2002-2003 Science Planning Summary

Glaciology

Dr. Julie Palais
Program Manager

IO-209-O

NSF/OPP 00-87345
Station: McMurdo Station
RPSC POC: Curt LaBombard
Research Site(s): Byrd Surface Camp

Western Divide WAISCORES site selection
Dr. Howard B. Conway
University of Washington
Department of Geophysics
conway@geophys.washington.edu
http://www.ig.utexas.edu/research/projects/wais/inland/inland.htm

Deploying Team Members: Ginny Catania . Howard B Conway . Maurice E Conway . Felix S Ng . Erin C Pettit
Research Objectives: The West Antarctic Ice Cores (WAISCORES) community has identified the western divide, between the Ross embayment and the Amundsen Sea, as the region for the next deep-ice core. The Ice Core Working Group (ICWG) has developed a document (WAISCORES: Science and Implementation Plan, 2000) that outlines the objectives of the drilling and the physical and chemical properties the core must have to achieve those objectives.

The divide region spans more than 40,000 square kilometers, and preliminary site selection using airborne geophysical methods is now underway. This work has identified several potential drilling sites where the climate record should be best preserved throughout its long history of ice dynamics. Researchers will place a suite of ground-based geophysical measurements to map spatial variations of iceflow, accumulation rate, internal layering, and ice thickness at two of the most promising sites. The chief investigative tools include:

High and low frequency ice-penetrating radar

Repeat global positioning system surveys to calculate the present-day surface velocity field

Synthetic aperture radar interferometry to calculate the regional velocity field

Short firn cores to calculate present-day accumulation rates.

Beyond the initial mapping and interpretation of internal layers and surface velocity, the measurements will be used to constrain iceflow modeling. In particular, researchers will use these measurements and models to identify a site that is most likely to satisfy the following ICWG criteria:

Minimal disturbance from an iceflow,

A record that extends back at least 50,000 years

Countable annual layers back 20,000 years.

A fourth criterion (the good preservation of chemical species) will be addressed by other projects.

The first criterion (minimal disturbances) will be evident from the patterns of radar-detected internal layers. To address the other two, researchers will use the measurements as input for time-dependent iceflow and temperature models that predict depth variations of age, layer thickness, and temperature. The mismatch between the model predictions and the data eventually recovered from the core will help infer thinning and climate histories for the region, in addition to yielding an estimate of expected conditions before drilling. The information gathered will help guide site selection for the drilling.


Field Season Overview:
Project team members will travel to Byrd Surface Camp by fixed wing aircraft. From there they will traverse to a site selected last season and use radar and GPS to collect a suite of ground-based measurements to map detailed spatial variations of ice flow, accumulation, internal layering and ice thickness. The selected site is expected to yield a 3000 - 3500 meter long core.