HR: 0800h
AN: C41B-0477    [Abstracts]
TI: Ice Flow History, Basal Melt, and Hydraulic Connections in the Dome C Lake District Headwaters Over the Last Glacial Cycle Inferred from Hyrdopotential, Internal Layers, and Basal Reflectvity in Airborne Radar Sounding Data
AU: * Carter, S P
EM: sasha@ig.utexas.edu
AF: Univerity of Texas at Austin Institute for Geophysics, John A. and Katherine G. Jackson School of Geosicences, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road (R2200), Austin, TX 78758-4445, United States
AU: Blankenship, D D
EM: blank@ig.utexas.edu
AF: Univerity of Texas at Austin Institute for Geophysics, John A. and Katherine G. Jackson School of Geosicences, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road (R2200), Austin, TX 78758-4445, United States
AU: Young, D A
EM: duncan@ig.utexas.edu
AF: Univerity of Texas at Austin Institute for Geophysics, John A. and Katherine G. Jackson School of Geosicences, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road (R2200), Austin, TX 78758-4445, United States
AU: Holt, J W
EM: jack@ig.utexas.edu
AF: Univerity of Texas at Austin Institute for Geophysics, John A. and Katherine G. Jackson School of Geosicences, J.J. Pickle Research Campus, Bldg. 196; 10100 Burnet Road (R2200), Austin, TX 78758-4445, United States
AB: We have tracked 11 dated isochronal layers in the vicinity of Dome C using airborne ice-penetrating radar data for the purposes of calculating vertical strain and estimating horizontal velocity. Using the calculated vertical strain and a back-stripping of the layers we then obtain paleo-accumulation rates for the last 127 k. Combining the strain rate, accumulation history with a surface temperature record from the EPICA Dome C ice core, an assumed lapse rate of 10 degrees per km of elevation and a small linear correction for horizontal advection, we are able to calculate a long-term temperature model for every record of radar data. Characteristically lenticular features in the internal layer structure, associated with accumulation highs at the upstream ends of subglacial lakes Concordia and Horseshoe, are tracked to reveal horizontal velocities of 0.5 and 0.75 m/yr respectively. Velocities in both locations appear to have decreased during glacial maxima to a value nearly half that found during the interglacials. The modern velocities are consistent with those obtained from InSAR satellite measurements. Layer-based paleo-accumulation rates indicate that the present inferred distribution of accumulation rates is broadly equal to the accumulation distribution during the Eemian interglacial. Rates during the last glacial maximum were roughly ½ to 1/3 the rates found presently. Our temperature model reveals that a significant portion of the basal ice in the Dome C region may be at or near the pressure melting point, consistent with other published results from Dome C ice Core. Widely distributed melt rates in the major topographic valleys are generally less than 1 mm/yr throughout the region with slightly higher melts in the basin draining into Vincennes Subglacial Lake. The two largest subglacial lakes within the survey, Concordia and Vincennes are both associated with enhanced basal melting on their upstream shores at rates locally greater than 2 mm/year. Although published estimates for geothermal flux are capable of explaining the behavior of ice and water in most of the area, the two melt anomalies associated with the two largest subglacial lakes require an additional source of basal heat. These results have major implications for the filling rates and histories of several of the known subglacial lakes in this region.
DE: 0726 Ice sheets
DE: 0776 Glaciology (1621, 1827, 1863)
DE: 0794 Instruments and techniques
DE: 6900 RADIO SCIENCE
SC: Cryosphere [C]
MN: 2007 Fall Meeting