Together with the RECEIVER unit, we want to determine how the interactions and feedbacks between the marine biogeochemical cycles and the shelf-sea and open ocean circulation determine the fluxes of carbon and nutrients, as well as their budgets. To this end, a regional modeling system was newly designed (see Figure 1). The MIT general circulation model (MITgcm), which simulates the physical ocean circulation, was set up for the Northwest African upwelling system.
Currently we are working on implementing the different remaining modules that can be seen in Figure 1. The biogeochemistry module (green in Fig. 1) is a Nutrient-Phytoplankton-Zooplankton-Detritus model. Phytoplankton and detritus form together the pool for biogenic particle aggregation. The particle aggregation/disaggregation modeling (blue in Fig. 1) follows the approach of Kriest and Evans (1999) and Barkmann et al. (2010). Biogenic particles collide among each other and with lithogenic particles and form aggregates that sink to the ocean floor with a prognostic sinking velocity. The particles are represented by a continuous size spectrum, which is assumed to follow a certain power law, making it possible to model the entire range of particle sizes by only two prognostic variables. As a last step we plan to incorporate an early diagenesis model of pelagic sediments (MEDUSA, Munhoven 2007, brown in Fig. 1), which models the exchange of organic material and carbonates between the sediments and the ocean above.
The regional modeling system will be applied first to the Northwest African upwelling system, which is characterized by high productivity and high sedimentation rates, influenced by changes in the large-scale atmospheric and ocean circulation and atmospheric dust deposition.