Predictive bio-optical relationships for polar oceans and marginal ice zones

Mitchell, B.G., 1992. Predictive bio-optical relationships for polar oceans and marginal ice zones. J. Mar. Syst., 3: 91-105. An analysis of more than 500 stations from polar seas was undertaken to evaluate predictive models linking in situ phytoplankton pigment concentrations to measurable optical parameters. The data set consists of profiles of spectral downwelling irradiance [Ed(A], upwelling radiance [Lu(A)], chlorophyll and phaeopigments from 3 cruises to the Antarctic Peninsula (RACER, UVDOZ-88, UVDOZ-89), one cruise to the Barents Sea (PRO MARE) and one cruise to Fram Strait in the Greenland Sea (CEAREX). The pigment specific diffuse attenuation coefficient [Kd*()t) m 2 mg -1 chl a +phaeo] for polar regions is significantly smaller, particularly in the blue region of the spectrum, than previous statistical models for temperate oceans predict. Consistent with the observations for Kd*(A), phytoplankton remote sensing pigment retrieval algorithms, based on Lu(A), show significant differentiation from temperate ocean models. The presently recommended water-leaving radiance algorithm for Coastal Zone Color Scanner data processing underestimates surface pigment concentrations by more than a factor of two for the polar observations reported here. The observations are interpreted in the context of variations in pigment specific particulate absorption [a*(A) m 2 mg -1 chl a +phaeo] which have been described elsewhere. Specifically, the magnitude of a~'(A) in the blue is hypothesized to be smaller for polar regions due to significant pigment packaging effects, and a relatively small amount of detrital absorption compared to phytoplankton absorption. Implications for remote sensing of phytoplankton pigments and pigment-based models of light propagation in the oceans are discussed.