Geodetic and Seismic Observations of Ice-Stream Dynamics

Open Access
Author:
Winberry, Jeremy Paul
Graduate Program:
Geosciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 23, 2008
Committee Members:
  • Sridhar Anandakrishnan, Committee Chair
  • Richard B Alley, Committee Member
  • Charles James Ammon, Committee Member
  • Derrick L Lampkin, Committee Member
Keywords:
  • seismology
  • ice sheet
  • ice stream
Abstract:
The mass balance of large ice sheets is controlled by the dynamics of fast moving ice streams and outlet glaciers. In this work, I use geodetic and passive seismic observations to constrain rates of change in the flow of ice streams and illumi- nate fundamental processes that govern their behavior. An investigation of the flow field near the onset of Bindschadler Ice Streams reveals that the ice stream onset location is presently stable. Using passive seismic observations to monitor subglacial processes on MacAyeal Ice Stream, a set of harmonic glacial tremors were observed. The tremors are characterized by the sustained arrival 3 Hz energy for over 10 minutes, during which the source location migrates. The duration, monochromatic nature, and movement indicate the source mechanism is transient flow in the subglacial water system. A detailed investigation of the stick-slip mo- tion on Whillans Ice Stream is undertaken using detailed GPS observations of the surface velocity. These observations reveal that most aspects of stick-slip motion are modulated by the tides of the Ross Sea. The tides affect ice stream by introducing rates in which stress is accumulated during the time periods between slip events.