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Optical properties of colored dissolved organic matter (CDOM) were investigated along a latitudinal transect (67°–77° N) in upper water (<80 m depth) of the western Arctic Ocean. The absorption coefficient at 280 nm was 0.48–1.25 m−1, with the average for the oligotrophic basin area (1.04 ± 0.08 m−1) being slightly higher than that of the productive shelf area (0.95 ± 0.16 m−1), implying a decoupling effect between CDOM concentration and biological productivity in the western Arctic Ocean. The spectral slope coefficient S270–350 was negatively correlated with salinity, indicating that DOM molecular weight increases with salinity, and may be affected by melt-water input. Four fluorescent components were identified by excitation emission matrices elaborated by parallel factor analysis, including three humic-like (C1, C3, and C4) components and one protein-like (C2) component. Significant increases in concentrations of terrestrially derived humic-like C3 and C4 components with salinity were observed in the basin, mainly controlled by the physical mixing of surface fresh water and subsurface inflowing Pacific Ocean water. Terrestrial material carried by Pacific inflow is thus an important factor affecting the distribution of CDOM fluorescence components. The C3 and C4 fluorescence components may be useful as tracers of Pacific water in the western Arctic Ocean. [ABSTRACT FROM AUTHOR]

Nutrient data were collected along similar cross-basin transects in the Canada Basin (75°–85°N) in 2005–2008, to evaluate the long-term change in the nitrate deficit. The results revealed a subsurface N* minimum (<−10 μmol/kg), indicating a large nitrate deficit in the upper halocline water of the basin. The interannual change of N* from 2005 to 2008 demonstrates the increase in the nitrate deficit. The subsurface low-N* waters are expanding, especially in the southern Canada Basin (75°–80°N). The thickening distribution of Pacific water is primarily responsible for the expansion of the nitrate deficit in the basin. • Large nitrate deficit (N* < −10 μmol/kg) in the Canada basin. • Subsurface low-N* waters are expanding, especially in the southern Canada Basin. • Thickening Pacific water distribution is increasing the nitrate deficit. [ABSTRACT FROM AUTHOR]