Chemical evidence for the origin of the cold water belt along the northeastern coast of Hokkaido
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In the southwestern Okhotsk Sea, the cold water belt (CWB) is frequently observed on satellite images offshore of the Soya Warm Current flowing along the northeastern coast of Hokkaido, Japan, during summertime. It has been speculated that the CWB is upwelling cold water that originates from either subsurface water of the Japan Sea off Sakhalin or bottom water of the Okhotsk Sea. Hydrographic and chemical observations (nutrients, humic-type fluorescence intensity, and iron) were conducted in the northern Japan Sea and southwestern Okhotsk Sea in early summer 2011 to clarify the origin of the CWB. Temperature–salinity relationships, vertical distributions of chemical components, profiles of chemical components against density, and the (NO3 + NO2)/PO4 relationship confirm that water in the CWB predominantly originates from Japan Sea subsurface water.
KeywordsCold water belt Okhotsk Sea Japan Sea Chemical components Hydrographic data
We thank the scientists, technicians, captain, and crew of the T/S Oshoro-Maru of Hokkaido University for their help with water sampling. We are grateful to two reviewers for their constructive and helpful comments on this work. This study was supported partly by the Grant for Joint Research Program of the Institute of Low Temperature Science, Hokkaido University, and the Environment Research and Technology Development Fund of the Ministry of the Environment, Japan (A-1002).
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