Friday 26 August 2005

P2
1050-1230 hours

460
A centennial time series of core layer temperature of North Pacific Subtropical Mode Water
Suga, Toshio¹, Abe, Masahiko¹, Hanawa, Kimio¹, Watanabe, Tomowo²
1 Graduate School Of Science, Tohoku University, Sendai, Japan
2 National Research Institute of Fisheries Science, Japan
Author email: suga@pol.geophys.tohoku.ac.jp
A nearly centennial time series of the core layer temperature (CLT) of North Pacific Subtropical Mode Water (NPSTMW) from 1921 to 2004 is constructed using all available temperature profiles archived in Japan Fisheries Oceanography Database (JFOD), Japan Oceanographic Data Center (JODC) hydrographic database and World Ocean Database (WOD) 2001. JFOD contains newly digitized hydrographic data collected by Japanese fisheries agencies from 1921 to 1952, which complements the JODC database and WOD fairly well. CLT is defined as the temperature of the layer having the minimum vertical temperature gradient at an individual profile, with temperature ranging from 15-degrees to 19-degrees-C. Annual mean CLT is calculated using all CLT data taken from May to December for the 5-degrees x 10-degrees (lat. X lon.) region from 30-degrees to 35-degrees-N and from 140-degrees to 150-degrees-E. The CLT time series shows long-term trend as well as decadal to interdecadal variation and interannual variation. Relationships are investigated among several atmospheric circulation indices, the Kuroshio transport, and CLT. The results confirm the former notion by Hanawa and Kamada (GRL, 2001), which is based on the shorter record from 1957 to 1996, that CLT might be crucially influenced by the Kuroshio transport in a time frame longer than ten years, and by the wintertime East Asian Monsoon in shorter time frames. The warming trend in CLT with the magnitude of 0.65-degrees-C per 100 years is partly explained by the weakening trend in the wintertime East Asian Monsoon and the strengthening trend in the Aleutian Low.

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