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MS Thesis Defense
Tiffany Gatesman (Department of Chemistry and Biochemistry | Water and Environmental Research Center, UAF)
When: Tuesday, April 4 at 12pm/Noon (AKST)
Where: Duckering 531
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Abstract: Glacier melt affects the geochemical composition of many sub-arctic and alpine rivers; however, quantifying the melt contribution to larger-scale watershed runoff has attracted limited attention. To estimate glacier contribution, we conducted a 6-year geochemical hydrograph separation study in a geologically heterogeneous alpine glacial watershed in subarctic Interior Alaska.
Water samples were collected daily from Jarvis Creek (534 km2, 3% glacier coverage) at the base of the watershed, and source waters were collected annually from rain, snow, highland winter baseflow, and glacier terminus and were analyzed for stable water isotopes and dissolved ions.
Stream surface water samples show large seasonal and inter-annual geochemical variation. Source waters show distinct chemical signatures allowing the use of a geochemical hydrograph separation model. Considerable inter-annual differences among source water signatures emphasize problems in the assumption of using select defined geochemical signatures for multiple-year use.
Over the 6 years studied, we estimated a seasonal average of 35% glacier contribution with a daily range of 2-80% with minimum percentage contribution in May and maximum in September. Inter-annual and seasonal variation in meteorology, streamflow, watershed geochemistry and estimated source contributions suggests that glacial melt contribution is dependent on local and regional climatic conditions.
Based on glacier runoff projections by others and our hydrograph separation results, we estimate that future stream discharge by the end of the century will reduce by 48% in dry years and 22% in wet years.