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You are here: Home / Events / Seminars / seminaires-septembre-2017-aout-2018 / jeudi-19-octobre-h-maske

by SEMSOU last modified Oct 11, 2017 01:12 PM
When Oct 19, 2017
from 11:00 AM to 12:00 PM
Where Salle Coriolis
Attendees Helmut Maske, Professor, CICESE, Mexico
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Helmut Maske,

Professor, Département de Microbiologie Marine, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Mexico

 

 

Title : What makes the sub-oxic mesopelagic zones off Peru and Mexico?

 

Abstract :

Oxygen profiles in the ocean generally show a discontinuity between 100 and 1000m in the form of a minimum. In certain regions, Sub-oxic Mesopelagic Zones (SMZ) this minimum reaches anoxic conditions, for example off Peru or Mexico. Why/how are these SMZs forms? The governing process is the formation of organic particles (POM) in the surface layer that will sink and be oxidized in the mesopelagic layer. The rate of this process has to be sufficiently high to form and maintain the SMZ against the diapycnic diffusion isopycnic transport of oxygen.

Mexican and Peruvian SMZs show very different surface oceanographic conditions. The Peruvian SMZ lies in a region of strong coastal upwelling with high productivity that can maintain a high POM flux rate. Off Mexico the ocean is seemingly oligotrophic, highly stratified and the question is where the POM flux originates. I suggest that the Mexican SMZ is ‘cryptically’ productive made possible by a large regional uplift of the pycnocline. This uplift is providing the necessary inorganic nutrients to the euphotic zone to stimulate primary productivity and the POM flux.

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