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Collaborative Research:
Lithospheric Controls on the Behavior of the West Antarctic Ice Sheet:
Aerogeophysics of the Eastern Ross Transect Zone
Principal Investigators: Don Blankenship, Robin Bell, and Carol Finn
Funding agency: National Science Foundation award #9319369
Start Date: August 1, 1994
Expires: July 31, 1999 (estimated
Abstract
This award supports a project to conduct an integrated geophysical survey over a large portion of
the West Antarctic Ice Sheet (WAIS) toward an understanding of the dynamic behavior of the ice sheet
and the nature of the lithosphere beneath the ice sheet. West Antarctica is characterized by two kinds
of the Earth s most dynamic systems, a continental rift (the West Antarctic Rift System) and a marine
based ice sheet (the WAIS). Active continental rift systems, caused by divergent plate motions, result
in thinned continental crust. Associated with the thin crust are fault-bounded sedimentary basins,
active volcanism, and elevated heat flow. Marine ice sheets are characterized by rapidly moving streams
of ice, penetrating and draining a slowly moving ice reservoir. Evidence left by past marine ice sheets
indicates that they may have a strongly non- linear response to long-term climate change which results
in massive and rapid discharges of ice. Understanding the evolution of the ice stream system and its
interaction with the interior ice is the key to understanding this non-linear response. Subglacial
geology and ice dynamics are generally studied in isolation, but evidence is mounting that the behavior
of the West Antarctic ice streams may be closely linked to the nature of the underlying West Antarctic
rift system. The fast moving ice streams appear to glide on a lubricating layer of water-saturated
till. This till requires easily eroded sediment and a source of water, both of which may be controlled
by the geology of the rift system; the sediments from the fault-bounded basins and the water from the
elevated heat flux associated with active lithospheric extension. This project represents an
interdisciplinary aerogeophysical study to characterize the lithosphere of the West Antarctic rift
system beneath critical regions of the WAIS. The objective is to determine the effects of the rift
architect ure, as manifested by the distribution of sedimentary basins and volcanic constructs, on the
ice stream system. The research tool is a unique geophysical aircraft with laser altimetry, ice
penetrating radar, aerogravity, and aeromagnetic systems integrated with a high precision kinematic
GPS navigation system. It is capable of imaging both the surface and bed of the ice sheet while
simultaneously measuring the gravity and magnetic signature of the subglacial lithosphere. Work to be
done under this award will build on work already completed in the southern sector of central West
Antarctica and it will focus on the region of the Byrd Subglacial Basin and Ice Stream D. The ice sheet
in these regions is completely covered by satellite imagery and so this project will be integrated with
remote sensing studies of the ice stream. The changing dynamics of Ice Stream D, as with other West Antarctic
ice streams, seem to be correlated with changes in the morphological provinces of the underlying rift system.
The experimental targets proceed from the divide of the interior ice, downstream through the onset of
streaming to the trunk of Ice Stream D. This study will be coordinated with surface glaciological
investigations of Ice Stream D and will be used to guide cooperative over-snow seismic investigations
of the central West Antarctic rift system. The data will also be used to select a site for future deep
ice coring along the crest of the WAIS. These data represent baseline data for long term global change
monitoring work and represent crucial boundary conditions for ice sheet modeling efforts.
Schematic of the West Antarctic ice sheet and its
lithospheric setting. The interior ice reservoir is the portion of the ice sheet below the
ice divide where the ice sheet is attached to its bed. This interior ice is penetrated and
drained by the fast moving ice streams which flow between regions of relatively stagnant
ice. The open arrows indicate the gliding of ice over its bed from the onset region toward
the ice shelf. Beneath the ice streams the lubricating till is illustrated. The
extensional nature of the underlying lithosphere is indicated by the sediment filled
grabens beneath the ice streams.
Active WAIS-related projects at the University of Texas at Austin include:
Onset of Ice Stream Flow
Western Divide West Antarctic Ice Cores (WAISCORES) Site Selection
Previous WAIS-related projects at the University of Texas at Austin include:
Support Office for Aerogeophysical Research
Advanced Technology for Radar Sounding
CASERTZ
WAISCORES Inland Site Selection
WAIS Ice Divide Migration
Links to other WAIS pages:
WAIS Homepage
at NASA Goddard Space Flight Center
WAISCORES page at Desert
Research Institute, University of Nevada, Reno
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