THE SOUTHWARD INTRUSION OF NORTH PACIFIC INTERMEDIATE WATER ALONG THEMINDANAO COAST

A tongue of low salinity intermediate water was observed along the coa st of Mindanao during the WEPOCS III experiment in June and July 1988. The tongue, delineated by a discontinuity in theta-S relations, is a southward intrusion of water at 26-27 sigma(theta). It is the Northern Hemisphere counterpart of the northward flow of Antarctic Intermediat e Water in the New Guinea Coastal Undercurrent, In the WEPOCS III data , it is seen entering the Celebes Sea near 5 degrees N at the southern tip of Mindanao. Once it passes the southern tip of Mindanao, it circ ulates within the Celebes Sea. Relatively fresh water at 26.55 sigma(t heta) is seen continuing-to flow toward the Makassar Strait and into t he Indonesian Throughflow, although some fraction mixes with intermedi ate water of equatorial Pacific and South Pacific origin and flows eas tward in the northern subsurface countercurrent. The tongue is present in a number of sections along 8 degrees N in the Mindanao Current, bu t it is often wider than is found in the WEPOCS III sections as measur ed by the distance from the Mindanao coast to the high horizontal sali nity gradient edge of the tongue. The tongue plays a part in the excha nge of water at intermediate density between the tropical and subtropi cal gyres: It is estimated that 6% of the northward salt transport in the Pacific at 8 degrees N is accomplished by the southward flow of fr esh intermediate water in the Mindanao Current. This transport is sens itive to fluctuations in the basin-scale wind forcing and is highly va riable;