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The General Ocean Turbulence Model (GOTM) is a one-dimensional water column model, including a set of state-of-the-art turbulence closure models, and has widely been used in various applications in the ocean modeling community. Here, we extend GOTM to include a set of newly developed ocean surface vertical mixing parameterizations of Langmuir turbulence via coupling with the Community Vertical Mixing Project (CVMix). A Stokes drift module is also implemented in GOTM to provide the necessary ocean surface waves information to the Langmuir turbulence parameterizations, as well as to facilitate future development and evaluation of new Langmuir turbulence parameterizations. In addition, a streamlined workflow with Python and Jupyter notebooks is also described, enabled by the newly developed and more flexible configuration capability of GOTM. The newly implemented Langmuir turbulence parameterizations are evaluated against theoretical scalings and available observations in four test cases, including an idealized wind-driven entrainment case and three realistic cases at Ocean Station Papa, the northern North Sea, and the central Baltic Sea, and compared with the existing general length scale scheme in GOTM. The results are consistent with previous studies. This development extends the capability of GOTM towards including the effects of ocean surface waves and provides useful toolsets for the ocean modeling community to further study the effects of Langmuir turbulence in a broader scope. [ABSTRACT FROM AUTHOR]

Cross-channel transect measurements of microstructure and velocity in a well-mixed and curved tidal inlet in the German Wadden Sea show the occurrence of significant late flood stratification. This stratification is found to be a result of lateral straining. This study observes a strong single-cell lateral circulation, which is strongly pronounced at late flood and absent during most of ebb. This tidal asymmetry is caused by a systematic interplay between centrifugal forcing and the lateral baroclinic pressure gradient. During flood a positive feedback between the terms generates strong lateral circulation, whereas during ebb a negative feedback leads to a suppression of the cross-channel exchange. A theoretical framework based on vorticity is developed, which allows lateral and longitudinal circulation to be studied in a consistent way. With this framework it is possible to show that the tidal asymmetry of the lateral flow is a major driver of residual longitudinal estuarine circulation, here identified with the tidally averaged across-channel vorticity component. [ABSTRACT FROM AUTHOR]

Large-scale geophysical flows often exhibit layers with negligible vertical shear and infinite gradient Richardson number Ri. It is well known that these layers may be regions of active mixing, even in the absence of local shear production of turbulence because, among other processes, turbulence may be supplied by vertical turbulent transport from neighboring regions. This observation is contrasted by the behavior of most turbulence parameterizations used in ocean climate modeling, predicting the collapse of mixing of mass and matter if the Richardson number exceeds a critical threshold. Here, the performance of a simple model without critical Richardson number is evaluated, taking into account the diffusion of turbulence into layers without shear production and therefore avoiding the suppression of mixing at large values of Ri. The model is based on the framework of second-moment turbulence closures, focusing on the consistent modeling of the turbulent length scale for strongly stratified turbulence. Results are compared to eddy-resolving simulations of stratified shear flows that have recently become available. The model is simple enough for inclusion in ocean climate models. [ABSTRACT FROM AUTHOR]

Abstract: In the transition area between the North Sea and the Baltic Sea entrainment processes dominate the vertical mixing in the inflowing saline bottom water. The hot spots of these processes are located at the Darss Sill and the Bornholm Channel in the western Baltic Sea. In the central Baltic Sea the horizontal advection of saline water in deep layers below the permanent halocline dominate the temporal changes and associated transports. This is accompanied by the turbulent vertical transport through the halocline into the surface layers. The related vertical salt transport into the entire surface mixed layer estimated by various methods is slightly above 30kg/(m2 a). During stagnation periods, the residence time of the deep water in the Eastern Gotland Basin increases roughly by a factor of five. Vertical mixing through the halocline is drastically reduced when inflows are lacking, the potential processes of diapycnal mixing are discussed to the present knowledge. The turbulent motion resulting from breaking internal waves is capable of turbulent transports through the halocline corresponding to the estimates of the salt transport into the surface mixed layer. The actual knowledge about boundary mixing due to internal waves in the Baltic Sea is poor. Mesoscale eddies may contribute to the vertical mixing, but it is not known whether they really do and which of the possible direct and indirect mixing mechanisms is most effective. Near-bottom currents induced by inflow events likely enhance vertical mixing. Coastal upwelling certainly contributes to the vertical transport, but the depth of its origin and the volume transport are hard to determine for large-scale quantifications. The short spatiotemporal scale of turbulent transports through the halocline resulting in a weakening of the halocline during summer together with the mixing of the entire surface layer down to the halocline in winter form a consistent description of the vertical salt transport. It is hypothesised that the longer residence time of the deep water during stagnation periods results from the lack of energy imported by the inflows and directly or indirectly feeding the diapycnal mixing processes. The vertical transport of nutrients such as the phosphate is quantitatively not sufficiently understood and needs further interdisciplinary research activities. [Copyright &y& Elsevier]