The flow history of Siple Dome and Ice Streams C and D, West Antarctica: Inferences from geophysical measurements and ice flow models.

摘要

Siple Dome {dollar}(81.65spcirc{dollar} S. {dollar}148.81spcirc{dollar} W) is an ice ridge between Ice Streams C and D on the Siple Coast of West Antarctica. Its location near the coast and between two ice streams makes it a favorable place for the study of paleo-climate and paleo-ice-stream activity. The analyses presented in this dissertation are based on geophysical measurements made at Siple Dome in 1994 and 1996 as part of a collaborative project among the University of Washington, St. Olaf College, and the University of Colorado. The measurements were made to characterize the geometry of the dome, investigate its stability, infer possible changes in the ice stream configuration, and support an ice core paleo-climate project at the Siple Dome summit.; In this dissertation, geophysical measurements are used with quasi-time-dependent ice flow models and inverse methods to infer the history of ice flow at Siple Dome and place limits on the past activity of adjacent ice streams C and D. Information about past ice flow is inferred primarily from the shapes of internal layers detected across Siple Dome from radio-echo sounding measurements. The continuity of the internal layers and the shape of a warp feature in the layer pattern at the divide suggest that Siple dome has not been over-run by ice streams over the past {dollar}10sp4{dollar} years and that the divide position has been slowly migrating northward toward Ice Stream D for the past few thousand years. Gradual thinning of the boundary between Siple Dome and a relict piece of Ice Stream C prior to its stagnation may be responsible for the divide migration. The pattern of ice thickness change across the south flank of Siple Dome, calculated from measurements of ice flow and an inferred accumulation pattern, is interpreted as a response to recent {dollar}({lcub}<{rcub}500{dollar} a) stagnation of a piece of Ice Stream C adjacent to Siple Dome. The topography of surface lineations on the Ice Stream D-side of Siple Dome indicates recent {dollar}({lcub}<{rcub}{dollar}500 a) stagnation of another relict ice stream. These recent stagnation events may represent a major reorganization of the ice stream system around Siple Dome after a relatively stable period which lasted several thousand years.