The Role of Time- and Spatially Varying Wind in Coastal Circulation Based on High-Resolution Oceanic and Atmospheric Simulations

Wind forcing plays a central role in driving oceanic circulation, including in small bays where local wind is strongly modulated in space and time by complex coastal orography. However, progress in understanding wind-driven circulation in such regions has been limited by the availability of wind data with sufficiently high-resolution to resolve these locally modulated wind features. Here, we address this limitation using high-resolution (100 m) ocean simulations forced by simulated wind fields at the same resolution and validated against observations to examine the effects of spatiotemporally varying winds on circulation in a small bay. Simulations forced by spatiotemporally varying winds showed improved agreement with the observed riverine water distribution compared to simulations forced by spatially uniform winds. Among the improvements, a key feature was enhanced upwelling in the interior of the bay, driven primarily by wind stress divergence rather than curl. Analysis across timescales reveals that vertical motion is dominated by divergence-driven oceanic adjustment at timescales shorter than the local inertial period, whereas curl-driven dynamics become increasingly important as timescales increase. These results indicate that under strong spatiotemporal wind variability, wind stress divergence can play a primary role in driving short-timescale circulation in small bays. Our findings emphasize the critical importance of understanding coastal circulation within an integrated land–air–sea framework, in which coastal orography influences spatiotemporal wind variability, which in turn affects oceanic circulation and highlights the need to account for wind divergence-driven processes on short timescales when modeling and understanding circulation and associated material transport.