HR: 1340h
AN: G33B-1231    [Abstracts]
TI: All Quiet on the Seaward Ice Front?
AU: * MacAyeal, D R
EM: drm7@midway.uchicago.edu
AF: University of Chicago, Department of Geophysical Sciences 5734 S. Ellis Ave., Chicago, IL 60637, United States
AU: King, M A
EM: m.a.king@ncl.ac.uk
AF: Newcastle University, School of Civil Engineering and Geosciences, Cassie Bldg., Newcastle upon Tyne, NE1 7RU, United Kingdom
AU: Bassis, J N
EM: bassis@ucsd.edu
AF: University of Chicago, Department of Geophysical Sciences 5734 S. Ellis Ave., Chicago, IL 60637, United States
AU: Brunt, K M
EM: kbrunt@uchicago.edu
AF: University of Chicago, Department of Geophysical Sciences 5734 S. Ellis Ave., Chicago, IL 60637, United States
AB: Horizontal flow of Antarcticaês great ice streams is temporally variable on diurnal and semidiurnal time-scales associated with ocean tides. Sometimes the ice streams exhibit sudden movement pulsations lasting less than hours, but modulated strongly in the diurnal and sub-diurnal time frame ( e.g., Whillans Ice Stream (formerly B)). In other cases, ice-stream flow appears to vary continuously over time in concert with the tide ( e.g., Bindschadler Ice Stream (formerly D)) or with the spring-to-neap tidal cycle ( e.g., Rutford Ice Stream), and can wiggle from side to side in addition to surging forward in the direction of flow. In all cases, these ice-streams enter large floating ice shelves that, to a large degree, control their time-average discharge through the application of backpressure. The present study examines a series of continuous GPS measurements of ice- shelf flow at three stations near the seaward ice front of the Ross Ice Shelf associated with a measurement campaign lasting 23 days. The measurements reveal smooth, sinusoidal variability in the horizontal ice-shelf flow consistent with a linear response to ocean tidal fields. Given the fact that much of the ice shelfês flow speed is determined by ice-stream inflow velocity at the grounding line, and given that this velocity can be strongly pulsed (at least at the grounding line of the Whillans Ice Stream), why are there no velocity pulsations at the ice front? If temporal variability of ice-stream inflow is damped within the ice-shelf interior, temporal variations at the ice front will be –quiet" at least as far as the temporal signal introduced by ice-stream flow is considered. If temporal variability at the seaward ice front retains some of the pulsation associated with ice-stream inflow-- an unquiet seaward ice front--then ice-stream conditions have the ability to potentially alter ice-shelf flow at the sensitive iceberg-calving margin. This would constitute an important interrelationship between ice-stream and ice-shelf dynamism.
DE: 0728 Ice shelves
DE: 0730 Ice streams
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 1223 Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions (0762, 1218, 3319, 4550)
DE: 7299 General or miscellaneous
SC: Geodesy [G]
MN: 2007 Fall Meeting