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Abstract The dynamics of ocean‐estuary exchange depend on a variety of local and remote ocean forcing mechanisms where local mechanisms include those directly forcing the estuary such as tides, river discharge, and local wind stress; remote forcing includes forcing from the ocean such as coastal wind stress and coastal stratification variability. We use a numerical model to investigate the limits of oceanic influence, such as wind‐driven upwelling, on the Salish Sea exchange flow and salt transport. We find that along‐shelf winds substantially modulate flow throughout the Strait of Juan de Fuca until flow reaches sill‐influenced constrictions. At these constrictions the exchange flow variability becomes sensitive to local tidal and river forcing. The salt exchange variability is tidally dominated at Admiralty Inlet and upwelling has little impact on seasonal salt exchange variability. While within Haro Strait, the salt exchange variability is driven by a mix of coastal upwelling and local forcing including river discharge. There, the transition from oceanic to local control of salt exchange occurs over a longer distance and is primarily identifiable in the increasing variability of bulk outflowing salinity values. The differences between the two locations highlight how ocean variability interacts with both tidal pumping and gravitational circulation. We also distinguish between transient ocean forcing which can modify fjord properties near the mouth of the strait and seasonal ocean forcing which primarily affects along‐strait pressure gradients. The results have implications for understanding the transport variability of biogeochemical variables that are influenced by both along‐shelf winds and local sources. 

Abstract Westward-propagating Caribbean Current eddies modify the volume-integrated potential vorticity (PV) balance in the western Caribbean Sea, influencing the circulation of the Panamá–Colombia Gyre (PCG) and coastal currents hundreds of kilometers to the south of the eddies’ mean trajectory. Using 22 years of output from the Hybrid Coordinate Ocean Model, we apply a volume-integrated eddy phase-averaged 1.5-layer PV balance, showing that PV fluxes into the PCG region are balanced by frictional PV dissipation represented by linear drag along the coastline. Coastal currents in the PCG region vary by a factor of 2 in phase with the passage of a Caribbean Current eddy over the 116-day average eddy period. Flow separation at the Isthmus of Panamá results in a vortex shed from the Darien Gulf, which slows the coastal currents in the gyre region from their maximum during eddy events. An annual ensemble average PV balance in the gyre region shows that the mean PV influx to this region is higher from August to October. Correspondingly, the range of coastal currents in the gyre region over an eddy event is modestly influenced by the PV influx magnitude. Eddy-influenced reversals in the coastal current can occur between November and July at Bocas del Toro and year-round at Colón. Such coastal current reversals are important for the alongshore transport of larvae, freshwater, and chemical tracers.