Tracer-based inferences of new and export primary productivity in the ocean
Additional Document Info
Obtaining regional estimates of seasonal to decadal average hew productivity in the ocean is an important goal. Tracer studies have proven useful in making such determinations, although the nature of the estimates made are colored by the character and space/time scales of the tracer systems used. These differences provide important clues as to mechanisms and processes. Knowledge of new, export and particulate export fluxes are powerful constraints for biogeochemical models. We have made significant advances over the past four years, with different tracer systems yielding more or less consistent results in, for example, the subtropical North Atlantic. The general agreement between essentially independent approaches does much to build our confidence in the veracity of their results. Further, exciting new insights are provided by new information regarding the relative magnitude of particulate export flux. Some nagging concerns remain, however, both due to the mismatch between these measurements and other more traditional approaches (e.g., sediment traps), and some unresolved implications of some of the observations. With improved measurement techniques, more sophisticated interpretive tools, and the large field programs in progress, we have high hopes that the future will bring a clearer view.