The West Antarctic Ice Sheet Program
(Adapted from a report edited by R. Bindschadler
of NASA Greenbelt Space Flight Center, Greenbelt, MD)
An NSF continuing project designed to answer:
1. How will the West Antarctic Ice Sheet affect future sea
level?
2. How do rapid global climate changes occur?
As the last ice sheet on Earth resting on a deep marine basin,
the West Antarctic Ice Sheet, according to ice-flow theory, is
inherently unstable. All other marine-based ice sheets collapsed
during the interglacial beginning 20,000 years ago, and the West
Antarctic Ice Sheet itself suffered a series of partial collapses.
Marine records from this period show sea level rise was punctuated
by many very rapid elevations, much faster than the rate over
the last 4000 years, probably a result of complete or partial
ice-sheet collapses.
A collapse would possibly disrupt ocean circulation patterns
and could trigger further climate change. The WAIS program is
seeking to learn what triggers marine ice-sheet collapse and evaluate
the possibility of such a calamity.
A "staggering result" from analysis of the ice core of the Greenland
Ice Sheet Project II was the conclusion that regional climate
can flip modes (glacial to interglacial) in as little as a single
year. A similar ice core from the Southern Hemisphere is urgently
needed to determine whether these rapid changes are a global phenomenon.
The only area in the Southern Hemisphere where the compressed
snow layers are thick enough to allow absolute dating of inter-annual
variations is in the interior of West Antarctica.
The ice sheet is drained by ice streams sliding on extremely
weak marine sediments deposited when no ice sheet was present.
An active rift system underlies the ice sheets, delivering heat
and melting basal ice, weakening subglacial layers and lubricating
the bed.
Huge floating ice shelves interfere with ice-stream drainage,
and the water cavity underneath circulates heat from the open
ocean. With enough heat, the ice shelves will corrode faster than
snowfall can rebuild them. If they disappear, the ice sheet could
collapse.
The West Antarctic Ice Sheet is not in a stable state at present.
Whether this is symptomatic of an impending collapse is not known.
The WAIS program, involving scientists from other countries and
other agencies, is under Dr. Julie Palais, NSF's Program Manager
for Antarctic Glaciology in the Office of Polar Programs. The
following time table for the WAIS ice-core drilling component
is anticipated:
-
Drilling a core to bedrock at Siple Dome, 1997-98
-
Three-season drilling at proposed inland ice-divide site,
1998-2000
-
Analysis of core consuming two more years
