Seasonal shifts in solute flux and water source chemistry in a coastal glaciated watershed undergoing rapid change: Wolverine Glacier Watershed, Alaska
Abstract
Glaciers around the world are rapidly losing mass, and the tight hydrologic coupling between glaciers and downstream ecosystem is resulting in widespread biophysical impacts. Glacier loss drives changes to the timing and magnitude of water delivery to downstream and nearshore ecosystems, as well as changes to biogeochemical exports, although detailed understanding of the changes remain poorly resolved. Along glacierized coastlines such as in southcentral Alaska, water transit times are short, and marine fisheries are likely to be impacted by ongoing and extensive changes to glaciers. Southcentral Alaska's Wolverine Glacier has a 50+ year record of mass balance and glaciological research, and in 2016 and 2017, we expanded research efforts to include biogeochemical sampling from a wide range of flow pathways and sources within the watershed. At present this glacier covers 60% of its gaged catchment, and drains quickly into a large river system and the nearshore ecosystem of Prince William Sound. Here we establish a relationship between electrical conductivity (EC) and streamflow at the watershed outlet combined with a local precipitation record to divide the melt season in to 4 hydroclimatic periods by which we characterize water chemistry. We defined source waters and flow paths within the watershed using EC, δ18O, and dissolved organic carbon concentration. Across hydroclimatic periods, the dominant source to river chemistry shifts, particularly between hypothesized shallow and deep groundwater sources. For each hydroclimatic period across two melt seasons we used the calcium concentration of water samples taken at the watershed outlet and calculated a calcium flux, a proxy for total solute flux due to the dominance of calcium carbonate rocks in the basin. We found that in the 2016 and 2017 season 55 and 40 percent respectively of Ca export occurred during the fall rainy season. As the watershed increasingly loses glacier mass and the climate shifts toward more rain and less snow, we expect to observe extended length of the high flux period. Combining hydroclimactic periods, source water chemical characterization, and solute fluxes provides new insight in to a rapidly changing system and creates a framework to differentiate biogeochemical impacts of glacier loss and precipitation change across a melt season.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C52B..08B
- Keywords:
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- 0702 Permafrost;
- CRYOSPHEREDE: 0736 Snow;
- CRYOSPHEREDE: 0738 Ice;
- CRYOSPHEREDE: 1847 Modeling;
- HYDROLOGY