2002-2003 Science Planning Summary

Glaciology

Dr. Julie Palais
Program Manager

IU-311-O

NSF/OPP 98-14589
Station: McMurdo Station
RPSC POC: Kirk Salveson
Research Site(s): Traverse from Byrd Surface Camp to South Pole

U.S. ITASE: High resolution radar profiling of the snow and ice stratigraphy beneath the ITASE traverses
Dr. Steven Arcone
Cold Regions Research and Engineering Laboratory
Steve.A.Arcone@erdc.usace.army.mil

Deploying Team Members: See U.S. ITASE Management (IU-153-A)
Research Objectives: Ice core measurements provide historical profiles of snow accumulation and chemistry at only the point where the core was drilled every 100 kilometers along the U.S. ITASE traverses. Subsurface radar, by contrast, provides reflection profiles of continuous horizons, generally related to density and chemistry contrasts. However their continuity strongly suggests that they are isochronal (demonstrate regularity of period). Thus, they can be used to track particular years between core sites and to provide a broad and more meaningful average of year-to-year accumulation rates, given the time versus depth calibrations from the cores.

This project is tracking these reflection horizons between core sites using high-resolution ground-penetrating, short-pulse radar. The main antenna system uses a pulse centered near 400 MHz, which provides vertical resolution of about 35 centimeters and records reflections from a depth in firn of about 60 meters. During the first year of U.S. ITASE, this group tracked some horizons for distances of more than 190 kilometers and found depth variations as great as 22 meters over a 5 kilometer stretch. The variations are caused by surface topography, which affects local accumulation rates and ice movement.

This group also uses a wide range of frequencies (as high as 10 GHz and as low as 100MHz to distinguish between conductivity and density as a cause of the reflections. The horizon tracking develops spatially averaged, historical accumulation rates. These can be correlated with GPS data to find the effects of topography upon local accumulation rates. The radar is also used for advanced crevasse detection for the traverses.


Field Season Overview:
The ITASE project team and support contractor staff traverse West Antarctica from Byrd Surface Camp (BSC) to South Pole Station. Two trains pulled by Challenger 55 Caterpillar tractors will transport personnel, instruments, and field camp equipment. Along the way, team members will collect ice cores and surface snow and ice samples, take meteorological readings, and collect radar profiles of the ice sheet. Periodically, Twin Otter aircraft will resupply the traverse team and transport samples back to Byrd Surface Camp. At the end of the traverse, the group will return to McMurdo Station where they will begin to analyze some of their samples. Other samples will be returned to their home institutions.