Coastal jets over canyons during transient winds: disentangling the dynamics and impacts in a Baltic Sea basin.

Wind-driven coastal upwelling and downwelling are salient features of the Baltic Sea circulation. A channel-like Western Gotland Basin, bounded by the Swedish east coast and Gotland, is a crucial region for the marine ecosystem and fisheries and water resources management (desalination plants on Gotland). Transient winds varying on a few-day time scale and complex bathymetry make the coastal dynamics highly complex and their impacts on the biogeochemistry of the area, temperature variability and the operation of the desalination plants are still not well understood. In this work, we combined MITgcm idealized simulations and reanalysis products. The MITgcm idealized model is initialized with November stratification (usual oxygen minimum perturbed by coastal dynamics) and´is forced by an alternation of short alongshore moderate wind events (2-4 days) in a channel. Our simulations show that localized variations in bottom bathymetry can excite coastally trapped waves, leading to asymmetries in the impacts of upwelling and downwelling jets on surface and bottom tracers in a larger region than the bathymetryic feature itself. Propagating waves can induce cross-isobath transport at locations and times not predicted by alongshore wind forcing alone, thereby adding further challenges to the forecasting of natural hazards on coastal infrastructures, such as desalination plants.