Euphotic-zone nutrient algorithms for the NABE and EqPac study sites

Algorithms relating nutrient concentrations to density have been available for parts of the deep ocean for many years. Similar algorithms for the euphotic zone have proved to be elusive because of the relatively dynamic nature of nutrient and other processes there. However, if the hydrographic parameterization is recast to reflect these processes, remarkably good predictions of nutrient concentrations are possible. Regional examples and examples from the spring bloom in the North Atlantic, and for the El Niño and El Niña conditions in the central Pacific are presented. Nitrate concentrations can be predicted with a standard error of 0.5–1.0 μM or better. Possible applications of such algorithms include data QA/QC, retro-fitting and interpolating the nutrient data coverage of mooring and cruise data sets, and remote sensing and improved regional estimates of new production.