Bopp¹, L., O. Aumont² and M. Gehlen¹

¹IPSL/LSCE, Orme des Merisiers, CE Saclay, F-91191 Gif sur Yvette, Tel: +33 1 69 08 32 74, Fax: +33 1 69 08 77 16, E-mail: bopp@lsce.saclay.cea.fr, and ²IPSL/LODYC, U.P.M.C., Place Jussieu, F-75005 Paris

Mechanistic representation of particles dynamic in a biogeochemical model of the global ocean

The flux of organic matter from surface waters to the deep ocean has a direct influence on the partitioning of CO₂ between the ocean and atmosphere. In all commonly-used biogeochemical global models of the ocean, this flux of organic matter sinking below the photic zone is described as a function of the export of organic carbon from the base of the photic zone, scaled to depth with an exponential (Martin et al. 1987) or inverse (Suess 1980) function. Several studies have shown the limits of such parametrizations (e.g., Lutz et al. 2002). Following Kriest and Evans (2001) approach, we propose to explicitly represent the sinking of particles below the photic zone and to incorporate a mechanistic representation of aggregation/disaggregation of particles in a global Oceanic Biogeochemical Model (OBM). This approach enables us to explicitly model the change with time and space in the distibution of aggregate sizes and sinking speeds. Results of climatological simulations using this mechanistic representation will be presented, along with a comparison to previously-used approaches.

Kriest and Evans, Proc. Indian Acad. Sci. 109, 453-469, 2000.

Lutz et al., Global. Biogeochem. Cycles, 16, 2002.

Martin et al., Deep Sea Res., 34, 267-285, 1987.

Suess, Nature, 288, 260-263, 1980.