HR: 14:40h
AN: B43F-05    [Abstracts]
TI: The impact of changing glacial coverage on yields of freshwater and nutrients from coastal watersheds with in southeastern Alaska
AU: * Hood, E
EM: eran.hood@uas.alaska.edu
AF: University of Alaska Southeast, 11120 Glacier Highway, Juneau, AK 99801, United States
AU: Scott, D
EM: dtscott@unl.edu
AF: University of Nebraska-Lincoln, 214 Bessey Hall, Lincoln, NE 68502, United States
AB: Glaciers in southeastern Alaska are particularly sensitive to climate change because of their low elevation and proximity to the coast. Currently, glaciers in this region are experiencing high rates of ice loss resulting in rapid thinning and retreat. We are examining how changing glacial coverage is altering fluxes of freshwater and nutrients from coastal watersheds in southeastern Alaska. Our study includes three adjacent watersheds that range in area from 37 km² to 230 km² and span a range of watershed glacier coverage from 0% to 55%. Physical and hydrochemical parameters were sampled weekly to bi-monthly for the period May 2006-April 2007 in the three watersheds. Physical measurements included temperature, suspended sediment and conductivity; and hydrochemical parameters included total and inorganic nitrogen, dissolved organic carbon, sulfate, and orthophosphate. During the glacier melt season, glacial coverage within a watershed exerted a strong influence on physiochemical properties. Streamwater temperature and conductivity, as well as nutrient concentrations, were negatively correlated with glacier coverage, while suspended sediment loads were positively correlated with glacial coverage. Changing glacial coverage had a strong impact on watershed yields of carbon, nitrogen, and phosphorus. Watershed yields of dissolved organic carbon (DOC) ranged from 4246 to 7646 kg km^-2 yr^{- 1} and were strongly negatively correlated with percent glacier coverage. Watershed yields of dissolved inorganic nitrogen ranged from 180 to 498 kg km^-2 yr^-1 and were highest in the watershed with intermediate glacier coverage that has a high proportion of transitional nitrogen fixing plant species. Watershed yields of orthophosphate ranged from 19 to 46 kg km^-2 yr^-1 and were strongly positively correlated with glacier coverage. Our findings suggest that the magnitude and timing of freshwater and nutrient fluxes from coastal watersheds to receiving marine ecosystems will be altered dramatically as glaciers in southeastern Alaska continue to decrease in volume. In addition, we hypothesize that changes in nutrient fluxes are mediated both by two basic factors: 1) changes in landcover associated with glacial recession and 2) changes in biological activity in riverine systems resulting from decreased inputs of glacial meltwater as glaciers continue to recede.
DE: 0400 BIOGEOSCIENCES
DE: 0483 Riparian systems (0744, 1856)
DE: 0496 Water quality
DE: 0720 Glaciers
DE: 0740 Snowmelt
SC: Biogeosciences [B]
MN: 2007 Fall Meeting