HR: 14:50h
AN: OS52F-04    [PDF]
TI: Seasonal and Tidal Patterns of Exchange at the Ocean-Estuary Interface: San Francisco Bay
AU: * Fram, J P
EM: jfram@uclink.berkeley.edu
AF: UC Berkeley, Environmental Engineering 631 Davis Hall, Berkeley, CA 94720 United States
AU: Martin, M
EM: maursm@uclink.berkeley.edu
AF: UC Berkeley, Environmental Engineering 631 Davis Hall, Berkeley, CA 94720 United States
AU: Stacey, M T
EM: mstacey@socrates.berkeley.edu
AF: UC Berkeley, Environmental Engineering 631 Davis Hall, Berkeley, CA 94720 United States
AU: Cuetara, J
EM: jcuetara@usgs.gov
AF: US Geological Survey, Placer Hall 6000 J Street, Sacramento, CA 95819
AU: Burau, J
EM: jburau@usgs.gov
AF: US Geological Survey, Placer Hall 6000 J Street, Sacramento, CA 95819
AB: Exchange between a subembayment and the coastal ocean is examined using direct observations of currents and scalar concentrations across the mouth of San Francisco Bay. Each experiment extends over two diurnal tidal cycles and is repeated during three `seasons': winter/spring runoff, summer upwelling, and fall relaxation, during both neap and spring tides. Within each study, transects across the channel are repeated approximately every 12 minutes for 25 hours; data presented here were collected during March, 2002 and November, 2002 and June, 2003. Instrumentation includes a boat-mounted ADCP and a tow-yoed SeaSciences Acrobat for collection of scalar data, including salinity, temperature, turbidity, and chlorophyll. A surface CT and a surface to bed vertical scalar profiler were also used. Empirical orthogonal function (EOF) analysis of the velocity and density data shows the spatial structures that persist over time. After the barotropic flow EOF, the next most significant flow EOFs represent tidal pumping, baroclinic circulation, and north-south exchange. For salinity, the order of EOF structure is barotropic advection, vertical stratification, north-south stratification, and then tidal pumping. Recurring features in the EOF time series across seasons show regular patterns of exchange, including subtle features such as a front on the north side of the channel during the beginning of ebb tide, phase shifts (in the vertical and horizontal) due to frictional effects and stratification, and strain induced periodic stratification. Analysis of the velocity and salinity fields using harmonics quantifies the salt flux and can be decomposed into individual flux mechanisms. The dispersive fluxes into the Bay are dominated by tidal pumping, with steady exchanges having vertical and horizontal structure providing the remainder of the flux. For all three seasons, the total dispersive influx is slightly larger than the advective salinity efflux, which is consistent with the expected net flux during each of the three experiments.
UR: http://www.ce.berkeley.edu/research/fluids
DE: 4235 Estuarine processes
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting