| Institution: | (1) Hokkaido National Fisheries Research Institute, Katsurakoi, Kushiro 085-0802, Japan;(2) Meteorological Research Institute, Nagamine, Tsukuba 305-0052, Japan;(3) Hakodate Marine Observatory, Mihara, Hakodate 041-0806, Japan;(4) Kobe Marine Observatory, Wakihama-kaigandori, Chuo-ku, Kobe 651-0073, Japan;(5) Graduate School of Environmental Earth Science, Hokkaido University, Chuo-ku, Sapporo 060-0810, Japan;(6) National Research Institute of Fisheries Science, Fukuura, Kanazawa-ku, Yokohama 236-8648, Japan;(7) Present address: 1-15-422 Minai-7, Nishi-23, Chuo-ku, Sapporo 064-0807, Japan |
| Abstract: | Eight-year observation results of DIC from 1996 to 2003 in the Oyashio region have been analyzed to obtain a climatological
view of its seasonal variation and interannual variation. Data of DIC obtained by several institutes are synthesized to give
a dataset with an uncertainty lower than 5 μmol/kg. The obtained climatology of NDIC seasonal variation in the Oyashio mixed layer shows a seasonal amplitude of 176 μmol/kg, with a maximum in January and a minimum in September. These features closely resemble those observed in the southern
half of the western subarctic North Pacific (WSNP) including Station KNOT, although the timing of the NDIC maximum is slightly
advanced in the case of the Oyashio. Analysis using a quasi-conservative tracer Cp0 (NDIC - 106NP) shows that among 176 μmol/kg of NDIC seasonal variation, only 16 μmol/kg is attributed to hydrographic processes while the remaining 160 μmol/kg is attributed to biological processes. The Cp0 value in the Oyashio mixed layer also resembles that of the WSNP mixed
layer during the months May to November, suggesting further resemblance of the Oyashio water mass to that of WSNP in terms
of carbon dynamics. The present results also suggest that a single data obtained in Oyashio mixed layer contains 30 μmol/kg of potential uncertainty for the representativity of this region, which leads to a note about a need to treat with
caution results obtained by a single observation in this region. |
