We thank Prof. Kimio Hanawa and other members of the Physical Oceanography Group, Tohoku University, for helpful comments and useful discussion. Comments from two anonymous reviewers greatly improved the manuscript. Most of the WOCE data were obtained through the WOCE Hydrographic Programme Office. Dr. M. J. McPhaden kindly provided the CTD data collected by NOAA/PMEL. This study was made as part of Subarctic Gyre Experiment (SAGE), which was financially supported by the former Science Technology Agency and the present Ministry of Education, Culture, Sports, Science, and Technology. This work was supported in part by funds from cooperative program (No. 7, 2001) provided by Ocean Research Institute, University of Tokyo. TS was supported by the Japan Society for Promotion of Science [Grant-in-Aid for Scientific Research (B), No. 13440138]. AMM was supported by NSF Grant OCE-0223421 and NOAA/CICOR Cooperative Agreement NA17RJ1223.
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