Effects of Coastal Upwelling and Downwelling on Hydrographic Variability and Dissolved Oxygen in Mobile Bay

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.

Compounding impact of severe weather events fuels marine heatwave in the coastal ocean

“…The instrument suite has changed over time, but typically consists of bottom (~0.4 m above bottom, mab) and near-surface (~15.5 mab) CTD instruments, and 4-9 thermistors. Details of the mooring configurations and aspects of the processing can be found in various studies 33,34 . Importantly, the summer of 2018 featured an additional data stream from a CTD on a surface buoy (~100 m apart from site CP), providing data at~19.5 mab (i.e.,~0.5 m below the surface).…”

“…While surface temperature is the means though which tropical cyclones interact with the ocean, this study focuses on depth-average temperature as averaging over the expected mixing depth of a storm has been suggested or shown be to the most relevant property for storm intensification 35 – 37 , particularly over a shallow shelf 9 , 12 . The sensible and latent heat fluxes were calculated with the TOGA-COARE algorithms 35 similar to other studies in the region 34 . Conversion between relative humidity and dew point temperature was conducted following the standard algorithms ( https://bmcnoldy.rsmas.miami.edu/Humidity.html ) 38 – 40 .…”

Review of Dissolved Oxygen Detection Technology: From Laboratory Analysis to Online Intelligent Detection

“…ProOBOD series optical measuring instrument manufacted by YSI company is equipped with a high-performance pre-amplifier to ensure long-distance transmission without interference, and its digital dissolved oxygen sensor stores calibration data without recalibration. Aanderaa and Sea-Bird spend a lot of effort on compensation calibration, and their dissolved oxygen sensors are highly intelligent and have good detection results [199]. Therefore, experts often take the dissolved oxygen sensors of Aanderaa and Sea-Bird as the basic equipment for research on intelligent dissolved oxygen sensors [200].…”

Transport Processes in the Gulf of Mexico Along the River-Estuary-Shelf-Ocean Continuum: a Review of Research from the Gulf of Mexico Research Initiative

“…Exchange flows tend to be laterally sheared under weakly stratified (top-to-bottom density differences < 2 kg/m 3 ) or vertically mixed conditions, and vertically sheared otherwise (Valle-Levinson 2011;Huguenard et al 2015;Valle-Levinson et al 2015;Cui et al 2018). Deep ship channels were also shown to be a critical pathway by which offshore subsurface material could be rapidly transported into estuarine systems (Coogan et al 2019).…”