Effects of Coastal Upwelling and Downwelling on Hydrographic Variability and Dissolved Oxygen in Mobile Bay Journal of Geophysical Research: Oceans

Abstract Upwellling and downwelling events are important coastal processes that strongly influence shelf ecosystem dynamics. Though changes on the shelf have been well studied, the impact of these events on estuarine systems has received less focus. In summer 2016 a downwelling and upwelling event were observed near the mouth of Mobile Bay. The impact of these events were examined throughout the bay with high spatial resolution observations. Five boat surveys were conducted to capture the spatial response of offshore forcing and its changes in the estuary. In addition to the surveys, 16 conductivity, temperature, and depth (CTD) sensors were deployed and measured temporal changes. A 7 ° C temperature change was observed in the channel as a result of the offshore changes. In the shipping channel and offshore, advection was a major source of changes in heat content and often exceeded the surface heat flux. Advection of low dissolved oxygen water into the estuary was also observed in the shipping channel and at the Dauphin Island station nearest to the estuary mouth. The extent of these changes highlights the importance of estuary-shelf connectivity in river-dominated systems where offshore forcing can drive large changes in estuaries during low flow summer conditions. Grant no. NA17NOS4510101