Bio-optical properties and remote sensing ocean color algorithms for Antarctic Peninsula waters

Increasing evidence suggests that bio-optical properties of Antarctic waters are significantly different than those at temperate latitudes. Consequently, retrieval of chlorophyll concentrations from remotely sensed reflectance measurements using standard ocean color algorithms are likely to be inaccurate when applied to the Southern Ocean. Here we utilize a large bio-optical data set (>1000 stations) collected in waters west of the Antarctic Peninsula in conjunction with the Palmer Long Term Ecological Research program to assess ocean optical properties and associated ocean color algorithms. We find that the remote sensing reflectance spectrum as a function of chlorophyll concentrations appears significantly different from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Bio-optical Algorithm Mini-workshop data set collected from other regions of the world's oceans. For Antarctic waters, remote sensing reflectance is significantly higher in the blue region and lower in the green region of the spectrum for high chlorophyll concentrations (>1 mg Chi m(-3)). Therefore applying general processing algorithms for both Coastal Zone Color Scanner and SeaWiFS in these Antarctic waters results in an underestimate of chlorophyll by roughly a factor of 2. From modeled estimates of absorption and backscattering we hypothesize that both low chlorophyll-specific absorption and low backscattering contribute to the high reflectance ratios.