2002-2003 Science Planning Summary

Geology & Geophysics

Dr. Scott Borg
Program Manager

GO-154-O

NSF/OPP 00-94078
Station: McMurdo and RV/IB NBP
RPSC POC: Jim Holik
Research Site(s): RV/IB NBP, McMurdo Station

CAREER: Relative frequency and phase of extreme expansions of the Antarctic ice sheets during the late Neogene
Dr. Philip J. Bart
Louisiana State University Baton Rouge
Department of Geology and Geophysics
pbart@geol.lsu.edu

Deploying Team Members: Philip J Bart . Juan M Chow . David Egan . Juan Lorenzo
Research Objectives: Expansions and contractions of the antarctic ice sheets (AISs) have undoubtedly had a profound influence on Earth's climate and global sea level. However, the cryosphere in Antarctica is not a single homogenous entity. Science has yet to embrace its three primary components -- the East Antarctic Ice Sheet (EAIS), the West Antarctic Ice Sheet (WAIS), and the Antarctic Peninsula Ice Cap (APIC) -- into a unified theory. Among these systems may be found differences in ice volume, substratum elevation, ice-surface elevation, and latitude.

Various lines of evidence do show, however, that the extent of ice in all three ice sheets has undergone significant retreats and advances. Future episodes appear inevitable. But exactly how and why the ice has fluctuated is not certain. According to one line of reasoning, the land-based EAIS has been relatively stable, experiencing only minor fluctuations since forming in the middle Miocene. By contrast, the marine-based WAIS has been dynamic, waxing and waning frequently since the late Miocene. A conflicting hypothesis has the ice sheets advancing and retreating at about the same time.

Building on previous seismic-stratigraphic investigations of the continental shelves, this group uses high-resolution seismic technology to focus on the frequency and phase of extreme advances of the ice sheets to the continental shelf. The data suggest seversl useful scientific inquiries:

First, Did extreme advances of the EAIS and WAIS occur across the shelf occur at about the same times and frequencies? This evaluation is possible because the EAIS drains into the western Ross Sea continental shelf (Northern Basin), while the WAIS drains into the eastern Ross Sea (Eastern Basin). Existing regional grids of high-resolution seismic data have been collected but these are incomplete and cannot be used to determine the stratigraphic correlations from the Northern Basin to the Eastern Basin. Project team members plan to collect high-resolution seismic data (approximately 2,000 line-kilometers) to address this issue.

Second, Did the APIC advance frequently across the shelf? Some investigators have inferred that the APIC advanced across the continental shelf at least 30 times since the middle Miocene. If true, that activity would be an order of magnitude more frequent than advances of the EAIS and WAIS. Others interpret the seismic reflections differently and argue that the advances of the APIC were far fewer. The existing high-resolution seismic grids from the Antarctic Peninsula contain only one regional strike line on the outer continental shelf. Project team members plan to collect high-resolution seismic data (approximately 1,000 line-kilometers) during their science cruise in the Antarctic Peninsula.

Integrated into the project is a graduate-level course at Louisiana State University and an a pilot outreach program with a public high school. Responding to scientific standards the Louisiana Department of Education has recently adopted to reflect what ninth through twelfth grade students should be able to do and learn, this project team will frame an experience to convey the excitement of conducting scientific research as a way to encourage students to pursue earth science at the university level.


Field Season Overview:
Researchers will use single and multi-channel seismic acquisition systems and multibeam sonar to evaluate the temporal relationships between East Antarctic and West Antarctic Ice Sheet expansion. Daily weather information from the onboard satellite systems will be used to help plan the activities around foul weather and ice conditions. In addition to the acquisition of seismic data, the researchers plan to conduct grab sampling and piston coring.