Why Do Glaciers Surge? Understanding the Last Eight Surges of Donjek Glacier, Yukon, Canada
Glacier surges are short periodic episodes of rapid glacier flow that are driven by internal instabilities and bracketed by longer periods of slow flow. These glaciers are important to understand because they are vital to predicting future sea level rise, mitigating glacier hazards, and understandin...
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DigitalCommons@UMaine
2019
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| Online Access: | https://digitalcommons.library.umaine.edu/etd/3103 https://digitalcommons.library.umaine.edu/context/etd/article/4180/viewcontent/Kochtitzky_thesis_final_5.14.2019.pdf |
| Summary: | Glacier surges are short periodic episodes of rapid glacier flow that are driven by internal instabilities and bracketed by longer periods of slow flow. These glaciers are important to understand because they are vital to predicting future sea level rise, mitigating glacier hazards, and understanding basal glacial processes. Donjek Glacier, located in the Yukon, Canada has an unusually short and regular surge cycle, with eight surges identified since 1935 from aerial photographs and satellite imagery with a ~12 year repeat interval and ~2 year active phase. Recent surges occurred during a period of long-term negative mass balance and cumulative terminus retreat of 2.5 km since 1874. In contrast to previous work, we find that the constriction where the valley narrows and bedrock lithology changes, 21 km up-glacier of the terminus, represents the upper limit of surging, with negligible surface speed or elevation change up-glacier from this location. This positions the entire surge-type portion of the glacier in the ablation zone. The constriction geometry does not act as the dynamic balance line, which we consistently find at 8 km up-glacier from the glacier terminus. During the 2012–2014 surge, the average lowering rate in the lowest 21 km of the glacier was 9.6 m a-1, while during quiescence it was 1.0 m a-1. Due to reservoir zone refilling, the ablation zone has a positive geodetic balance in years immediately following a surge event. An active surge phase can result in a strong negative geodetic mass balance over the surge-type portion of the glacier. Potential links between climate and glacier surges are not well understood, but are required to enable prediction of glacier surges and mitigation of associated hazards. This thesis investigates the role of snow accumulation and atmospheric temperature on surge periodicity, glacier area changes, and surge initiation since the 1930s for Donjek Glacier. Three ice cores from Eclipse Icefield, at the head of the glacier, indicate that a total accumulation of 13.1 to ... |
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