Fronts and variability in the coastal ocean
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The coastal ocean is characterized by strong gradients in water properties, which influences circulation and ocean-atmosphere interactions. Fronts and variability in the coastal ocean are studied using a combination of satellite observations and numerical model simulations. Satellite sea surface temperature (SST) and wind observations are used to describe the seasonal evolution of temperature fronts and their relation to wind forcing in Eastern Boundary Current Systems (EBCS). Front activity is closely related to seasonal variability in wind forcing and to the presence of topographic perturbations such as capes. Investigation of the coupling between SST gradients and wind variables in the global coastal ocean reveals that regions with strong front activity are generally also characterized by strong ocean-atmosphere interaction. Mid-latitude regions, especially in EBCS, are characterized by enhanced ocean-atmosphere coupling during local summer. In several low-latitude regions, however, the coupling is stronger during winter. Although the coupling between SST gradients and wind stress divergence is stronger at seasonal scales, intraseasonal variability associated with mesoscale eddies is stronger for the coupling between SST gradients and wind stress curl. Coastal regions can also present strong salinity gradients, especially near river mouths. The circulation at a complex estuarine system off Georgia is investigated using a numerical model. The estuary includes three major sounds that are connected by a network of channels, creeks and intertidal areas. Spatial and temporal variability in residence time and connectivity between the sounds are influenced primarily by the Altamaha River discharge, by seasonally-varying winds, and by tidal forcing.