Characterizing the Onset of Ice Stream Flow: A Ground Geophysical Field Program

Project Description
This award supported a four year project to develop of better understanding the
ice streams of the Ross Sea Embayment (A--F) which drain the interior West
Antarctic Ice Sheet (WAIS) by rapidly moving vast quantities of ice to the
calving front of the Ross Ice Shelf. The project examined the role of these ice
streams as buffers between the interior ice and the floating ice shelves. The
reasons for their fast flow, the factors controlling their current
grounding-line-, margin-, and head-positions are crucial to any attempt at
modeling the WAIS system and predicting the future of the ice sheet. For the
Antarctic ice streams of the Siple Coast, the transition from no-sliding (or
all internal deformation) to motion dominated by sliding is defined as the
"onset-region". To fully understand (and adequately model) the WAIS, this onset
region must be better understood. The lateral margins of the ice streams are
also a transition that need better explanation. Hypotheses on controls of the
location of the onset region range from the "purely-glaciologic" to the
"purely-geologic. Thus, to model the ice sheet accurately, the basal boundary
conditions (roughness, wetness, till properties) and a good subglacial geologic
map, showing the distribution, thickness, and properties of the sedimentary
basins, are required. These parameters can be estimated from seismic, radar,
and other geophysical methods. The transition region of ice stream D was
studied in detail with this coupled geophysical experiment. In addition,
selected other locations on ice streams C & D were made, in order to compare
and contrast conditions with the main site on ice stream D. Site-selection for
the main camp wasbased on existing radar, GPS, and satellite data as well as
input from the modeling community.