Some considerations about non-hydrostatic vs. hydrostatic simulation of short-period internal waves. A case study: The Strait of Gibraltar

Understanding tidal mixing at the Strait of Gibraltar: A high-resolution model approach

“…As a further step in understanding tidal mixing at the SoG, this study would gain from comparison with a very-highresolution non-hydrostatic counterpart, allowing to investigate the role played by high-order internal wave baroclinic modes, which are a key component of the energy cascade over abrupt topography (Lahaye et al, 2020). Although the mechanisms highlighted in this study should remain consistent, fine-scale and non-hydrostatic features, such as short internal solitary waves formed along the trail of the eastward internal bore released at the CS, should affect the intensity and location of diapycnal mixing (Hilt et al, 2020;Álvarez et al, 2019;Sannino et al, 2014). Such study could also assess the consistency of the highlighted recirculation cells to the relaxation of the hydrostatic assumption.…”

“…More recently, high-resolution simulations using realistic physical forcing have emerged (Sannino et al, 2004(Sannino et al, , 2007Sanchez-Garrido et al, 2011;García Lafuente et al, 2013;Sannino et al, 2014;Sanchez-Roman et al, 2018;Álvarez et al, 2019), allowing ocean modelers to reproduce and analyze in detail the main characteristics of the exchange flow through the SoG. While the eastward barotropic tide deepens and thick-ens the interface layer separating the Atlantic inflow from the Mediterranean outflow, the westward barotropic tide uplifts and shoals it, powering a periodic oscillation of the stratification and driving entrainment between both layers (Sannino et al, 2007;García Lafuente et al, 2013).…”

“…To this end, we analyze the processes driving turbulent mixing in ocean simulations of the Mediterranean Sea, including or not an explicit tide. Among the currently available numerical tools, we use a non-hydrostatic kilometric model resolution, which allows a faithful 3D representation of the exchange flow through the SoG and the largest internal waves at work (Hilt et al, 2020;Álvarez et al, 2019;Sannino et al, 2014). We consider that it provides an adequate framework to study the main mechanisms driving diapycnal mixing within the strait.…”

Effect of Internal Waves on the Hydrodynamics of a Mediterranean Sea Strait

“…Internal waves are inherently non-hydrostatic, but they are frequently resolved quite well in 3D hydrostatic coastal circulation models. The effect of the hydrostatic model assumption on the simulation of internal waves has been thoroughly studied by many research works [58][59][60][61][62], where characteristic model-observation discrepancies-arising from the hydrostatic approximation-have been discussed in detail. However, despite this assumption, the model simulates the baroclinic circulation in the strait, allowing the representation of internal waves and simulating the temporal variations in water temperature [50].…”