Processes controlling the redox budget for the oxic/anoxic water column of the Black Sea

A one-dimensional isopycnal model has been constructed to simulate 16 major components of the Black Sea biogeochemical structure and to discuss processes controlling the redox budget for the oxic/anoxic water column of the Black Sea. The model includes parameterizations of physical exchange in the water column that takes account of vertical advection and diffusion and lateral exchange between the Black Sea and the Bosporus Plume. The model incorporates parameterizations for 25 biogeochemical processes, which we have found to be important to simulate the redox biogeochemical structure over a period of several decades. Parameterizations for biogeochemical processes follow the principles of formal chemical kinetics. Limiting functions are not applied. Neither physical nor biogeochemical processes are limited to depth or density layers of water, making the generated biogeochemical structure flexible. The redox budget and importance of individual processes for the budget of oxygen, sulfide, nitrate, ammonium, organic matter, manganese and iron are discussed in detail. In particular, we demonstrate that the biogeochemical structure of the oxic and suboxic layer strongly depends on export production and climate-induced variations in ventilation. The redox budget and the biogeochemical structure of the anoxic zone highly depend on the lateral exchange between the Black Sea and the Bosporus Plume, which appears to be the major reason for the existence of the suboxic zone.