HR: 16:15h
AN: C44A-02 INVITED     [Abstracts]
TI: Ice streams stop and start: evidence from the Ross Ice Shelf, interpreted using numerical models of ice shelf flow
AU: * Hulbe, C
EM: chulbe@pdx.edu
AF: Department of Geology Portland State University, PO Box 751, Portland, OR 97207-0751 United States
AU: Fahnestock, M
EM: mark.fahnestock@unh.edu
AF: Institute for the Study of Earth, Oceans, and Space University of New Hampshire, Morse Hall 39 College Road, Durham, NH 03824-3525 United States
AU: Shuman, C
EM: Christopher.A.Shuman@nasa.gov
AF: Cryospheric Sciences Branch NASA Goddard Space Flight Center, Code 614.1 Room A210 Building 33, Greenbelt, MD 20771 United States
AB: Flow features on the surface of the Ross Ice Shelf, West Antarctica, record two episodes of ice stream stopping and reactivation within the last 1000 years. Whillans Ice Stream (formerly B) must have stopped its rapid flow about 850 calendar years ago and restarted about 400 years later and MacAyeal Ice Stream (formerly E) either stopped or slowed significantly between 800 and 700 years ago, restarting about 100 years later. We document these events using maps of streaklines emerging from individual ice streams, together with numerical models of ice shelf flow. Forward model experiments demonstrate that only a limited set of discharge scenarios could have produced the current streakline configuration. In contrast, spatial variation in ice shelf thickness does not apear to be a particularly useful diagnostic for past ice stream discharge cycles. Previously, ice-stream scenarios emphasized runaway retreat or stagnation on millennial time scales. Here, we identify a new scenario: century-scale off/on cycles. This introduces uncertainty into predictions for future sea-level withdrawls by the West Antarctic Ice Sheet, which are based in part on recent slowing of Whillans Ice Stream and the "stopped" condition of Kamb Ice Stream.
DE: 0728 Ice shelves
DE: 0730 Ice streams
DE: 0774 Dynamics
DE: 0798 Modeling
DE: 8005 Folds and folding
SC: Cryosphere [C]
MN: Fall Meeting 2005