Marra¹, John, and Richard T. Barber²

¹Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, NY 10964 USA, Tel: 1-845-365-8891, Fax: 1-845-365-8150, E-mail: marra@ldeo.columbia.edu, and ²NSEES, Duke University, 135 Duke Marine Lab Road, Beaufort, NC 28516-9721

Primary productivity in the JGOFS era

Presented is a review of the observations of primary productivity from the process studies (NABE, EqPac, Arabian Sea, AESOPS) of JGOFS, along with an analysis of an evaluation of the ¹⁴C method and a means toward establishing the state of the global ocean in terms of its primary productivity. From an examination of the data, together with an analysis of isotopic uptake, it is concluded that the ¹⁴C technique measure net primary production. An algorithm for the calculation of primary productivity from space is presented, based on irradiance, the absorption of irradiance by phytoplankton, and the efficiency with which that irradiance is converted to fixed carbon. The absorption of irradiance by phytoplankton is evaluated based on recent measurements from the Sargasso Sea, the boreal North Atlantic, the Southern Ocean, and the Arabian Sea. It is found that the chlorophyll-specific absorption coefficient varies in a predictable way with sea-surface temperature, and this can be used to parameterize an optical characteristic of phytoplankton as a function of geographic location and season. Other algorithms are examined for their ability to predict in situ primary productivity, using data from the JGOFS process cruises.