East-West Distribution of Nutrients and Dissolved Inorganic Carbon in the Northern North Pacific in Autumn

ABSTRACT

We measured nutrient and dissolved inorganic carbon (DIC) concentrations from west to east across the northern North Pacific Ocean from station K2 to Ocean Station Papa during September and October 2005. At 2000 m depth, silicate levels increased and dissolved oxygen levels decreased from west to east. This trend was attributed to seawater in the layer flowing from west to east in the northern North Pacific. Distributions of normalized (salinity = 33) nutrients and DIC showed the general trend of “west high, east low” (WHEL) in the surface layer. Normalized nitrate and DIC concentrations above 30 m depth ranged from 7 to 13 μmol kg-1 and from 2027 to 2045 μmol kg-1, respectively. Seasonal drawdowns of nutrients and DIC from winter to autumn showed the WHEL trend, similar to previous studies. The ratio of silicate drawdown to nitrate + nitrite drawdown also showed the WHEL trend, which might result from longitudinal differences in the proportion of diatoms in the phytoplankton community in the northern North Pacific.