Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Journal of Geophysical Research : Oceans e2020JC016208 [23 p.] inertial oscillation land-sea breeze diurnal-inertial resonance coastal upwelling diapycnal mixing phytoplankton blooms ATLANTIQUE AFRIQUE DU SUD BENGUELA SAINT HELENA BAIE 2020 fdi:010079769 ENG Journal of Geophysical Research : Oceans 2169-9275 ISI:000576619900026 9 10.1029/2020jc016208 https://www.documentation.ird.fr/hor/fdi:010079769 https://www.documentation.ird.fr/intranet/publi/2020/10/010079769.pdf 125 Horizon (IRD) The land-sea breeze is resonant with the inertial response of the ocean at the critical latitude of 30 degrees N/S. 1-D vertical numerical experiments were undertaken to study the key drivers of enhanced diapycnal mixing in coastal upwelling systems driven by diurnal-inertial resonance near the critical latitude. The effect of the land boundary was implicitly included in the model through the "Craig approximation" for first-order cross-shore surface elevation gradient response. The model indicates that for shallow water depths (<similar to 100 m), bottom shear stresses must be accounted for in the formulation of the "Craig approximation," as they serve to enhance the cross-shore surface elevation gradient response, while reducing shear and mixing at the thermocline. The model was able to predict the observed temperature and current features during an upwelling/mixing event in 60 m water depth in St Helena Bay (similar to 32.5 degrees S, southern Benguela), indicating that the locally forced response to the land-sea breeze is a key driver of diapycnal mixing over the event. Alignment of the subinertial Ekman transport with the surface inertial oscillation produces shear spikes at the diurnal-inertial frequency; however their impact on mixing is secondary when compared with the diurnal-inertial resonance phenomenon. The amplitude of the diurnal anticyclonic rotary component of the wind stress represents a good diagnostic for the prediction of diapycnal mixing due to diurnal-inertial resonance. The local enhancement of this quantity over St Helena Bay provides strong evidence for the importance of the land-sea breeze in contributing to primary production in this region through nutrient enrichment of the surface layer. 032 ; 036 ; 020 UR254 Afrique du Sud