Project Summary:

Collaborative Research: WAIS Ice Divide Migration

Collapse of the West Antarctic Ice Sheet (WAIS) has been proposed from both sides of the ice divide separating the Ross Embayment from the Amundsen Sea. A dramatic rise in sea level could be in our future if such a collapse is underway. If either or both collapse hypotheses are correct, the ice divide should be migrating now. The internal layering seen by ice-penetrating radar gives us two ways to look for evidence of past or ongoing divide migration. First, the special character of ice flow at an ice divide leaves internal layers (isochrons) at shallower depths under the divide than at the flanks, and divide migration perturbs this isochron bump in predictable ways indicative of the divide migration pattern. Second, spatial variations in accumulation rate, caused by surface slope variations, create thick and thin spots in the layers. The locus of these thick or thin spots can be mapped by radar back to the site of origin. The slopes of these tracks contain a record of the ice flow speed and direction where they were deposited at the surface. When the layers can also be dated (e.g. by an ice core such as Byrd), then absolute velocities can be determined through ice flow modelling.

We propose to look for evidence of migration of the Amundsen-Ross ice divide by collecting airborne ice penetrating radar, laser altimeter and GPS positioning data with the SOAR Twin Otter aircraft along 9 ice flow lines crossing the divide. We will use these data together with ice flow models to infer an ice divide migration history. In addition, the radar will reveal recent patterns of accumulation rate along important parts of the U.S. ITASE traverse route, where this international project plans to study climate patterns over the past 200 years. Finally, our proposed flow lines for data acquisition and modelling cross the sinuous ridge section of the ice divide, in the area targeted for the WAISCORES deep ice core that will be drilled in the near future. Our analysis of the flow at the ice divide should provide important time scale and layer thickness information for the ice core project.

This is a collaborative proposal; radar data reduction and analysis will be handled at University of Texas Institute of Geophysics (UTIG) by Don Blankenship and David Morse, and the ice flow modelling and interpretation work will be carried out collaboratively by Ed Waddington at University of Washington and David Morse at UTIG.