The roles of wind stress and wind stress curl in forcing the ocean dynamics in a coastal bay

One of the outstanding problems to be resolved is the roles of along-shore wind stress and the wind stress curl in generating coastal upwelling. Moreover, temporal and spatial scales relevant to the air-sea interaction are not understood well. Three-month long, 1 km horizontal resolution simulations with Mesoscale Model 5 (MM5) and field program data conducted over the California and Oregon coastal waters were used to investigate the effects of the along-shore wind stress and wind stress curl on the ocean dynamics in the Bodega Bay region, California. The data from five buoys arranged in a diamond shape with sides of about 30 km revealed the complex structure of the wind stress and the wind stress curl relevant to the ocean dynamics and marine biological cycle in Bodega Bay. One of the reasons for this temporally variable inhomogeneous flow field, which induces significant wind stress curl, is that Bodega Bay lies at the downwind edge of the temporally and spatially variable expansion fan caused by the Point Arena topography. The wind stress curl obtained from both the buoy data and the model results correlated well with the changes in the sea surface temperature on short time scales of a day or less. A comparison of the upwelling velocities obtained from measurements along the shelf and the simulated wind stress curl showed pronounced agreement. The results indicate that the ocean forcing of the wind stress curl could be of similar or sometimes of even higher importance than the forcing of the along-shore wind stress. Some of the preliminary ocean simulations using the forcing from the atmospheric model show that the evolution of the upwelling in the bay could be significantly related to wind structure and consequent ocean response at distant areas along the coast.