Coastal winds dynamics in the Peruvian upwelling system under warming conditions : impact of El Niño and regional climate change

Abstract : The Peruvian upwelling system is one of the most productive coastal marine systems of the world ocean. As in other upwelling systems, alongshore surface wind is the main driver of the coastal upwelling. This thesis aims to study the coastal wind variability and the processes responsible for it during the ocean surface layer warming conditions, at different time scales: (1) interannual time scales, corresponding to El Niño events and (2) multi decadal time scales resulting from regional climate change. A suite of regional atmospheric model embedded domains is used to simulate the surface winds. In the first part of the thesis, the counter-intuitive wind increase observed off Peru during the 1997-1998 El Niño is studied. Sensitivity experiments show that the inhomogenous alongshore surface warming, larger in the north, drives an enhanced alongshore pressure gradient that accelerates the alongshore wind. In the second part of the thesis, the evolution of coastal wind changes is investigated under the “worst case” RCP8.5 climate change scenario. Mainly driven by the alongshore pressure gradient, summer winds decrease whereas winter winds increase, thus slightly reinforcing the seasonal cycle.
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Adolfo Chamorro Gómez. Coastal winds dynamics in the Peruvian upwelling system under warming conditions : impact of El Niño and regional climate change. Ocean, Atmosphere. Sorbonne Université, 2018. English. ⟨NNT : 2018SORUS066⟩. ⟨tel-02163945⟩

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