2002-2003 Science Planning Summary

Geology & Geophysics

Dr. Scott Borg
Program Manager

GO-087-M

NSF/OPP 00-03619
Station: McMurdo Station
RPSC POC: Joni English
Research Site(s): West Antarctica

A GPS network to determine crustal motions in the bedrock of the West Antarctic Ice Sheet: Phase I, Installation
Dr. Ian W. Dalziel
University of Texas Austin
Institute for Geophysics
ian@ig.utexas.edu
http://www.ig.utexas.edu/WAGN/

Deploying Team Members: Michael G Bevis . Ian W Dalziel . Eric C Kendrick . John R Roberts . Robert E Smalley, Jr
Research Objectives: The bedrock that underlies the West Antarctic Ice Sheet (WAIS) is not well described. Without a reliable evaluation of its history -- both tectonic and ice-induced crustal motions -- scientists will never fully comprehend the past, present and future dynamics of the WAIS. They cannot develop reliable global change scenarios for the future, nor accurately factor the antarctic region into global plate movements. Currently, permanent Global Positioning System (GPS) networks to measure bedrock movement are established only on the fringe of the WAIS. They cannot provide the data on subglacial volcanism, active tectonics, and ice streaming that are needed.

This project's goals re to establish baseline, long-term, reliable geodetic measurements of the crustal motion in the bedrock beneath the WAIS. The group is building a West Antarctica GPS Network (WAGN) of at least 15 GPS sites across the west antarctic interior (an area comparable to that from the Rocky Mountains to the Pacific coast) over two years beginning in the 2001-2002 austral summer.

This first summer, project team members installed the network and tested precision and velocities at the most critical sites. The network will begin to fill a major gap in GPS coverage by looking for potential bedrock movements. If crustal motions are relatively slow, meaningful results will only begin to emerge over the next 5 years or so. Once it is permanently established, however, the network should yield increasingly meaningful results with the passage of time. Indeed, the slower the rates turn out to be, the more important it is to start measuring early.

WAIS bedrock is so scattered and remote that to erect a continuous string of permanent GPS stations would rival the building of the American transcontinental railroad. Instead, the plan is to follow the Multi-modal Occupation Strategy (MOST). This entails "roving" receivers (based in permanent monuments set in solid rock outcrops) in place for only a short time at each site, providing data that can be ranged against permanent GPS readings elsewhere. Each of these "bases" can be converted in the future to a permanent, autonomous station when more logistics and satellite data linkage throughout West Antarctica are in place. When detectable motions occur, researchers can reoccupy the most critical sites, obtain more reliable velocities, and make decisions about reoccupying the entire network.

The results of this project are expected to establish important early indicators of crustal plate dynamics beneath the WAIS. As scientists take these into account in refining their models, future measurements and a time-series of the geodetic data should gradually produce a more constrained picture of WAIS subglacial dynamics. That is, plate rotations and both elastic and viscoelastic motions caused by deglaciation and ice-mass changes.


Field Season Overview:
Project team members will travel by LC-130 aircraft to a base camp at Patriot Hills. From there, a Twin Otter aircraft will provide close support to a series of remote sites where researchers will establish temporary camps and deploy precision GPS receivers. One site is a reference station that operates continuously while the other receivers are deployed. Researchers will return to the temporary camps two to seven days later to retrieve the data and equipment. From there, they will be transported via LC-130 to Byrd Surface camp, and then to Siple Dome camp where Twin Otters will provide support to new GPS sites.