Bergstrom, Anna 1 ; Koch, Joshua 2 ; O'Neel, Shad 3
1 University of Colorado - Boulder
2 U.S. Geological Survey, Anchorage, AK
3 U.S. Geological Survey, Anchorage, AK
Rapid ice loss characterizes temperate glacier regions worldwide, with wide-reaching impacts ranging from infrastructure and tourism to ecosystem services. Conceptual linkages and feedbacks between glaciers and their ecosystems exist, but observations and theory to robustly describe the processes linking the physical and biological systems remain poorly resolved. In particular, we have limited understanding of how glacier change will be reflected in the relative contributions from different water sources (i.e. snow and ice melt, rain, and groundwater) and how the biogeochemical signature associated with changing magnitude of each source contribution will be altered.
We address these issues using an end member mixing analysis method in the Wolverine Glacier watershed located in southcentral Alaska’s Kenai mountains. Wolverine Glacier is part of the United States Geological Survey Benchmark Glacier Project, a long-term glacier mass balance monitoring effort. During 2016, USGS coupled an integrated ecosystem study designed to link ecosystem-level changes with ice mass loss to the long-term efforts. Here we report initial results of spatially and temporally distributed water samples collected from a wide range of water sources within the Wolverine watershed, paired with samples taken at the river delta of the larger watershed near the ocean. We identified the main water sources and tracers to constrain end members in a mixing model. This mixing model was applied at four times through the summer season to identify how the relative contributions of each source evolves through snowmelt, the summer dry down, and late season rains. We found that the watershed is dominated by snow and glacial melt, which will gradually decline over longer time scales. We hypothesize that in the future, early season streamflow will resemble the mixture we currently observe in late season - a more rain and groundwater dominated signal with an exacerbated summer dry down signal due to lack of glacier melt sustaining streamflow. This change in the stream biogeochemical signal can have large ecosystem impacts by shifting nutrient availability and quality.