The path of the Kuroshio Extension describes two stationary meanders with crests at approximately 144°E and 150°E. The short-term meridional fluctuations of the warm water spreading northward from the first crest at the surface and its vertical structure were analyzed by using 5-day-mean surface temperature maps published by JAFIC, montly 100-m-depth temperature maps edited by the JMA, and CTD data obtained by the R.Vs.Kofu-Maru, Hakuho-Maru andTansei-Maru cruises from 1990 to 1994. A Northern Boundary of the Spreak Kuroshio Water (NBSKW) and a Southern Boundary of the Spread Kuroshio Water (SBSKW) at the surface were defined as the northern and southern boundary of the pronounced meriodional temperature gradients, respectively. The vertical structure of the Spread Kuroshio Water was analyzed in terms of its T-S properties. The location of the NBSKW at the surface corresponds well with the northern boundary of the subsurface high salinity water that represents the Spread Kuroshio Water. The short-term meridional fluctuations of the northern and southern boundary of the Spread Kuroshio Water at the surface were studied through the spectral analysis of the maximum latitude of the two lines defined. We obtained the following results: (1) the meridional fluctuations of the NBSKW and SBSKW at the first creast have major periods between 16 and 38 days; (2) the 50 day running mean of the SBSKW at the first crest, for the purpòse of this study, can be generally used as indicative of the location of the Kuroshio axis; and (3) the northward extent of the Spread Kuroshio Water and the velocity of the meridional shift suggest seasonal variability that could be related with their vertical structure.
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