Degree
Doctor of Philosophy (PhD)
Department
Geology & Geophysics
Document Type
Dissertation
Abstract
Taylor Valley, which opens to the Ross Sea, is one of several ice-free valleys comprising the McMurdo Dry Valleys, Antarctica. The valley is home to several close-basin, perennially ice-covered lakes, whose lake levels largely reflect a balance between meltwater inputs and lake ice ablation; both being driven by climate. A dynamic environment exists where the lake ice covers meet the lakeshore, with the ice grounding to the substrate throughout the cold and dark of winter, and melting to form a perimeter of thin-to-no ice around the lake during the summer. These marginal freeze-thaw regions are known as moats. Here, physical, chemical, and biological components of the moat of Lake Fryxell in Taylor Valley are investigated to gain more insight into this poorly understood environment. The moat is found to be biologically and chemically distinct from the main lake, though some exchanges may occur. Thermocouple and ice-sounding measurements show that in summer, moat-ice melts from the bottom up, even in sub-freezing temperatures, and this process is dominantly driven by solar radiation. At times, moat melt breaches the surface, forming open water regions that vary in size annually. The size of the open moat is tracked via satellite imagery to establish an annual record, and an index-model is produced to extend that record. Lake level changes affect the area of the moat environment, but forecasting requires these changes to be tracked volumetrically. A sub-meter scale hypsometric curve for the shallow regions of the lake is produced to address this, and the modern volume change record casts doubt onto the validity of the hypothesized paleolake history for Taylor Valley. An extensive literature review reveals that many predominant hypotheses regarding lake and glacial history in Taylor Valley are not supported by published literature, and a revised hypothesis for valley history is presented. Cosmogenic radionuclide dates from alpine glacier moraines and ice-sheet drift, along with infrared stimulated luminescence samples from landscape features in lower Taylor Valley, support this revised hypothesis for Taylor Valley’s history.
Date
10-28-2024
Recommended Citation
Stone, Michael Stanley, "Modern Lakeshore Processes and Historic Lake and Glacial Changes in Taylor Valley, Antarctica" (2024). LSU Doctoral Dissertations. 6611.
https://repository.lsu.edu/gradschool_dissertations/6611
Committee Chair
Doran, Peter T.