For the ECMWF-based wind stresses, the southern extent of the northern tropical gyre lies just to the south of the Philippines at about 5｡?, whereas for Hellerman & Rosenstein data, it lies just to the north of Irian Jaya at about 1｡?, i.e. at the opposite end of the entrance to the Indonesian seas. Fig. 3 shows the variation in Sverdrup streamfunction at the west Pacific coast as a function of time and latitude calculated from Florida State University (FSU) wind stresses with a 3-year running mean applied. There is considerable variation in the latitude of the zero streamfunction contour, and the general northward shift over the last 30 years is consistent with the differences described between the Hellerman & Rosenstein (1983) and ECMWF 1987-1995 mean data.
(a)
(b)
Fig. 2 Contour maps for the maritime continent of the Sverdrup streamfunction calculated from (a) Hellerman & Rosenstein (1983) and (b) ECMWF 1987-1995 wind-stress climatologies are shown. The island rule has been used to determine the streamfunction value on each island represented. The contour interval is 5 Sv. Solid (dashed) lines denote positive (negative) contour, and a dot-dash line denotes the zero contour.
Fig. 3 The Sverdrup streamfunction, calculated from FSU wind stresses, at the interior edge of the Pacific western boundary layer is contoured as a function of time and latitude. The contour interval is 5 Sv. Solid (dashed) lines denote positive (negative) contours, and a dot-dash line denotes the zero contour.
