Date of Award

Summer 8-20-2021

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Kristin M. Schild

Second Committee Member

Seth Campbell

Third Committee Member

Peter Koons

Abstract

The amount of ice stored in Antarctica has the potential to raise sea level by almost 60 meters. Mass is primarily lost through glaciers draining the ice sheet and flowing into and ice shelves. Ice shelves float on the ocean and act as a resisting force to the flow of the glaciers, thereby modulating the flow of tributary glaciers, and consequently glacier contribution to global sea level rise. McMurdo Ice Shelf (MIS) buttresses four tributary glaciers, three of which will be discussed in this thesis, as well as the northwest corner of the faster flowing Ross Ice Shelf, which has tributary glaciers flowing from both East and West Antarctica. McMurdo Ice Shelf also serves as a runway for planes traveling to research bases on Ross Island. Therefore, if MIS were to thin, become unstable, or collapse, the results would not only impact the rate of sea level rise, but also Antarctic science logistics. This thesis quantifies changes in surface elevation and surface velocity to better understand the relationship between MIS and its tributary glaciers. I isolated the surface elevation change resulting from accumulation and ablation, and tracked ice shelf retreat across the study region. I differenced high resolution digital elevation models (DEMs, 2011 – 2015) in the Hut Point region of Ross Island, first correcting for errors introduced in DEM processing, and then removing the tidal and atmospheric pressures across the ice shelf region. These results revealed variable elevation change across the ice shelf (± 2 m) and across the ice on Hut Point Peninsula (± 5 m) as well as ice shelf front retreat (up to 1 km). While both the ice shelf thinning and the frontal retreat contribute to the instability of MIS, the retreat is immediately concerning as it threatens to cut off Ross Island from the runways via Pegasus Road, thereby necessitating that a relocation of the road be considered. To further explore this system, I focused on evaluating velocity changes, and deriving strain rates across the glacier-ice shelf system on both seasonal and annual timescales by combining NASA velocity products with newly constructed geospatial velocity maps, utilizing Landsat imagery. These results revealed speeds as high as 225 m a-1 on the glaciers and 215 m a-1 on the ice shelf, with higher speeds occurring during the summer months. Two relationships between MIS and its tributary glaciers emerge: (1) seasonal velocity fluctuation of both the ice shelf and the tributary glacier, and (2) fluctuation of only MIS velocity and consistent velocity on the adjacent glaciers between seasons. These two relationships suggest spatial variability in the system’s driving forces, and necessitate future work focusing on resolving these drivers. Results from this thesis are the first of their kind to use remote sensing to evaluate the relationship between tributary glaciers and MIS, and bridge a gap between in situ surveys and modeling projections.

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