Collaborative Research: Present and future contribution of glacial runoff to freshwater discharge into the Gulf of Alaska

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Freshwater influx to the Gulf of Alaska (GOA) is strongly influenced by glacier runoff as roughly one fifth of its drainage basin is covered by glacier ice. During the last decades GOA glaciers have generally thinned and retreated and hence precipitation stored in the glaciers as snow and ice has been released augmenting streamflow and freshwater influx to the Gulf of Alaska. Glaciers draining to the GOA are highly sensitive to climate warming and mass loss rates are expected to increase. It is hypothesized that runoff from glaciers will initially increase by more than 50% as wastage accelerates, but then will reach a turning point upon which runoff will decrease as the glaciers shrink and partly disappear. Hence, the changes in the hydrological cycles due to glacier wastage are substantially larger than expected changes in any other component of the water budget in this region.The research will quantify these changes in runoff. A glacier runoff model is used to simulate the current magnitude and timing of runoff from glaciers that drain to the Gulf of Alaska and project how glacial runoff along the Gulf of Alaska will change by 2100 in response to future climate scenarios in Alaska downscaled by a high resolution regional climate model. Further, potential changes to the biogeochemical fluxes into freshwater and marine ecosystems associated with the projected changes in glacier runoff are assessed. Results provide regional scale estimates of glacier runoff changes and associated impacts on biogeochemical fluxes for the GOA. A modeling strategy is developed that can be used to evaluate glacier runoff changes and hydrologic ?tipping points? in other heavily glacierized regions. Moreover, the downscaled climate scenarios we develop will be available for other impact studies. Visualization products of the results are made available to the Mendenhall Glacier visitor center, which is visited by approximately 350,000 people each year.