HR: 0800h
AN: OS41B-0481    [Abstracts]
TI: Modeling bottom mixed layer variability on the mid-Oregon shelf during summer upwelling
AU: * Kurapov, A L
EM: kurapov@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 COAS Admin Bldg, Corvallis, OR 97331 United States
AU: Allen, J S
EM: jallen@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 COAS Admin Bldg, Corvallis, OR 97331 United States
AU: Egbert, G D
EM: egbert@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 COAS Admin Bldg, Corvallis, OR 97331 United States
AU: Miller, R N
EM: miller@coas.oregonstate.edu
AF: College of Oceanic and Atmospheric Sciences, Oregon State University, 104 COAS Admin Bldg, Corvallis, OR 97331 United States
AB: Results from a model of wind-driven circulation are analyzed to study spatial and temporal variability in the bottom mixed layer (BML) on the mid-Oregon shelf in summer 2001. The model assimilates acoustic Doppler profiler velocities from two cross-shore lines of moorings 90 km apart, to provide improved accuracy of near-bottom velocities and turbulence variables in the area between the mooring lines. Data assimilation provides a dynamically significant effect on the intensity and the time of occurrence of the mixing events. Model results suggest that the response of the BML thickness to upwelling and downwelling favorable winds differs qualitatively between an area of ``simple'' bathymetric slope at 45N and a wider shelf area east of Stonewall Bank (44.5N). At 45N, the BML grows in response to downwelling favorable conditions, in agreement with known theories. East of Stonewall Bank, however, the BML thickness is increased following upwelling events. In this area, the southward upwelling jet detaches from the coast and flows over a wider part of the Oregon shelf creating conditions for Ekman pumping near the bottom. Based on computations of bottom stress curl, the vertical pumping velocity in this area may reach 15 m/day following periods of intensified upwelling-favorable winds. A column of denser, near-bottom water upwelled over the Ekman flow convergence area is tilted as a result of vertical shear in horizontal velocities, causing unstable stratification and convective overturning. The bottom stress curl, used as an indicator of the intensity of the bottom Ekman pumping and BML growth east of Stonewall Bank, is difficult to obtain from measurements, but is readily available as an output from the numerical model.
DE: 4219 Continental shelf processes
DE: 4255 Numerical modeling
DE: 4263 Ocean prediction
DE: 4279 Upwelling and convergences
DE: 4568 Turbulence, diffusion, and mixing processes
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting