[Personnel: Last_Name='BAUER', First_Name='ROB']
Discharge Variability of Ross Ice Streams Over the Last Millennium, Deduced by Numerical Simulation of Flow Features in the Ross Ice ShelfEntry ID: RossIceStreamDischarge_1ka_record
Abstract: The work, funded by NSF grant number 0296099 is in collaboration with co-PI
Mark Fahnestock. We have used composite MODIS (on NASA's Terra satellite)
imagery of flow features in the Ross Ice Shelf to infer patterns and processes
of grounding line migration over time. This involves image processing (MF),
interpretation of visual features (MF & CLH), and numerical ... simulation of both
flow-feature development and of thermodynamics along particle paths leading to
the grounding line (CLH).
The flow features reveal an episodic but continuous cycle of redirection of
ice-stream discharge and associated grounding line retreat over the last 1000
years (the time period recorded in the features). We use a simple time-domain
model of thermal evolution downstream within an ice stream to demonstrate that
fast-flowing, and thus fast-thinning, ice streams must consume basal water
supply as the ice nears the grounding line. When the meltwater (heat) supply is
exhausted, basal friction increases and flow from upstream must divert around
the now slow-flowing area. Sites of flow redirection need not be large (Crary,
Steershead, and a new ice rise forming near the downstream end of Ice Stream
ZA). The observational record shows clearly that redirection occurs, is cyclic,
and is most effective on the broad expanse of an ice plain. Such platforms for
redirection now exist downstream of the currently fast-flowing ice streams (A
and Whillans, and D and E) and probably existed downstream of Ice Stream C when
it was active. Consequences of this model are: that the rate of grounding line
retreat is modulated by internal ice sheet thermal processes, making the chance
for runaway retreat unlikely; and that the Ross ice rises do not represent
grounding events but instead formed as a result of ungrounding of surrounding
(Click for Interactive Map)
Data Set Citation
Dataset Originator/Creator: Hulbe, C.L. and M.A. Fahnestock
Dataset Title: West Antarctic ice stream discharge variability: mechanism, controls, and pattern of grounding line retreat
Role: TECHNICAL CONTACT
Email: scharfen at kryos.colorado.edu
National Snow & Ice Data Center (NSIDC) CIRES, Campus Box 449 University of Colorado
Province or State: CO
Postal Code: 80309
Hulbe, C.L. and M.A. Fahnestock, West Antarctic ice stream discharge
variability: mechanism, controls, and pattern of grounding line retreat, J.
Hulbe, C.L., W. Wang, I. R. Joughin and M. J. Siegert, The role of lateral and
vertical shear in tributary flow toward a West Antarctic ice stream, Ann.
Glaciol., 36, 244-250.
Wang, W., H. J. Zwally, C. L. Hulbe, M. J. Siegert and I.R. Joughin,
Anisotropic ice flow leading to the onset of Ice Stream D, West Antarctica:
numerical modelling based on the observations from Byrd Station borehole, Ann.
Glaciol., 37, 397-404.
Creation and Review Dates
DIF Creation Date: 2005-03-21
Last DIF Revision Date: 2009-01-08