Regional variations in bio-optical properties of the surface waters in the Southern Ocean

Values of attenuation coefficient, Kd(λ), for five visible wavelengths are reported for 14 sites around South Georgia and the Bransfield Strait, in the Southern Ocean. The mean chlorophyll-plus-phaeopigment concentrations in the upper 30 m of the water column ranged from 0.32–6.633 mg m−3 with one particularly high mean value of 31 mg m−3. Partition of attenuation between chlorophyll (Kc) and other factors in the water column (Ko) indicated that the spectral character of Ko in the Bransfield Strait was consistent with absorption by non chlorophyll-like pigments (Gelbstoff). Values were significantly different between the two areas. Values of the specific attenuation coefficient due to pigment concentration (Kc) were small compared to temperate values. These data support other studies in suggesting that the application of remotely sensed ocean colour data to global biogeochemical surveys requires the development of regional algorithms.