Journal of Oceanography, Vol. 65 (No. 1), pp. 1-16, 2009
Yuko Ohno1,2, Naoto Iwasaka1,3*, Fumiaki Kobashi1 and Yoshiko Sato1,4
1Tokyo University of Marine Science and Technology, Koto-ku, Tokyo 135-8533, Japan
2Kisarazu National College of Technology, Kiyomidaihigashi, Kisarazu-shi, Chiba 292-0041, Japan
3Institute of Observational Research for Global Change, JAMSTEC, Natsushima-cho, Yokosuka-shi, Kanagawa 237-0061, Japan
4Shinko Co. Ltd., Mimamishinagawa, Shinagawa-ku, Tokyo 140-0004, Japan
(Received 8 January 2008; in revised form 19 July 2008; accepted 19 July 2008)
Abstract: A monthly mean climatology of the mixed layer depth (MLD) in the North Pacific has been produced by using Argo observations. The optimum method and parameter for evaluating the MLD from the Argo data are statistically determined. The MLD and its properties from each density profile were calculated with the method and parameter. The monthly mean climatology of the MLD is computed on a 2° × 2° grid with more than 30 profiles for each grid. Two bands of deep mixed layer with more than 200 m depth are found to the north and south of the Kuroshio Extension in the winter climatology, which cannot be reproduced in some previous climatologies. Early shoaling of the winter mixed layer between 20-30°N, which has been pointed out by previous studies, is also well recognized. A notable feature suggested by our climatology is that the deepest mixed layer tends to occur about one month before the mixed layer density peaks in the middle latitudes, especially in the western region, while they tend to coincide with each other in higher latitudes.