A new vision of ocean biogeochemistry after a decade of the Joint Global Ocean Flux Study (JGOFS)

The Joint Global Ocean Flux Study (JGOFS) has completed a decade of intensi ve process and time-series studies on the regional and temporal dynamics of biogeochemical processes in five diverse ocean basins. Its field program a lso included a global survey of dissolved inorganic carbon (DIC) in the oce an, including estimates of the exchange of carbon dioxide (CO2) between the ocean and the atmosphere, in cooperation with the World Ocean Circulation Experiment (WOCE). This report describes the principal achievements of JGOFS in ocean observat ions, technology development and modelling. The study has produced a compre hensive and high-quality database of measurements of ocean biogeochemical p roperties. Data on temporal and spatial changes in primary production and C O2 exchange, the dynamics of of marine food webs, and the availability of m icronutrients have yielded new insights into what governs ocean productivit y, carbon cycling and export into the deep ocean, the set of processes coll ectively known as the "biological pump." With large-scale, high-quality data sets for the partial pressure of CO2 in surface waters as well for other DIC parameters in the ocean and trace gas es in the atmosphere, reliable estimates, maps and simulations of air-sea g as flux, anthropogenic carbon and inorganic carbon export are now available . JGOFS scientists have also obtained new insights into the export flux of particulate and dissolved organic carbon (POC and DOG), the variations that occur in the ratio of elements in organic matter, and the utilization and remineralization of organic matter as it falls through the ocean interior t o the sediments. JGOFS scientists have amassed long-term data on temporal variability in the exchange of CO2 between the ocean and atmosphere, ecosystem dynamics, and carbon export in the oligotrophic subtropical gyres. They have documented s trong links between these variables and large-scale climate patterns such a s the El Nino-Southern Oscillation (ENSO) or the North Atlantic Oscillation (NAO). An increase in the abundance of organisms that fix free nitrogen (N -2) and a shift in nutrient limitation from nitrogen to phosphorus in the s ubtropical North Pacific provide evidence of the effects of a decade of str ong El Ninos on ecosystem structure and nutrient dynamics. High-quality data sets, including ocean-color observations from satellites, have helped modellers make great strides in their ability to simulate the biogeochemical and physical constraints on the ocean carbon cycle and to ex tend their results from the local to the regional and global scales. Ocean carbon-cycle models, when coupled to atmospheric and terrestrial models, wi ll make it possible in the future to predict ways in which land and ocean e cosystems might respond to changes in climate.