HR: 10:35h
AN: C21D-02 INVITED     [PDF]
TI: Interactions Between Large Bedrock Features and Ice Sheet Dynamics Interpreted From Deep-Penetrating Radar Along the US-ITASE Traverse Routes
AU: * Welch, B C
EM: welchb@stolaf.edu
AF: Physics Department St. Olaf College, 1500 St. Olaf Ave., Northfield, MN 55057 United States
AU: Jacobel, R W
EM: jacobel@stolaf.edu
AF: Physics Department St. Olaf College, 1500 St. Olaf Ave., Northfield, MN 55057 United States
AU: Christianson, K
AF: Physics Department St. Olaf College, 1500 St. Olaf Ave., Northfield, MN 55057 United States
AU: Cofell-Dwyer, K
AF: Physics Department St. Olaf College, 1500 St. Olaf Ave., Northfield, MN 55057 United States
AB: Ice-penetrating radar studies depicting the structure of internal stratigraphy in ice sheets can be used to infer information about past ice dynamics and changes in ice flow over time. To date, most radar studies in the interior of major ice sheets have shown internal layers draped smoothly over bed topography with decreasing relief toward the surface. This result is one consequence of ice frozen to the bed and accumulation patterns that do not vary substantially in space or time. In contrast, areas that show significant deformation of internal layers are typically found in ice streams, where sliding can cause large strains. Deep-penetrating radar profiles from the 2001 and 2002 US-ITASE traverses show several areas in the interior of West Antarctica and the transition region between the East and West Antarctic Ice Sheets where internal stratigraphy is disrupted and discontinuous in the vicinity of large topographic bed features with relief $>$50% of regional ice thickness. Ice in these areas is presumably frozen to the bed. In some locations these disruptions in internal layers appear to result from surface wind scouring and redeposition. The influence of bed features on surface topography evidently causes local changes in snow accumulation and the interactions between wind and snow surface may facilitate the development of wind ablation regions. In another area near Byrd Surface Camp a significant bed feature, "Mt. Resnik," appears to be causing breaks in internal stratigraphy imaged in a grid of 4 radar profiles oriented across the flow direction and several kilometers downstream. We hypothesize that there is a ratio of mountain height to regional ice thickness where the ice above the mountain will effectively decouple from the surrounding ice flow and crevasses will develop. Such a scenario would cause a seam to form and disruption of internal layers that is similar to what we have observed. The fact that deeper layers in the same region are continuous implies that conditions producing the disruption may be transient, perhaps due to lowering of the ice surface. Modeling of the ice flow around this feature may provide estimates of the post-LGM thinning rates in central West Antarctica.
UR: http://www.stolaf.edu/other/cegsic/itase
DE: 1827 Glaciology (1863)
DE: 1863 Snow and ice (1827)
DE: 9310 Antarctica
SC: Cryosphere [C]
MN: 2003 Fall Meeting