HR: 0800h
AN: U41A-0812    [Abstracts]
TI: Exploring the effects of precipitation changes on the variability of pan-arctic river discharge
AU: * Adam, J C
EM: jadam@u.washington.edu
AF: Department of Civil and Environmental Engineering, University of Washington, BOX 352700, Seattle, WA 98195-2700 United States
AU: Su, F
EM: fgsu@hydro.washington.edu
AF: Department of Civil and Environmental Engineering, University of Washington, BOX 352700, Seattle, WA 98195-2700 United States
AU: Lettenmaier, D P
EM: dennisl@u.washington.edu
AF: Department of Civil and Environmental Engineering, University of Washington, BOX 352700, Seattle, WA 98195-2700 United States
AB: River runoff to the Arctic Ocean has been shown to be increasing, primarily during the winter and spring and from the major Eurasian rivers. Recent studies suggest that the increase is likely due to increased northward transport of moisture (and associated increased precipitation), but other studies show inconsistencies in long-term runoff and precipitation trends. This suggests uncertainty in the observational datasets. Through a combination of exploratory data analysis and land surface modeling, we estimate the uncertainty inherent in the trends derived from gridded precipitation datasets and comment on the likelihood that runoff changes are due to long-term changes in precipitation. In our exploratory data analysis, we compare the seasonal and annual trends of four observation-based half-degree gridded monthly precipitation products: University of Delaware (UDel), Climatic Research Unit (CRU), PREC/L, and GPCC's VASClim0; along with two reanalysis products: NCEP/NCAR and ERA40. Included in the comparison are two variations of the UDel dataset created by applying an adjustment for spurious trends using high-quality station information to control for decadal scale variability. The precipitation trend characteristics are checked for consistency against R-ArcticNet v. 3.0's observed stream flow data and a published data set for large rivers from which the effects of dams have been removed. We also examine the temporal correlations of basin-mean precipitation and runoff anomalies at lags of zero to six months. Using the trend-adjusted UDel precipitation and CRU temperature data as forcing, we run the Variable Infiltration Capacity (VIC) macroscale hydrology model over the pan-arctic land domain for the period of 1930-2000. Trends in simulated stream flow are checked for consistency against observed and "naturalized" stream flow. Furthermore, the sensitivity of the simulated stream flow to the trend of the precipitation and temperature inputs is explored. While precipitation changes can explain changes in observed runoff in some cases, major discrepancies exist. This suggests that there are other contributing factors (e.g. land cover changes, permafrost degradation, other anthropogenic effects, etc).
DE: 0744 Rivers (0483, 1856)
DE: 0762 Mass balance (1218, 1223)
DE: 1621 Cryospheric change (0776)
DE: 1847 Modeling
DE: 1854 Precipitation (3354)
SC: Union [U]
MN: Fall Meeting 2005