Distribution of PARAFAC modeled CDOM components in the North Pacific Ocean, Bering, Chukchi and Beaufort Seas.

Abstract: The spatial and vertical distribution of colored dissolved organic matter (CDOM) in the North Pacific Ocean, Bering, Chukchi and Beaufort Seas was investigated with respect to water circulation. Four fluorescent components were identified in 546 samples using parallel factor analysis (PARAFAC): terrestrially-derived humic-like (C1), UV humic-like (C2), microbially derived humic-like (C3) and proteinaceous/tryptophan-like (C4) components. Deep water upwelling upon contact with the Aleutian Islands influenced optical properties of CDOM in Bering Sea surface water, where higher absorption coefficient at 355nm (a355), fluorescence intensities of all CDOM components and lower spectral slope (S275–295) were found compared to surface waters of the Gulf of Alaska (p<0.01). Further north, a marked increase in bioprocessed material (C4) was found in surface waters in Chukchi Sea. This finding was attributed to elevated biological activity in surface Chukchi water. Humic-like C1–C3 showed considerable dilution with increasing latitude from coastal to offshore regions in surface Beaufort Sea, suggesting a terrestrial predominance. This contrasts well with protein-like C4 where no significant gradient was found in Beaufort Sea surface water, supporting in situ generation. Finally, the vertical decrease of protein-like C4 relative to humic-like components C1–3 suggests that humic-like CDOM is produced at depth as a byproduct of remineralization. [Copyright &y& Elsevier]