Satellite-based sediment and chlorophyll a estimates for Lake Superior

Estimates of chlorophyll a and total suspended matter (TSM) concentrations are obtained from Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) imagery. We used a coastal atmospheric correction involving an iterative correction for absorbance in the near-infrared bands; however, most scenes had negative radiances at 412 nm, necessitating application of a form of absorbing aerosol correction. An empirical relationship between remote sensing reflectance at 555 nm and TSM concentrations was established, with linear covariance R-2 = 0. 74. The NASA coastal bio-optical algorithm (OC2-V2) for chlorophyll a had strong co-variance with ground-based chlorophyll a (R-2 = 0.87), but with a 3-fold overestimate in chlorophyll a concentration. Satellite-based chlorophyll a concentrations (C-OC2) were corrected based on the regression equation to provide a new solution as follows: C-OC2(transform) = 0.3(C-OC2-0.4). The overall result for Lake Superior is a regional chlorophyll a algorithm, analogous to algorithms that have been developed for other coastal regions of the U.S.