HR: 16:15h
AN: H24B-02 INVITED     [Abstracts]
TI: Earlier snowmelt streamflow in western North America--a response to Pacific decadal variability or climate change?
AU: * Cayan, D R
EM: dcayan@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0224 United States
AU: * Cayan, D R
EM: dcayan@ucsd.edu
AF: US Geological Survey, 9500 Gilman Drive, La Jolla, CA 92093-0224 United States
AU: Stewart, I T
EM: istewart@meteora.ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92093-0224 United States
AU: Dettinger, M D
EM: mddettin@usgs.gov
AF: US Geological Survey, 9500 Gilman Drive, La Jolla, CA 92093-0224 United States
AB: Widespread trends toward earlier onsets of spring snowmelt and streamflow have occurred during the last five decades in snowmelt driven watersheds across western North America. Advances in spring timing of a few days to over three weeks are observed from a network of U.S. and Canadian stream gages. Such changes, if they continue, could pose an enormous challenge to water managers in providing a reliable water supply to the region. These changes are clearly a response to warmer winter and particularly warmer spring temperatures over the region, but a deeper question concerns the origin of the warming--is it simply a reflection of decadal climate fluctuations over the Pacific/North America sector or is it a reaction to broader scale climate warming? Evidence is presented suggesting that only part of the warming and only part of the streamflow changes can be attributed to fluctuations in the Pacific Decadal Oscillation (PDO). An equal or greater fraction of the variance appears to correspond with changes in global temperature over the period. Notably, the advances in streamflow timing occured during both cool (1948-1976) and warm (1977-1998) phases of the PDO. Further, although the PDO apparently reverted to its cool phase in 1999, spring temperatures in the West was anomalously warm and spring snowmelt-driven streamflow timing remained quite early during the last 6 years.
DE: 1655 Water cycles (1836)
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
DE: 1863 Snow and ice (1827)
DE: 1610 Atmosphere (0315, 0325)
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting