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Modulation of frontogenetic plankton production along a meandering jet by zonal wind forcing: An application to the A lboran S ea
Author(s) -
Oguz Temel,
Mourre Baptiste,
Tintoré Joaquin
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2017jc012866
Subject(s) - geology , ocean gyre , jet (fluid) , oceanography , anticyclone , mesoscale meteorology , mediterranean sea , climatology , upwelling , advection , atmospheric sciences , environmental science , mediterranean climate , subtropics , physics , geography , archaeology , fishery , biology , thermodynamics
Abstract We present a coupled physical‐biological modeling study to elucidate the changes in ageostrophic frontal dynamics and the frontogenetic plankton production characteristics of a meandering jet under the impacts of successive westerly/easterly wind events combined with seasonal variations in the upstream transport and buoyancy flux characteristics of the jet, using a case study for the Alboran Sea (Western Mediterranean). Their nonlinear coupling is shown to result in different forms of physical and biological characteristics of the background jet structure that follows a meandering path around two anticyclonic gyres in the western and eastern basins and a cyclonic eddy in between. The westerly, downfront wind events broaden the jet, and result in stronger cross‐frontal density contrast and intensify ageostrophic cross‐frontal secondary circulation. Thus, they improve the frontogenetic plankton production with respect to the no‐wind case. They also support higher production along the northern coast in response to wind‐induced coastal upwelling and spreading of resulting nutrient‐rich, productive water by mesoscale stirring. These features weaken gradually as the jet transport reduces. In contrast, stronger and longer‐lasting easterlies during the reduced jet transport phase weaken the currents and frontal density structure, change the circular Western Alboran Gyre to an elongated form, and shift the main axis of the jet towards the southern basin. Then, frontogenesis fails to contribute to phytoplankton production that becomes limited to the eddy pumping within cyclones. Apart from the frontogenetic production, eddy pumping, mesoscale stirring, and diapycnal mixing of nutrients support intermittent and localized phytoplankton patches over the basin.