HR: 0800h
AN: C51A-0071    [Abstracts]
TI: Moho topography of the West Antarctic Rift System from inversion of aerogravity data: ramifications for geothermal heat flux and ice streaming
AU: * Studinger, M
EM: mstuding@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, United States
AB: The West Antarctic rift system, a region of thinned continental crust, dominates the lithospheric structure of the Ross Embayment in West Antarctica. Parts of the rift are host to the West Antarctic Ice Sheet, a marine-based ice sheet prone to instability. It has long been hypothesized that the lithospheric structure beneath the West Antarctic Ice Sheet is a major influence on the formation, nature and dynamics of the ice sheet. The structure of the crust- mantle boundary is a fundamental geophysical parameter for understanding lithospheric processes and for geodynamic interpretation. I use aerogravity data to derive a map of the crust/mantle boundary beneath the West Antarctic Ice Sheet and to reveal the impact of relative changes in thickness of the crust and lithosphere on surface heat flow and ice streaming. Before inverting the observed Bouguer gravity field for Moho topography the gravity effect of the crust/mantle boundary has to be isolated from shallower sources. The observed radial power spectrum is matched with the model spectra of a number of equivalent source layers. First, the short wavelengths of the observed spectrum are matched with a shallow source equivalent layer model spectrum. The model spectrum is then removed from the observed power spectrum and the remaining residual spectrum is used to match the next deeper equivalent source layer. The Moho topography derived from filtered gravity coincides well with two independent seismically determined Moho estimates. In general, the geologic contributions to continental surface heat flow can be separated into mantle heat flow and radiogenic heat flow from heat producing elements within the crust. Assuming an exponentially decreasing distribution of radioactive elements, the continental surface heat flow can be expressed as a function of crustal and lithospheric thicknesses. Within the survey area there is a region of thinner crust that corresponds to elevated heat flow of several tens of mW/m2 compared to the background level. This region coincides with the confluence and onset of several ice stream tributaries, namely Kamb Ice Stream. The region with elevated heat flow appears to pin point the location of ice stream onsets and tributaries.
UR: http://pubs.usgs.gov/of/2007/1047/ea/of2007-1047ea031.pdf
DE: 0726 Ice sheets
DE: 3010 Gravity and isostasy (1218, 1222)
DE: 3255 Spectral analysis (3205, 3280)
DE: 8109 Continental tectonics: extensional (0905)
DE: 9310 Antarctica (4207)
SC: Cryosphere [C]
MN: 2007 Fall Meeting