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Jeudi 13 Septembre - Oxygen Minimum Zones: mean state and decadal variability

Par SEMSOU Dernière modification 03/09/2018 15:32
Quand ? Le 13/09/2018,
de 10:00 à 11:00
Où ? salle Coriolis
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Olaf Duteil 

GEOMAR - Helmholtz Centre for Ocean Research, Kiel, Germany


Title: Oxygen Minimum Zones : mean state and decadal variability


Abstract: The processes controlling the mean state and the temporal variability of oxygen concentration in the interior ocean are poorly understood, in particular in the suboxic regions of the eastern tropical Pacific Ocean where oxygen concentrations are among the lowest worldwide. It is still not clear whether (or to which point) the current oxygen decline is due to anthropogenic changes or related with natural variability. In this talk, I will present results based on different experiments performed using a coupled biogeochemical-circulation model. After quantifying the processes (advection / diffusion / respiration) controlling the mean extension of the Oxygen Minimum Zones, we assessed the impact of the positive and negative phases of the Pacific Decadal Oscillation.We show that during a “typical” PDO positive phase the volume of the suboxic regions expands by 7 % in 50 years due to a slow-down of the large scale circulation related with the decrease of the intensity of the trade winds. Our results suggest that the prevailing PDO positive conditions since 1975 may explain a significant part of the current deoxygenation occurring in the eastern Pacific Ocean. Representing the oxygen cycle in ocean models is however a complicated task due to the interplay of a large range of mechanisms. I will discuss some limitations of the current modelling strategies.


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