Horizontal and Vertical Exchanges of Nitrogen the Mediterranean Sea

The nitrogen budget of the Mediterranean Sea, discussed in this work, is based on estimating dynamically the fluxes that control the exchanges among the subbasins. The vertical dynamics, governed by advection-diffusion processes and convective adjustments, create entrainment and subduction of the passive tracers such as the biological state variables across the euphotic zone. Moreover inorganic nitrogen entrainment in the euphotic zone can be related with the new production assessment and the seasonal variability at the Gibraltar Strait can influence directly or indirectly the productivity of the whole basin. The nitrogen fluxes are determined both in terms of total and inorganic nitrogen using a trophodynamic numerical model. This model is tightly coupled with the MOM set up for the Mediterranean Sea by Pinardi et al. (1993). The effects on biology of the entrainment of nutrients from the euphotic zone and the balancing of exporting dead matter to the aphotic zone are shown. The horizontal exchanges among the main basins turn out to be advection driven and an attempt to estimate the barotropic and baroclinic flux contributions is presented.