THE DISTRIBUTION OF INTERMEDIATE WATER IN THE WESTERN EQUATORIAL PACIFIC DURING JANUARY FEBRUARY 1986

The distribution of intermediate water in the western equatorial Pacif ic (WEP) for the two month period January-February, 1986, is examined with hydrographic data collected by researchers on six different ships from five different countries. The WEP contains intermediate waters d erived from the poleward reaches of both the North and South Pacific, and the mixing of these waters creates a complex and interleaving patt ern of fronts. Antarctic Intermediate Water (AAIW) enters the WEP via the Vitiaz Strait in the New Guinea Coastal Undercurrent with a charac teristic salinity minimum of about 34.55 at a density of approximately 27.2 sigma(theta). The salinity minimum is seen as far north as 10 de grees N; however, distributions of oxygen indicate that newer AAIW fro m the South Pacific spreads only as far as 2 degrees S to the east of 143 degrees E and possibly further north to the west of 143 degrees E. North Pacific Intermediate Water (NPIW) has a salinity minimum of les s than 34.5. It enters the WEP via the Mindanao Current at 26.5-26.6 s igma(theta) and spreads eastward in the North Equatorial Countercurren t (NECC) as a thin filament at about 2-3.5 degrees N. This filament is visible as far east as 150 degrees E. An intermediate water mass name d North Pacific Tropical Intermediate Water (NPTIW) is found between t wo fronts at approximately 4.5 and 10 degrees N between 26 and 27 sigm a(theta). NPTIW is associated with a core salinity maximum and oxygen minimum at 26.8 sigma(theta) and may be part of a ''shadow zone'', an area of weak flow isolated from surface forcing. A companion to NPTIW South Pacific Tropical Intermediate Water (SPTIW), spreads into the we stern equatorial Pacific in the Equatorial Intermediate Current along the Equator centred at 27.1 sigma(theta). It is identified by a latera l oxygen minimum between 2 degrees N and 2 degrees 5 as far west as 14 3 degrees E.