HR: 0830h
AN: C11C-0841    [PDF]
TI: WIND AND SURFACE TOPOGRAPHY AS A CAUSE OF STRATIGRAPHIC DEFORMATION IN WEST ANTARCTICA
AU: Arcone, S A
EM: steven.a.arcone@erdc.usace.army.mil
AF: U.S. Army ERDC/Cold Regions Research and Engineering laboratory, 72 Lyme Road, Hanover, NH 03755 United States
AU: * Spikes, V B
EM: vandy.spikes@maine.edu
AF: Climate Change Institute, 5790 Bryand Global Sciences Center University of Maine, Orono, ME 04469 United States
AB: The stratigraphy of firn and ice in polar ice sheets is important for core site selection, and reveals information on the complex processes of flow, deformation and deposition. We are interested in how some of the deformation that we have observed with ground-based, 400-MHz ground-penetrating radar profiles evolves in the firn regime of West Antarctica. It has long been known that wind decreases deposition on downwind slopes and increases it on upwind slopes. What are not known are the degree to which this happens, and the stratigraphic consequences at depth. We discuss a 177 km profile recorded during the ITASE project that originated at Byrd Surface Camp, and whose westerly direction was within 30 degrees of alignment with the downglacier wind and also, with the direction of ice flow. The measured flow speeds of 11 m/a (at Byrd, upglacier) to 48 m/a (downglacier) indicate that the ice was in extension, so that compressive forces could not have caused the folding and pinching. We compare surface slopes with the total accumulation from 1988-1999 to show the degree to which wind diminished accumulation on the leeward slopes (facing downglacier) and increased it on the windward slopes (facing upglacier). The sensitivity of this process to slopes less than a few tenths of a degree is impressive. The strong deformation in the deeper firn stratigraphy is then seen to be apparent because it directly results from the spatial differences in accumulation rates. Some stratigraphic horizons dip as much as 16 m over a few km, and some horizons exhibit total depth changes of up to 30 m over about half the length of the profile. The spatial stability of many fold hinges with depth suggests that the upglacier migration of surface topography that results from the variable accumulation rates may be balanced by the ice flow. Other, deeper radar profiles acquired during ITASE show that the scale of the apparent folding greatly increases with depth.
DE: 0925 Magnetic and electrical methods
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 8005 Folds and folding
SC: Cryosphere [C]
MN: 2003 Fall Meeting