Seasonal and Interannual Variability in the Distribution of Surface Nutrients and Dissolved Inorganic Carbon in the Northern North Pacific: Influence of El Niño |
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| Authors: | Chi Shing Wong Nathalie A D Waser Yukihiro Nojiri Wm Keith Johnson Frank A Whitney John S C Page Jiye Zeng |
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| Institution: | (1) Institute of Ocean Sciences, Centre for Ocean Climate Chemistry, P.O. Box 6000, Sidney, B.C., V8L 4B2, Canada;(2) Department of Earth and Ocean Sciences, University of British Columbia, 6270 University Boulevard, Vancouver, B.C., V6T 1Z4, Canada;(3) National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan;(4) c/o National Institute for Environmental Studies, Global Environmental Forum Foundation, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan |
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| Abstract: | The seasonal and interannual changes in surface nutrients, dissolved inorganic carbon (DIC) and total alkalinity (TA) were recorded in the North Pacific (30–54°N) from 1995 to 2001. This study focuses on the region north of the subarctic boundary (～40°N) where there was extensive monthly coverage of surface properties. The nutrient cycles showed large interannual variations in the eastern and western subarctic gyres. In the Alaska Gyre the seasonal depletion of nitrate (ΔNO3) increased from 8–14 µmol kg?1 in 1995–1999 to 21.5 µmol kg?1 in 2000. In the western subarctic the shifts were similar in amplitude but more frequent. The large ΔNO3 levels were associated with high silicate depletions, indicating enhanced diatom production. The seasonal DIC:NO3 drawdown ratios were elevated in the eastern and central subarctic due to calcification. In the western subarctic and the central Bering Sea calcification was significant only during 1997 and/or 1998, two El Niño years. Regional C/N stoichiometric molar ratios of 5.7 to 7.0 (>40°N) were determined based on the years with negligible or no calcification. The annual new production (NPa) based on ΔNO3 and these C/N ratios showed large interannual variations. NPa was usually higher in the western than in the eastern subarctic. However, values of 84 gC m?2yr?1 were found in the Alaska Gyre in 2000 which is similar to that in the most productive provinces of the northern North Pacific. There were also large increases in NPa around the Alaska Peninsula in 1997 and 1998. Finally, the net removal of carbon by the biological pump was estimated as 0.72 Gt C yr?1 in the North Pacific (>30°N). |
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| Keywords: | Dissolved inorganic carbon nitrate seasonal cycles new production interannual variations |
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