Glaciers in the Earth system: an evaluation of the causes and effects of glacier change in southern Patagonia and beyond
2022-04
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Glaciers in the Earth system: an evaluation of the causes and effects of glacier change in southern Patagonia and beyond
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2022-04
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Glaciers do not exist in isolation: they interact with the surrounding Earth System across a wide range of temporal and spatial scales. Global glacier recession driven by anthropogenically forced global warming has both intensified many of the interactions between glaciers and their surroundings and highlighted their importance. Glacier-ocean interactions are one well-known and globally important example, considering that unstable marine-terminating portions of Greenland and West Antarctica hold several metres of potential sea-level rise. However, other important interactions, such as between glaciers and ice-contact lakes, remain largely unexplored. Likewise, a wide suite of connections between glaciers and the surrounding Earth System can influence, and are impacted by glacier change. This thesis explores these interactions with the objective of contributing to a new integrated view of glaciers in the Earth System. The twenty-first century has both highlighted the need to understand glacier retreat and provided scientists with powerful new tools to analyze our cryosphere. In this thesis, I assess the drivers of glacier change by combining high-resolution satellite imagery, lake sediment cores, and field data with numerical modelling. Southern Patagonia is an ideal natural laboratory to examine the interactions between glaciers and the surrounding Earth System, due to its extensive glaciation, high relief, large proglacial lake systems, and extreme climate gradients. We also include two other study locations, the Northern Andes and Uttarakhand Himalaya, in which glacier change has created new geohazards and water security challenges for nearby populations. We find that large ice-contact lakes preserve an high-resolution record of climatic and glacial changes. We identify annual-resolution sediment layering ('varves') in Lago Argentino, the world's largest ice-contact lake, and use this to investigate the dominant controls on sedimentation across the lake. We show that, at Lago Argentino, varves are formed due to seasonal variations in glacial and fluvial sediment fluxes along with a seasonal cycle in lake mixing. In addition, we demonstrate that the dominant climatic controls on sedimentation are summer temperature and wind speed. On a larger scale, we use Lago Argentino's sedimentary record to identify a high late-Holocene eruption rate at the nearby Andean Austral Volcanic Zone, and dominant 200, 150, and 85 year periodicities in the high-latitude Southern Hemisphere's dominant mode of climatic variability, the Southern Annular Mode. Next, we investigate the interactions between glaciers and two major natural hazards: landslides and volcanic eruptions. For the former, we show that landslides can induce extensive and long-lasting effects on glaciers, with a 0.25 km^3 landslide reversing the multi-decadal retreat trend of a Patagonian tidewater glacier. For the latter, we identify a ~75% greater eruption rate in times of low ice volume in Southern Patagonia, due to deglaciation-induced tensional upper-crustal stresses. This process may affect other ice-clad volcanoes around the world. Glaciers can also contribute to major disasters, of which the deadly Chamoli rock-ice avalanche in February 2021 is a devastating example. We combine several advanced remote sensing methods to investigate the pre-collapse conditions of this avalanche, and show that the landslide was mobile more than five years prior to its February 2021 collapse. We also use a newly developed glacier velocity-based method to calculate the thickness and volume of all glaciers in the Northern Andes, where volcano-ice interactions initiated the worst volcanic disaster of the past 100 years. These ice-thickness maps will enable future research to identify zones most vulnerable to glacier-related hazards, and map out future water-resource vulnerabilities. Overall, our results highlight the importance of integrative and collaborative studies for forecasting the future of the world's glaciers, and their impacts on nearby populations.
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University of Minnesota Ph.D. dissertation. April 2022. Major: Earth Sciences. Advisors: Andrew David Wickert, Emi Ito. 1 computer file (PDF); xiv, 405 pages.
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Van Wyk de Vries, Maximillian. (2022). Glaciers in the Earth system: an evaluation of the causes and effects of glacier change in southern Patagonia and beyond. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/241337.
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