Isotopic tracers for water masses in the coastal region of eastern Hokkaido
- 169 Downloads
In this study we used two stable isotopes, δ13C and δ18O, for water mass classification in the coastal region off eastern Hokkaido. δ13C* values, which were corrected for the biological effect, and δ18O values up to 300 m depth suggested that the isotopic character of the onshore and offshore water in the southern Okhotsk Sea, the Nemuro Strait and the western North Pacific could be explained by the mixing of three source waters: the Oyashio water (OYW), Soya Warm Current water (SWCW) and East Sakhalin Current water (ESCW). In summer, δ13C*-δ18O plots indicated mixing between SWCW from the southern Okhotsk Sea and OYW in the Pacific coast of southeastern Hokkaido, while temperature-salinity plots of the onshore water showed minimal difference from the offshore OYW. In winter, on the other hand, the mixed water of ESCW and OYW (or SWCW) appeared in the Pacific coastal region, distributed as cold, low salinity onshore water. Finally, we estimated mixing ratios of OYW, SWCW and ESCW in the coastal region of western North Pacific using their mean values of δ13C* and δ18O as endmembers. These results suggest seasonal and yearly changes of water mass combination en route from the southern Okhotsk Sea to the western North Pacific.
KeywordsStable isotopes Soya Warm Current water East Sakhalin Current water Oyashio water southern Okhotsk Sea western North Pacific eastern Hokkaido
Unable to display preview. Download preview PDF.
- Biebow, N., E. Hütten and K. Wallmann (2001a): Water chemistry at station LV28-14-1, PANGAEA, doi:10.1594/PANGAEA.64753.Google Scholar
- Biebow, N., E. Hütten and K. Wallmann (2001b): Water chemistry at station LV28-43-1, PANGAEA, doi:10.1594/PANGAEA.64761.Google Scholar
- Biebow, N., E. Hütten and K. Wallmann (2001c): Water chemistry at station LV28-61-1, PANGAEA, doi:10.1594/PANGAEA.64764.Google Scholar
- Fujii, K. and Y. Sato (1979): Productivity and oceanographic structure in the coastal waters of the Japan Sea and Okhotsk Sea coasts of Hokkaido. Bull. Japanese Soc. Fish. Oceanogr., 34, 57–62 (in Japanese).Google Scholar
- Kitani, K. (1973): An oceanographic study of the Okhotsk Sea—particularly in regard to cold waters. Bull. Far Seas Fish. Res. Lab., 9, 45–77.Google Scholar
- Kusaka, A., T. Ono, T. Azumaya, H. Kasai, S. Oguma and Y. Kawasaki (2007): Seasonal variation of ocean structure in the Pacific coastal region of eastern Hokkaido. Bull. Coastal Oceanogr. (in Japanese with English abstract) (in preparation).Google Scholar
- Matsuyama, M., M. Aota, I. Ogasawara and S. Matsuyama (1999): Seasonal variation of Soya Current. Umi no Kenkyu, 8(5), 333–338 (in Japanese with English abstract).Google Scholar
- Mook, W. G. and F. C. Tan (1991): Stable carbon isotopes in rivers and estuaries. In SCOPE 42, Biogeochemistry of Major World Rivers, ed. by E. T. Degens, S. Kempe and J. E. Richey, ICSU SCOPE Series online library (https://doi.org/www.icsu-scope.org).
- Ogasawara, J. (1990): The eastern and southern coastal region of Hokkaido. II. Physics. In Coastal Oceanography of Japan Islands (Supp. Vol.), ed. by Coastal Oceanography Research Committee, The Oceanographic Society of Japan (in Japanese).Google Scholar
- Oguma, S., Y. Kawasaki and T. Azumaya (2007): Water mass variation process in the Nemuro Strait during spring and autumn. Umi no Kenkyu, 16, 361–374.Google Scholar
- Ohtani, K. (1989): The role of the Sea of Okhotsk on the formation of the Oyashio water. Umi to Sora, 65(2), 63–83 (in Japanese with English abstract).Google Scholar
- Parsons, T. R., Y. Maita and C. M. Lalli (1984): A Manual of Chemical and Biological Methods for Seawater Analysis. Pergamon Press, Oxford, 173 pp.Google Scholar
- Schmidt, G. A., G. R. Bigg and E. J. Rohling (1999): Global Seawater Oxygen-18 Database. https://doi.org/data.giss.nasa.gov/o18data/
- Watanabe, K. (1963): On the reinforcement of the East Sakhalin Current preceding to the sea ice season off the coast of Hokkaido-study on sea ice in the Okhotsk Sea (IV). Oceanogr. Mag., 14, 117–130.Google Scholar