The effect of barotropic and baroclinic tides on coastal stratification and mixing

Suanda, SH, Feddersen F, Kumar N.  2017.  The effect of barotropic and baroclinic tides on coastal stratification and mixing. Journal of Geophysical Research-Oceans. 122:10156-10173.

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circulation, driven, inner continental-shelf, modeling-system, models, new-england shelf, ocean model, Oceanography, point conception, semidiurnal internal tide, southern california, turbulence


The effects of barotropic and baroclinic tides on subtidal stratification and vertical mixing are examined with high-resolution, three-dimensional numerical simulations of the Central Californian coastal upwelling region. A base simulation with realistic atmospheric and regional-scale boundary forcing but no tides (NT) is compared to two simulations with the addition of predominantly barotropic local tides ( LT) and with combined barotropic and remotely generated, baroclinic tides (WT) with approximate to 100 W m(-1) onshore baroclinic energy flux. During a 10 day period of coastal upwelling when the domain volume-averaged temperature is similar in all three simulations, LT has little difference in subtidal temperature and stratification compared to NT. In contrast, the addition of remote baroclinic tides (WT) reduces the subtidal continental shelf stratification up to 50% relative to NT. Idealized simulations to isolate barotropic and baroclinic effects demonstrate that within a parameter space of typical U.S. West Coast continental shelf slopes, barotropic tidal currents, incident energy flux, and subtidal stratification, the dissipating baroclinic tide destroys stratification an order of magnitude faster than barotropic tides. In WT, the modeled vertical temperature diffusivity at the top (base) of the bottom (surface) boundary layer is increased up to 20 times relative to NT. Therefore, the width of the inner-shelf ( region of surface and bottom boundary layer overlap) is increased approximately 4 times relative to NT. The change in stratification due to dissipating baroclinic tides is comparable to the magnitude of the observed seasonal cycle of stratification.