2002-2003 Science Planning Summary

Geology & Geophysics

Dr. Scott Borg
Program Manager

GO-053-O

NSF/OPP 97-26139
Station: McMurdo Station
RPSC POC: Curt LaBombard
Research Site(s): Dry Valleys

Stability of land surfaces in the Dry Valleys: Insights based on the dynamics of sub-surface ice and sand-wedge polygons
Dr. Bernard Hallet
Dr. Ronald Sletten
University of Washington
Department of Quaternary Studies

Deploying Team Members: Jennifer Horwath . Ronald S Sletten
Research Objectives: The dynamic nature of climate has received more public attention as concerns grow about warming and the recent occurrence of seemingly extreme weather events. In this context, understanding the inherent variability of Earth's climate and how humans can and do affect the environment, is becoming increasingly important. This project focuses on the landscape features and soils of Antarctica's dry valley region to provide a more complete understanding of past climatic and environmental conditions.

One important means of improving our understanding of the planetary climate system is to examine its past behavior, using the Earth as a natural laboratory. One of the most extreme changes in the climate system during the last few million years was the transition from a warm period in the Pliocene to an ice-age world. Scientists believe that during this interval relatively mild conditions in Antarctica gave way rapidly to intense glacial conditions, catalyzing the growth of what has become the largest ice sheet on Earth. This inference is based on geologic indicators of past climate, from which some scientists suggest that East Antarctica was relatively warm and largely free of glaciers about 3 to 4 million years ago (during parts of the Pliocene). The mild conditions ended abruptly, with rapid ice-sheet growth and development of the very cold, dry climate that now characterizes this region. A contrasting view, based on substantial geologic evidence, suggests that East Antarctica has been cold and the ice sheet stable for at least 8 million years, and perhaps considerably longer. These views lead to drastically different interpretations of the stability of Earth's climate.

This project's goal is to help resolve this important dilemma by introducing independent new evidence and insights derived from studies of the stability of ground ice and land surfaces in the McMurdo Dry Valleys of Antarctica. The researchers will study modern-day processes that have important implications for understanding the occurrence of buried ice found recently in Beacon Valley. This specimen may be the oldest ice on Earth. If so, it will provide strong evidence of long-term stability of the East Antarctic Ice Sheet, and may also afford a rare glimpse into atmospheric conditions millions of years ago. Specific processes to be investigated include:

Exchange at the ground surface that affects ground temperature,

Water-vapor transport and other processes leading to the formation or loss of ice in the soil, and

Frost cracking due to contraction during rapid cooling of the frozen ground in the winter, and resulting disruptions of the soil.


Field Season Overview:
The researchers plan to study the polygon dynamics, water and energy balances of soils. They will travel by helicopter from McMurdo Station to Beacon Valley where they will take samples from a massive ground ice deposit along the Onyx River in the Wright Valley that became exposed during the summer of 2001-2002.

The team members will return to McMurdo Station via helicopter and work in the Crary laboratory to process samples for return to their home institution.