[1] A systematic quantitative assessment of the marine silicon cycle is presented, based on a prognostic coupled water column-sediment global biogeochemical ocean general circulation model (HAMOCC). The resulting tracer distributions are compared with a comprehensive marine Si database of measurements. The model parameters which govern the Si cycle within the model world are optimized through a linear response model. The functional relationships between the Si cycle parameters and the Si tracer distributions are derived from a series of sensitivity experiments addressing opal export production, particle flux through the water column, porewater chemistry, and external biogeochemical forcing. The most important parameters for a further quantitative improvement of the simulation are depth-dependent opal dissolution kinetics, a productivity-dependent opal settling velocity, a general change in maximum Si uptake velocity V max opal , and the clay as well as the Si input from continental weathering. The modeled Si budget shows a larger global export production, larger opal deposition rates onto the sediment surface and higher diffusive transports of porewater silicic acid into the open water column as estimated by Tréguer et al. [1995].

Abstract.A linear inverse mixing model is applied to hydrographic, nutrient, and carbon data collected during

The distribution of partial pressure of carbon dioxide and the concentrations of nitrous oxide and methane were investigated in a cold water filament near the coastal upwelling region off Oman at the beginning of the southwest monsoon in 1997. The results suggest that such filaments are regions of intense biogeochemical activity which may affect the marine cycling of climatically relevant trace gases.http://link.springer. de/link/service/journals/00114/bibs/9086010/90860489.htm

Abstract. An attempt is made to quantify the biological carbon pump in Arabian Sea subsurface waters by estimating the total concentrations of remineralized dissolved inorganic carbon (DlCrem) and its water column inventory. The influence of different sets of -AO2/ACorg ratios, which are either constant or variable with depth, on the estimate is assessed. Throughout the water column the horizontally mapped DICre m concentrations increase northward due to enlarged export fluxes of organic matter and subsequently enhanced remineralization processes as well as to the accumulation of remineralization products along the trajectory path of the water masses ventilating the Arabian Sea from the southern Indian Ocean. The choice of the remineralization ratios generates significant differences in the DICre m concentrations at specific depth horizons. The DICre m inventory of the Arabian Sea between 500 and 4500 m in the years 1995-1997 amounts to -39-44 Gt C depending on the applied remineralization ratios. IntroductionThe monsoon-forced nutrient supply to the mixed layer by coastal upwelling in the summer and vertical convection in the winter is the prime factor responsible for the high rates of primary and new production in the Arabian Sea