HR: 09:30h
AN: U41B-07    [Abstracts]
TI: Regional and Large-Scale Climate Influences on Tree-Ring Reconstructed Null Zone Position in San Francisco Bay
AU: * Stahle, D
EM: dstahle@uark.edu
AF: Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, United States
AU: Griffin, D
EM: rdgriff@uark.edu
AF: Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, United States
AU: Cleaveland, M
EM: mcleavel@uark.edu
AF: Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, United States
AU: Fye, F
EM: ffye@uark.edu
AF: Department of Geosciences, University of Arkansas, Fayetteville, AR 72701, United States
AU: Meko, D
EM: dmeko@ltrr.arizona.edu
AF: Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721, United States
AU: Cayan, D
EM: cayan@seaaira.ucsd.edu
AF: U.S. Geological Survey, Scripps Institution of Oceanography, La Jolla, CA 92093-0224, United States
AU: Dettinger, M
EM: mdettinger@ucsd.edu
AF: U.S. Geological Survey, Scripps Institution of Oceanography, La Jolla, CA 92093-0224, United States
AU: Redmond, K
EM: krwrcc@dri.edu
AF: Western Regional Climate Center, Desert Research Institute, Reno, NV 89512-1095, United States
AB: A new network of 36 moisture sensitive tree-ring chronologies has been developed in and near the drainage basins of the Sacramento and San Joaquin Rivers. The network is based entirely on blue oak (Quercus douglasii), which is a California endemic found from the lower forest border up into the mixed conifer zone in the Coast Ranges, Sierra Nevada, and Cascades. These blue oak tree-ring chronologies are highly correlated with winter-spring precipitation totals, Sacramento and San Joaquin streamflow, and with seasonal variations in salinity and null zone position in San Francisco Bay. Null zone is the non-tidal bottom water location where density-driven salinity and river-driven freshwater currents balance (zero flow). It is the area of highest turbidity, water residence time, sediment accumulation, and net primary productivity in the estuary. Null zone position is measured by the distance from the Golden Gate of the 2 per mil bottom water isohaline and is primarily controlled by discharge from the Sacramento and San Joaquin Rivers (and ultimately by winter-spring precipitation). The location of the null zone is an estuarine habitat indicator, a policy variable used for ecosystem management, and can have a major impact on biological resources in the San Francisco estuary. Precipitation-sensitive blue oak chronologies can be used to estimate null zone position based on the strong biogeophysical interaction among terrestrial, aquatic, and estuarine ecosystems, orchestrated by precipitation. The null zone reconstruction is 626-years long and provides a unique long term perspective on the interannual to decadal variability of this important estuarine habitat indicator. Consecutive two-year droughts (or longer) allow the null zone to shrink into the confined upper reaches of Suisun Bay, causing a dramatic reduction in phytoplankton production and favoring colonization of the estuary by marine biota. The reconstruction indicates an approximate 10 year recurrence interval between these consecutive two-year droughts and null zone maxima. Composite analyses of the Palmer drought index over North America indicate that the drought and wetness regimes associated with maxima and minima in reconstructed null zone position are largely restricted to the California sector. Composite analyses of the 20th century global sea surface temperature (SST) field indicate that wet years over central California with good oak growth, high flows, and a seaward position for the null zone (minima) are associated with warm El Nino conditions and a "Pineapple Express" SST pattern. The composite SST pattern is not as strong during dry years with poor growth, low flows, and a landward position of the null zone (maxima), but the composite warm SST anomaly in the eastern North Pacific during maxima would be consistent with a persistent ridge and drought over western North America.
DE: 1833 Hydroclimatology
DE: 1854 Precipitation (3354)
DE: 3344 Paleoclimatology (0473, 4900)
DE: 4235 Estuarine processes (0442)
SC: Union [U]
MN: 2007 Joint Assembly