Bio‐optical provinces of the Northeast Pacific Ocean: A provisional analysis.

Abstract

A provisional analysis of satellite ocean color imagery and in situ profiles of spectral irradiance and Chl a fluorescence partitions the Northeast Pacific Ocean into four geographically and bio‐optically distinct provinces: the California Current system, the Alaskan gyre, the east central North Pacific central gyre, and the subarctic front. Within each province in a given 2‐month period (June– July 1985 and October–November 1982), a family of regression equations was found to accurately predict the vertical profiles of irradiance attenuation and normalized Chl a fluorescence from K490—the surface diffuse attenuation coefficient which can be estimated from remotely sensed ocean color. The irradiance attenuation profile (to the depth where irradiance is 0.1% of the surface value) is predicted directly from the reciprocal of K490. Prediction of the Chl a fluorescence profile is based on a log‐linear photoadaptive profile of fluorescence over diffuse optical depth—a conceptual model which robustly fit the entire sample analyzed. Given K490, the profile is determined from four regression models predicting the depth in meters of the fluorescence maximum, the optical depth of the deep background fluorescence minimum, the surface intercept of the profile, and the slope of the profile between the surface and maximum.