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Satellites routinely provide frequent, large‐scale, near‐surface views of many oceanographic variables pertinent to plankton ecology, but nutrient fertility remains problematic. A recently derived set of nitrate (N), phosphate (P), and silicate (S) nutrient depletion temperatures (NDT) were subtracted from AVHRR‐derived sea surface temperatures for March 1999 through June 2000 to determine eight categories of temporally varying N, P, and S presence/absence in the world ocean. Complementary midmonth, aerosol optical thickness (70°N to 70°S) and precipitation (40°N to 40°S), obtained from the AVHRR Pathfinder effort and the TRMM microwave imager, respectively, represented iron (F) presence (>10%)/absence (<10%) in the world ocean as dry and wet (40°N to 40°S) or just dry (40°N–70°N and 40°S–70°S) deposition of atmospheric dust. The resulting 16 N, P, S, and F presence/absence categories provided a dynamic view of seasonal and interannual nutrient variability in the world ocean. SeaWiFS chlorophyll a maps for April, July, and October 1999 and January 2000 were compared to the N, P, S, and F categories from these months. Phytoplankton cell size and taxonomic composition categories linked to each of the 16 nutrient availability categories translated the nutrient associations with chlorophyll a into an inferred phytoplankton community structure. Consideration of additional bottom‐up (like solar irradiance exposure) and top‐down (like grazing by zooplankton) influences on size and species/class specific net phytoplankton growth can improve the assignment of inferred phytoplankton community structure. The proposed dynamic approach toward monitoring nutrient availability can contribute to refined estimates of biogeochemical fluxes in the world ocean.

Nitrogen is the most broadly limiting factor for marine phytoplankton on ecological timescales. Nitrate, as the most oxidized inorganic species, plays a significant role in nitrogen availability based on nutrient flux to the euphotic zone from deeper waters, and is a major determinant of new production. Increased new production relates to higher trophic level abundance and to carbon dioxide drawdown from the atmosphere. The present work is the first stage in the development of a technique to generate a scaled index of nitrate availability in the surface waters of the global ocean using satellite‐derived temperature data. The technique currently involves a fixed matrix of nitrate depletion temperatures (NDT) and remotely‐sensed sea surface temperature (SST) from the monthly‐averaged AVHRR Pathfinder series. The magnitude of the difference between these two temperatures at a given location indicates the degree of nitrate presence or absence. Graded monthly nitrate presence/absence maps over a 10‐year period were created based on the size of the difference between these two temperatures. A 10‐year average of these differences exhibits major nitrate distribution features similar to those observed in maps based on National Oceanic Data Center archived measurements. In contrast, monthly nitrate maps provide a unique and dynamic representation of nitrate availability in the global ocean. This nutrient monitoring capability based on remotely sensed data can contribute to the estimation of new production in the global ocean, improving management of various world fisheries and improving estimation of the atmospheric draw down of carbon dioxide, a major greenhouse gas.

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