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by Webmaster Legos last modified Sep 08, 2014 09:56 AM

Nitrogen transfers within an Oxygen Minimum Zone:

the Namibian upwelling (South-East Atlantic Ocean)


DYNBIO team: Isabelle Dadou (UPS), Véronique Garçon (CNRS), Elodie Gutknecht (PhD, ATER), Briac Le Vu (MEECE Postdoc, IRD)

Collaboration within LEGOS: ECOLA: Patrick Marchesiello, Gildas Cambon (IRD)

Collaboration with other laboratories: LPO (Brest, France), Leibniz Center for Tropical Marine Ecology and Max Plank Institute for Marine Microbiology (Bremen, Germany), Forschungsbereich Marine Biogeochemie, Helmholtz-Zentrum für Ozeanforschung (Kiel, Germany),

Project funded by CNES (TOSCA/OST-ST), Région Midi-Pyrénées, UPS.

Main results:

The performance of the physical/biogeochemical model (ROMS/BioEBUS) over the Namibian upwelling, after a sensitivity analysis on biogeochemical parameter values and N2O parameterizations, was evaluated using satellite and in situ data, especially the first N2O measurements offshore Namibia for a climatological simulation (Fig.1).


The simulated minimum oxygen concentrations are driven by the poleward meridional advection of oxygen-depleted waters offshore of a 300m isobath and by the biogeochemical activity inshore of this isobath, highlighting a spatial shift of dominant processes maintaining the minimum oxygen concentrations off Namibia (Fig.2).

Anammox contributes to about 20% of total N loss, an estimate lower than currently assumed (up to 50 %) for the global ocean. (Gutknecht et al., 2013a)



Gutknecht, E., 2011. « Interactions côte-large dans le système de l’upwelling du Benguela par modélisation couplée physique/biogéochimique », PhD Thesis, Paul Sabatier University, 259 pp.

Gutknecht, E., Dadou, I., Le Vu, B., Cambon, G., Sudre, J., Garçon, V., Machu, E., Rixen, T., Kock, A., Flohr, A., Paulmier, A., and Lavik, G., 2013a: Coupled physical/biogeochemical modeling including O2-dependent processes in Eastern Boundary Upwelling Systems: application in the Benguela, Biogeosciences, 10, 3559–3591, 2013, doi:10.5194/bg-10-3559-2013.

Gutknecht, E., Dadou, I., Marchesiello, P., Cambon, G., Le Vu, B., Sudre, J., Garçon, V., Machu, E., Rixen, T., Kock, A., Flohr, A., Paulmier, A., and Lavik, G., 2013:Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system, Biogeosciences, 10, 4117–4135, 2013, doi:10.5194/bg-10-4117-2013.

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