How high will future concentrations of atmospheric greenhouse gases be? How long will atmospheric concentrations remain elevated if emissions decrease? Answering these important questions depends on a thorough understanding of biogeochemical cycles.

The most abundant greenhouse gases resulting from human activities (e.g., CO₂, CH₄, and N₂O) are also naturally occurring compounds. These compounds cycle between the ocean and atmosphere, often through biological intermediaries. Through these biogeochemical cycles, the compounds are partitioned between relatively harmless phases, like tree trunks or bicarbonate ions in the ocean, and potentially harmful phases, like elevated stocks of atmospheric CO₂.

Princeton University and GFDL scientists maintain active research programs to understand these biogeochemical cycles. Jorge Sarmiento and J. R. Toggweiler lead intensive research efforts aimed at modeling the carbon cycle -- including its oceanic, atmospheric, and terrestrial components -- and evaluating the uptake of anthropogenic CO₂ by the ocean.

GFDL scientists are also making use of certain chemical species as tracers of the ocean circulation (e.g., CFCs and radiocarbon). By studying tracer distributions in the ocean, they are attempting to assess the ocean's potential to take up heat from the atmosphere, an important part of the greenhouse warming problem.

Observed (top) and model-simulated (bottom) distribution of surface nitrate concentrations (in mmol m**-3) in the tropical Pacific Ocean. The model prediction is produced by a model, developed at GFDL and Princeton University, that incorporates ocean dynamics and a simple ecosystem. The focus of the work is on upwelling in the central equatorial Pacific and its effect on surface nutrient levels, biological activity, and biogeochemical cycles. The ecosystem model is not designed to simulate biological activity near continental margins, hence the overprediction of nitrate along the coast of South America.