I. Introduction
The western rim of the confluence region of northern and southern hemisphere waters near 5°N becomes the head for the eastward flowing of the North Equatorial Countercurrent (NECC) in the westernmost equatorial Pacific. This current conveys the water masses supplied by relatively high salinity water originated in the extending and re-curving New Guinea Coastal Current (NGCC)/New Guinea Coastal Undercurrent (NGCUC) from the southern hemispheres, and relatively low salinity water originated in the Mindanao Current (MC) from the northern hemisphere. It influences significantly on salinity variation in the thermocline and intermediate water layers in and around the confluence region (Fine et al., 1994; Qiu et al., 1999; Kashino et al., 1996, 1999). Inside those re-curving currents region, two transient eddies are formed which are known as the clockwise Halmahera eddy (HE) and the anticlockwise Mindanao eddy (ME) (Fig. 1). It is suggested that the location and magnitude of these eddies may control properties of the inter-hemispheric transport and the composition of the water masses entering into the equatorial Pacific thermocline (Kashino et al., 1996; Wajsowicz, 1999); and may also have a significant contribution to development of the E1 Nino and Southern Oscillation (ENSO) and influence on variation of the Indonesian Throughflow (Webster and Lukas, 1992; Gordon, 1986).