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Dryad

Data from: Interplay between wind-driven advection and mixing of salt and dissolved oxygen in a microtidal estuary

Data files

Feb 19, 2024 version files 3.09 MB

Abstract

Most work on how estuarine dynamics impact dissolved oxygen (DO) distributions has focused on tides as the primary mixing mechanism, but in shallow estuaries with large fetch or small tides, wind can be the primary mixing agent and also drives advection. To investigate how these processes interact and affect DO distributions, an observational study was conducted in the shallow, micro-tidal Neuse Estuary (NRE). Salinity, DO, and velocity profiles were measured at multiple positions along and across the estuary over a 6-month period. A one-dimensional model (General Ocean Turbulence Model) provided additional insight into the response of salinity and DO to wind.  Salinity and oxygen conservation equation terms were calculated from observations and simulations to investigate the roles of advection and mixing under different conditions. Cross-estuary wind drove lateral circulations and tilted the isohalines, reducing stratification; lateral advection and enhanced vertical mixing reduced vertical gradients and increased the bottom DO. Down-estuary wind tended to increase the exchange flow and increase stratification, but concurrently the wind-driven surface turbulent boundary layer deepened over time. The balance of these processes determined if the water column became fully mixed or remained stratified, and the depth of the pycnocline and oxycline. Up-estuary wind inhibited the exchange flow and ultimately the combination of advection and vertical mixing homogenized the water column. While these patterns generally held for purely across- or along-channel wind, the response was often more complex because the wind vector could have any orientation and wind speed and direction varied continuously with time.