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I'm a Ph.D candidate in the
glaciology group of the
Department of Earth and Space Sciences of the University of Washington,
Seattle. My CV has
more details.
Research:
- Ice-sheet radar attenuation
Understanding the
relationship between ice chemistry, temperature and radar attenuation
is important for studies of echo intensities in ice-sheet radar data.
Radar attenuation is often poorly constrained but it must be estimated
to calculate the reflectivity of an ice-sheet bed, which is diagnostic
of frozen/thawed basal conditions. In collaboration with others at
the University of Washington, we have synthesized an ice-conductivity
model that uses ice chemistry and temperature data to calculate radar
attenuation. This model has been applied to Siple Dome, West Antarctica using
ice-core and radar data.
MacGregor, J.A., D.P. Winebrenner, H. Conway, K. Matsuoka,
P.A. Mayewski and G.D. Clow, 2007, Modeling englacial radar
attenuation at Siple Dome, West Antarctica, using ice chemistry and
temperature data,
Journal of Geophysical Research, 112, F03008. pdf
Matlab scripts and functions for modeling
ice-sheet radar-attenuation rates
We will next use this attenuation model to analyze radar data
collected above Subglacial Lake
Vostok, East Antarctica, and the Ross ice streams in West
Antarctica. Both of these regions have unusual ice-bed interfaces
compared to the rest of the inland ice sheet. There is both melting
and accretion
of ice occurring over Lake Vostok, and its spatial distribution may
further influence the dynamics of the ice-sheet flow over the lake.
The soft and sometimes water-saturated marine sediment that appears to
underlie most of the Ross ice streams leads to basal sliding and fast
flow speeds. We will use the attenuation model to match observed
attenuation rates and predict their spatial variation so that bed
reflectivities, and hence basal conditions, can be more reliably
determined.
- Detection of weak radar layers
Matched filtering
and sloped lateral averaging can improve detection of weak radio
echoes that might otherwise go unnoticed in a radargram. In
collaboration with others at the University of Washington, we have
applied these algorithms to radar data from the Siple Coast region of
West Antarctica.
- Origin of anomalous volcanic signals in ice
cores
Most chemical signals of volcanic eruptions detected
in ice cores are primarily sulfuric acid peaks. However, a prominent
radar layer in West Antarctica is correlated with a volcanic
signal that is dominated by hydrochloric and hydrofluoric acids. I
investigated possible causes of this anomalous signal.
- Evolution of water-filled crevasses
Surface melting
may cause faster basal sliding in Greenland via crevasses that
penetrate the ice sheet all the way to its bed. I investigated how
quickly water-filled crevasses could reach the bed by combining a
static crevasse model based on fracture mechanics with a
time-dependent model for crevasse growth. My results suggest that
completely water-filled crevasses can easily penetrate to the bed
within one melt season.
- Radar polarimetry in inland West Antarctica
This
project is run by Kenichi
Matsuoka. The goal of this project is to study ice fabrics and
strain patterns near the site of upcoming deep ice core at the
Ross-Amundsen Sea ice divide in West Antarctica. I participated in
the fieldwork for the project 2005-2006 field season (link to photos
below).
- Beach ridge evolution using ground-penetrating
radar
On Sitkalidak Island in the Kodiak Archipelago, I
used ground-penetrating radar to look at the progradational
morphologies of paleo and modern beach ridges. This work was done in
conjunction with several University of Washington geologists and the
University of Washington Archaeological Field School.
Committee:
Background:
I graduated from Colorado School of
Mines in May 2002 with a B.S. in geophysical
engineering. My focus as an undergraduate was applied geophysical
methods (e.g., seismics to find oil and
gas or magnetics to find unexploded
ordnance). I first became interested in glaciology while climbing and reading books
like
South,
An Alien in Antarctica and especially
Glacier Ice; I first became interested in ice-penetrating radar while
examining the quality of the
radar profiles collected by other
University of Washington glaciologists.
Photos:
Last updated: 03/2008
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