2002-2003 Science Planning Summary


Dr. Julie Palais
Program Manager


NSF/OPP 00-86297
Station: McMurdo Station
RPSC POC: Joni English
Research Site(s): Onset D

Characterizing the onset of ice stream flow: A ground geophysical program
Dr. Sridhar Anandakrishnan
Pennsylvania State University
Department of Geosciences and Environment Instit

Deploying Team Members: Sridhar Anandakrishnan . Peter Braddock . Irina Filina . Robert W Greschke . Bruce Long . Matthew A Nolan . Leo E Peters . Andy M Smith . Donald E Voigt . Paul Winberry
Research Objectives: Ice streams of the Ross Sea Embayment are the principle force by which the interior West Antarctic Ice Sheet (WAIS) is drained, moving vast quantities of ice rapidly to the front of the Ross Ice Shelf where they are calved off as icebergs. These ice streams provide a buffer between the interior ice and the floating ice shelves. For antarctic ice streams on the Siple Coast, the transition from no-sliding (that is, all internal deformation) to motion dominated by sliding is defined as the "onset-region." To fully understand and adequately model the WAIS, scientists need a better understanding of this onset region, which means learning the reasons for their fast flow and the factors controlling their current grounding-line, margin and head positions. The lateral margins of the ice streams are also a transition that needs better explanation.

Hypotheses on controls of the location of the onset region range from the "purely-glaciologic" to the "purely-geologic." Ice sheet models will remain incomplete until the basal boundary conditions (roughness, wetness, till properties) are specified and a good subglacial geologic map that shows the distribution, thickness, and properties of the sedimentary basins is drawn.

These parameters can be estimated from seismic, radar, and other geophysical methods. This group will study the transition region of ice stream D in detail with this coupled geophysical experiment. They will select other locations on ice streams C & D to study, compare, and contrast conditions with the main site on ice stream D. Site-selection for the main camp will be based on existing radar, GPS and satellite data, as well as input from the modeling community.

Field Season Overview:
Project team members will travel by LC-130 aircraft to the Onset D Camp in Marie Byrd Land. Traveling from the camp on tracked vehicle and snowmobile, they will conduct GPS surveys and shallow and deep radar profiling of the ice along primary survey lines.

Team members will travel by Twin Otter aircraft to satellite locations on ice streams C and D. Using tracked vehicles and snowmobiles, they will conduct additional GPS surveys and radar profiles and collect additional firn cores

The field team will install geophones to record seismic data generated by detonations that will take place in 600 boreholes drilled by Ice Core Drilling Services (ICDS, TO-150-M/S) near Onset D camp and in 150 boreholes drilled by researchers at the satellite camps.