APPLICATION OF STOCHASTIC METHODS TO THE MODELING OF NONLINEAR RELATIONSHIPS BETWEEN OCEAN PRODUCTIVITY, VENTILATION, AND ATMOSPHERIC COMPOSITION

There are abundant data indicating that phosphorus retention in marine sediments is strongly controlled by bottom water O2 concentration: anoxic bottom waters promote the regeneration of organic phosphorus, leading to a decrease in the net burial rate (Van Cappellen and Ingall 1994, 1996). A central parameter mediating the feedback between bottom water oxygen, phosphorous, and atmospheric oxygen concentrations is the ventilation rate. In addition to its importance in terms of episodic coastal eutrophication, the relationship between the ventilation rate and the thermal structure of the global ocean has important implications for the long term phosphorous cycle as well (e.g., Wallman 2003). Here we examine the relationship between ventilation, productivity, ocean and atmospheric composition over time scales of ten of thousands to millions of years using a simplified stochastic approach. This approach allows an efficient evaluation of system sensitivity with respect to temperature, ocean mixing rate, net productivity and ocean/atmosphere composition. In the study of perturbed states, this efficiency becomes particularly important for separating issues related to numerical stability of the model itself versus physical sensitivity of the system.