HR: 0800h
AN: B21C-0896    [Abstracts]
TI: DOC Export from a Small Permafrost Watershed
AU: * Schuster, P F
EM: pschuste@usgs.gov
AF: U.S. Geological Survey, 3215 Marine Street, Suite E127, Boulder, CO 80303 United States
AU: Aiken, G R
EM: graiken@usgs.gov
AF: U.S. Geological Survey, 3215 Marine Street, Suite E127, Boulder, CO 80303 United States
AU: Striegl, R G
EM: rstriegl@usgs.gov
AF: U.S. Geological Survey, 3215 Marine Street, Suite E127, Boulder, CO 80303 United States
AU: Shanley, J B
EM: jshanley@usgs.gov
AF: U.S. Geological Survey, 87 State Street, Room 324, Montpelier, VT 05602 United States
AB: Approximately 13 percent of the Earth's land surface is currently underlain by permafrost, which is rapidly melting in some northern areas due to the effects of a warming climate. It is hypothesized that the resulting melt will release a large pool of sequestered organic carbon, nutrients, and metals within and from currently frozon soils. As part of a larger USGS water quality study of the 854,700 km$^{2}$ Yukon River Basin, we are conducting a focused "small-scale" study to measure and chemically characterize DOC export from the American Creek sub-watershed of the Yukon River Basin. The 160 km$^{2}$ watershed, located at $64\deg$ North in a remote region of the extreme eastern interior of Alaska, was chosen because its characteristics are generally representative of many watersheds in the Yukon River Basin. Permafrost underlying the American Creek watershed confines the hydrologic flow to interact with the shallow surficial materials. Snowmelt infiltrates into the unfrozen, organic-rich soil surface horizon and then flows laterally, down-gradient along the permafrost table in contact with the organic-rich material directly above the permafrost. DOC and discharge were measured at the watershed outlet during peak snowmelt for two consecutive years to understand how permafrost affects these variables. Maximum DOC concentrations and Specific ultraviolet absorbance (SUVA) were correlated to peak discharge, suggesting that the DOC exiting the watershed during snowmelt is highly aromatic (reactive). Our results suggest that the permafrost confines snowmelt and rainfall to shallow, near-surface flow paths. Increased contact time of the snowmelt with organic-rich material, lack of contact with mineral soil particles, and decreased biodegradation result in enhanced transport of DOC to the stream and increased export of DOC from the watershed. It is expected that with progressive melting of the permafrost, DOC export from the American Creek watershed will initially increase as new carbon from the melted permafrost becomes available. Over the long-term, however, it is possible that DOC export will decrease in response to two processes; 1) the new carbon pool will eventually be depleted due to increased microbial degradation, and 2) flow paths will be deeper with the absence of the permafrost table, moving through the soil mineral horizons to the stream. DOC in ground water along these deeper flow paths will likely react with the mineral horizon, effectively filtering out the DOC before it enters the stream.
DE: 1806 Chemistry of fresh water
DE: 1823 Frozen ground
DE: 1871 Surface water quality
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting