Bio-optical properties of seawater in the Western subarctic Gyre and Alaskan Gyre in the subarctic North Pacific and the Southern Bering Sea during the summer of 1997

Chlorophyll a concentrations (chl a) and the absorption coefficients of total particulate matter [ap(λ)], phytoplankton [aph(λ)], detritus [ad(λ)], and colored dissolved organic matter: CDOM [aCDOM(λ)] were measured in seawater samples collected in the subarctic North Pacific and the southern Bering Sea during the summer of 1997. We examined the specific spectral properties of absorption for each material, and compared the light fields in the Western subarctic Gyre (area WSG) with those in the Alaskan Gyre (area AG), and the southern Bering Sea (area SB). In the area WSG, the irradiance in the surface layer decreased markedly, indicating high absorption. In the area AG, the radiant energy penetrated deeply, and the chl a and absorption values were low throughout the water column. In the area SB, light absorption was high in the surface layer on the shelf edge and decreased with increasing depth; on the other hand, light absorption was low in the surface layer in the shelf area and increased with increasing depth.