HR: 14:30h
AN: GC52A-04    [PDF]
TI: A Widespread Trend Towards Earlier Streamflow Timing Across North America Over the Past 5 Decades
AU: * Stewart, I T
EM: istewart@meteora.ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093 United States
AU: Cayan, D R
EM: dcayan@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093 United States
AU: Dettinger, M D
EM: dettinge@merced.ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093 United States
AB: This study examined the year-to-year variations in the timing of streamflow since the late 1940's for a network of gauges across North America from the United States and Canada. Within this network, a predominant fraction of streams exhibit a trend towards earlier occurrence of the major seasonal flows. Advances in seasonal flows ranged from one to four weeks earlier. This result is seen from inspection of monthly and seasonal fractional flow, the date of the center of mass for flow (CT), and for snowmelt-dominated streams, the start of snowmelt streamflow pulse. There is considerable spatial coherence of streamflow timing changes in regions including much of western North America, the Midwestern United States, and the Atlantic region. Both snowmelt and non-snowmelt dominated streams exhibited earlier streamflow timing, although non-snowmelt streams in the far western United States tended to display later timing. The earlier timing of snowmelt-derived streamflow in the western United States and western Canada was most strongly connected with warmer winter and spring temperatures. Surprisingly though, significant trends towards earlier timing of streamflow are not only observed throughout the West, but also in three eastern and southern regions of North America, where precipitation and streamflow are more evenly distributed throughout the water year. Correlations of streamflow timing with Pacific Decadal Oscillation (PDO) and the Southern Oscillation Index (SOI) indicate that a significant fraction of the variability is related to interannual and decadal climatic modes.
DE: 1630 Impact phenomena
DE: 1655 Water cycles (1836)
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
SC: Global Climate Change [GC]
MN: 2003 Fall Meeting