Ph.D., Geophysics, California Institute of Technology, 1969
Areas of Interest:
Glaciology, glacier, and ice sheet dynamics
My interest in glaciers was kindled by the beauty that they add to the mountain landscape. As a scientist, I am intrigued by how glaciers and ice sheets move, how they interact with the terrain on which they lie and how they are related to the climate of the earth.
Most fluctuations of glaciers and ice sheets (land ice) are forced by changes in climate. In principal, it is possible to invert the history of land-ice fluctuations as deduced from historical or geological information to infer some aspects of the past climate. Solution of that inverse problem can expand paleoclimate information to remote mountain locations and time intervals where there are no direct measurements from weather instruments.
Similarly, it is of interest to predict what changes can happen to present land ice under projections of climate in the future. This question is significant with regard to how run off from glaciated mountain regions may be altered in the future. The potential large effect of ice sheets on global sea level is especially important.
My research takes a combined observational/theoretical approach to understanding processes that influence these connections to the past and the future. I also attempt to develop models based on these processes that illuminate the appropriate level of model complexity that is required depending on the desired spatial and temporal resolution.
Some glaciers experience rapid changes caused by surges in their down-slope motion that are unrelated to climate. Similar behavior is suspected to be possible in large ice sheets, especially ones that are grounded below sea level. The most important modern example is the West Antarctic Ice Sheet, where the discharge of ice to the ocean occurs through bands of rapidly moving ice called ice streams. These phenomena complicate the connection between land ice and climate, and indicate that internal instabilities in the flow mechanics can affect local environment and in the case of ice sheets impact global sea level. One of my long term interests has been the mechanism of fast flow acting in surging glaciers and ice streams and how the fast flow may be switched on and off.
The principal observations in my recent research involve the measurement of ice motion and geometry using Global Positioning System (GPS) and traditional geodetic survey methods coupled to radar-echo sounding through the ice thickness to the bed. A recent focus has been interpretation of the geometry of stratigraphic layers detected by radar in the Antarctic Ice Sheet to infer features of its flow history. The flow history is important for interpretation of ice cores to get high resolution records of paleoclimate. It also reveals information about the long term changes in ice streams draining the West Antarctic Ice Sheet and the potential future effect of this ice sheet on sea level.