Study of Taylor Glacier Terminus
Bernard Hallet (University of Washington) and Andrew Fountain (Portland
Sate University) plan a comprehensive study of land-based polar
ice cliffs. Through field measurements and modeling they will identify
the physics underlying the formation of ice cliffs at the margin
of Taylor Glacier in the McMurdo Dry Valleys. They will explore
such questions as: Why do cliffs form? Why are ice cliffs ubiquitous
in certain areas and absent in others? What is the effect of a terminal
lake on the stress distribution? and What are the details of the
calving process? On a global scale, this work will provide insight
into the fundamental processes of calving and glacier terminus evolution
that will shed light not only on other land- and water-based glacier
termini on Earth, but also possibly on the cliff- and terrace-like
features of the Martian ice caps. Moreover, a better grasp of ice
cliff processes will improve boundary conditions required for predicting
glaciers' response to climate change.
At three sites the field team, led by Erin Pettit, will measure
the ice deformation and temperature fields near the cliff face using
a combination of strain gages, tilt sensors, thermistors and a GPS
surface strain network. An ablation stake network will augment existing
energy balance data and a small seismic network will monitor local
"ice quakes" associated with ice cracking at the terminus
and calving events. These data will be combined with time lapse
photography to document ice cliff evolution. Ultimately, the field
data will be used to test and validate a computer model that will
then be able to explore the sensitivity of ice cliff evolution to
diverse glacier characteristics.
In the 2004-05 field season ICDS will drill 3 holes to the bed (30-80
m) at each of 3 sites, two near the ice cliffs and one about 200
m upstream. The holes will be instrumented with an array of strain
gages to measure borehole deformation throughout the year. Ice temperature
will be measured using a thermistor string in boreholes at each
site, one within 5 m of the cliff face (if it turns out to be possible
to drill that close) to measure the penetration of the seasonal
temperature cycle and one 10 to 20 meters upstream to measure the
average temperature profile. Ice samples from the borehole drilling
and from the cliff face will be analyzed for impurity content and
grain size, and, ideally, preferred crystal orientation.
A 3" Eclipse drill will be used by drillers Louise Albershardt
and John Robinson.
Additional Information on this project and on McMurdo Dry Valleys
Research can be fount at:
http://www.glaciers.pdx.edu/
(Portland State Glaciology Web Site)
http://faculty.washington.edu/epettit/IceCliffs/IceCliffProject.html
(University of Washington Project Web Site)
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