%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Fearon, G.
%A Herbette, S.
%A Veitch, J.
%A Cambon, Gildas
%A Lucas, A. J.
%A Lemarie, F.
%A Vichi, M.
%T Enhanced vertical mixing in coastal upwelling systems driven by diurnal-inertial resonance : numerical experiments
%D 2020
%L fdi:010079769
%G ENG
%J Journal of Geophysical Research : Oceans
%@ 2169-9275
%K inertial oscillation ; land-sea breeze ; diurnal-inertial resonance ; coastal upwelling ; diapycnal mixing ; phytoplankton blooms
%K ATLANTIQUE ; AFRIQUE DU SUD ; BENGUELA
%K SAINT HELENA BAIE
%M ISI:000576619900026
%N 9
%P e2020JC016208 [23 ]
%R 10.1029/2020jc016208
%U https://www.documentation.ird.fr/hor/fdi:010079769
%> https://www.documentation.ird.fr/intranet/publi/2020/10/010079769.pdf
%V 125
%W Horizon (IRD)
%X 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