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Interannual and decadal variability of the primary productivity and oxygen Minimum Zone in the Peruvian Upwelling System

Abstract : The Peruvian upwelling system is one of the most productive regions of the world ocean and has a minimum oxygen zone (ZMO) in the sub-surface layers. This system is impacted by the El Niño (EN) and La Niña (LN) interannual climate events. We first study the impact of EN and LN events on primary productivity and dissolved oxygen, then the trends over the last decades. A coupled physics biogeochemical regional model, validated with observations, is used to study the hydrodynamic processes and biogeochemical cycles from 1958 to 2008. The model is able to realistically reproduce oceanic conditions during EN and LN phases, as well as trends observed in recent decades. During EN, chlorophyll decreases due to the deepening of the rich layers forced by the coastal waves and the limitation by the light in summer. The surface layer becomes more ventilated as the oxycline deepens. The source waters of the OMZ come from a more ventilated equatorial region. In recent decades, the productivity increase in summer and the progressive deoxygenation of subsurface waters are mainly due to equatorial variability, while local winds seem to play a minor role.
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Dante Espinoza Morriberón. Interannual and decadal variability of the primary productivity and oxygen Minimum Zone in the Peruvian Upwelling System. Oceanography. Sorbonne Université, 2018. English. ⟨NNT : 2018SORUS338⟩. ⟨tel-02864783⟩

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