The Role of Ecosystem Dynamics on the Global Ocean Carbon Cycle: A JGOFS Model-Data Synthesis

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This project seeks to better quantify the role of marine ecosystem dynamics on the global ocean carbon cycle, focusing in particular on air-sea CO2 exchange, net community production, and vertical export. The research is motivated by two related hypotheses: multi-nutrient limitation (N, P, Si, Fe) modulates phytoplankton biomass and primary production, community structure, and biogenic carbon export, community structure governs the elemental composition of the exported dissolved and particulate material, major determinants of subsurface biogeochemical transport, remineralization, and sequestration. In this project a carefully designed set of numerical experiments will be run using a global 3-D coupled ecological-biogeochemical-physical model. The project directly builds upon recent progress and specific findings/questions from a global mixed layer ecosystem model that includes explicit iron limitation and community structure, a full depth 3-D ocean carbon cycle model, and historical hind-cast simulations (1958-1997) of ocean physical circulation Specifically, the goals of the activity are to: o Complete development of a next generation, global 3-D ecological-biogeochemical-physical model that includes multi-nutrient limitation and explicit geochemical functional groups (picoplankton, diatoms, Trichodesmium, and coccolithophores).o Evaluate and iteratively improve on the simulated upper ocean ecosystem dynamics against regional JGOFS data sets, large-scale surface pCO2 and nutrient fields, and satellite ocean color data using retrospective, historical simulations for the period 1988-2000.o Assess the skill of the resulting model in replicating the full depth, equilibrium distributions of carbon, oxygen and nutrients against the WOCE/JGOFS global survey data.o Test the ecological and biogeochemical impact of dust deposition, calcification, nitrogen fixation, and silica production by selective modifications to the base coupled solution.The study directly addresses the overall goal of the U.S. JGOFS Synthesis and Modeling Project (SMP), to synthesize present knowledge into global numerical models that can be used for prediction, as well as two of the major research trajectories highlighted in the SMP program announcement: "global and regional studies that link together the biological, physical, and chemical components of the marine carbon cycle" and "synthesis and modeling efforts that effectively combine field data sets and diagnostic and prognostic (forward) models".