Fearon G. auteur aut IRD Herbette S. auteur aut IRD Veitch J. auteur aut IRD Cambon Gildas auteur aut IRD Lucas A. J. auteur aut IRD Lemarie F. auteur aut IRD Vichi M. auteur aut IRD text journalArticle eng text/pdf born digital access 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. specialized inertial oscillation land-sea breeze diurnal-inertial resonance coastal upwelling diapycnal mixing phytoplankton blooms ATLANTIQUE AFRIQUE DU SUD BENGUELA 032 036 020 125 9 e2020JC016208 [23 p.] 2020 2169-9275 https://www.documentation.ird.fr/hor/fdi:010079769 10.1029/2020jc016208 2169-9275 [F B010079769] https://www.documentation.ird.fr/hor/fdi:010079769 https://www.documentation.ird.fr/intranet/publi/2020/10/010079769.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2020-11-12 2025-02-24 fdi:010079769 fre