciol., in press]. Since grounded conditions currently exist throughout the trunk region we suggest that rapid changes in basal conditions were possible during the last few hundred years prior to shutdown. Simultaneous with re-grounding in the trunk region was a narrowing of the ice stream width. Such large events in the history of the ice stream may be linked to the sudden loss of fully lubricated basal conditions during the transition from ungrounded to grounded conditions and may have initiated the eventual shutdown in the ice stream trunk some 200 years later. We also observe that the short-term variability of KIS appears to be in part, controlled by neighboring Whillans Ice Stream (WIS). Examples of this include; 1) grounding throughout the trunk likely occurring because of a prior diversion in flow direction of WIS to the north, 2) migration of the northern WIS margin that was coincident with the KIS shutdown and 3) a switch in flow direction of a tributary into KIS (now flowing into WIS) [Conway et al., Nature, 419 (6906), 465-467, 2002]. Such interdependence suggests that conclusions regarding the behavior of an individual ice stream cannot be examined in isolation. In the context of long-term (1000 years) ice stream history, the observed short-term variability of one particular ice stream may be seen as "noise" within a system that is in constant flux but one that may maintain a stable mass balance over large temporal and spatial scales.
DE: 0730 Ice streams
DE: 0762 Mass balance (1218, 1223)
DE: 0774 Dynamics
DE: 0776 Glaciology (1621, 1827, 1863)
SC: Cryosphere [C]
MN: Fall Meeting 2005