Thesis Defense Announcement

College of Arts and Sciences announces the Final Thesis Defense of

Peter Matheny

for the Degree of Master of Science

March 29, 2019 at 11:00 AM in CERI Seminar Room, 3892 Central Ave

Advisor: Robert Smalley, Jr.

Inferring glaciological attributes of Thwaites Glacier using GPS-IR and PPP

ABSTRACT: We use two continuous GPS stations located on Thwaites glacier to estimate the rate of snow accumulation and examine details of the motions of the glacier. We use GPS interferometric reflectometry (GPS-IR) to measure the height of the snow surface relative to the GPS antenna to determine the secular and periodic rates of snow accumulation in meters of water-snow equivalent. We find an 8-year snow accumulation rate for the station Upper Thwaites (UTHW) of 0.44±0.002 m.w.e./yr and a 7-year rate for the station Lower Thwaites (LTHW) of 0.56±0.003 m.w.e./yr. Averages at both GPS sites match the European Centre for Medium-Range Weather Forecasts reanalysis accumulation rate, derived from integrated snowfall over the same period. Differences in accumulation rates from this study and others are not statistically significant; however, by using daily solutions for the lifetime of the stations, we reduce the formal error. Using precise point position (PPP) software we found daily positions that are fit using a standard linear trajectory model to estimate velocities, accelerations, and annual and semi-annual components of their motion. The motion at LTHW exhibits large deviations, a meter or more, from an SLTM consisting of uniform velocity and acceleration with annual and bi-annual periodic components. It appears that the significant, but short duration, deviations at LHTW from the SLTM are due to the 2013 draining event and subsequent initiation of refilling of subglacial lake THW124, which is very near or beneath the station. Subglacial lakes reduce the basal stress and can have powerful effects on the local deformation and behavior of the glacier.