Date of Award

Fall 12-15-2023

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

Lee Karp-Boss

Third Committee Member

Emmanuel Boss

Abstract

The Greenland Ice Sheet has undergone rapid mass loss over the last four decades, primarily through solid and liquid discharge at marine-terminating outlet glaciers. The acceleration of these glaciers is in part due to the increase in temperature of ocean water in contact with the glacier terminus. However, quantifying meltwater injection and heat transport can be challenging due to iceberg abundance, which threatens instrument survival and fjord accessibility. Additionally, acceleration and eventual retreat of tidewater glaciers onto land can change glacier forcing, completely altering fjord water-meltwater dynamics. Here, we couple in situ and remote sensing methods to quantify the upper-layer fjord dynamics in two critical regions in Greenland. In the summers of 2014 and 2019, we deployed transmitting GPS units on a total of 13 icebergs in Ilulissat Icefjord to quantify upper-layer (0 – 250 m) circulation. In the summers of 2022 and 2023, we collected 147 suspended sediment concentration measurements in fjords abutting glaciers that are in various stages of retreat. We use the suspended sediment record in south Greenland fjords to quantify surface suspended sediment load in fjords, which is generally positively correlated with meltwater runoff. Overall, we find that glacier meltwater runoff strongly impacts upper-layer fjord circulation, suspended sediment concentrations, and that glacier behavior is directly related to meltwater runoff. More specifically, we find that the direction of upper-layer fjord circulation is strongly impacted by the timing of meltwater pulses, while the circulation speed changes in concert with tidewater glacier behavior (i.e., increases and decreases in glacier speed and meltwater runoff). In fjords with retreating tidewater glaciers, we find that increases in suspended sediment concentration at the fjords surface is directly related to the timing of meltwater pulses and glacier retreat. Suspended sediment concentration in a transitioning fjord environment is increasing over a decadal period, and likely will continue to increase, coupled with tidewater glacier retreat, in other locations in light of atmospheric and oceanic warming. This study demonstrates the utility of remote sensing methods, specifically glacier and surface reflectance, to constrain upper-layer fjord dynamics in changing Greenlandic glacier environments.

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