SEA-LEVEL RESPONSE TO THE 1986-1987 EL-NINO SOUTHERN OSCILLATION EVENT IN THE WESTERN PACIFIC IN THE VICINITY OF PAPUA-NEW-GUINEA

Sea levels at the Papua New Guinea coast responded to the 1986-87 El N ino-Southern Oscillation (ENSO) event much as would be expected for po ints on the inshore edge of a western boundary current driven by remot e sea level disturbances. The first empirical orthogonal function of s ea level in the region accounts for 60% of the variance, and shows a c lear western boundary current signal. Sea level observations from tide gauges and estimates from adjacent expendable bathythermographs (XBTs ) am in good agreement, so XBT data are used to supplement sea level r esults; specifically, we obtain an estimate of the western boundary cu rrent as a function of depth. The anomalous transport through Vitiaz S trait varied by about 15 Sv during the event, with possibly more follo wing the eastern New Ireland coast. The western boundary current respo nse appears to be located entirely equatorward of the inflow feeding i t, as expected from linear theory. The boundary current followed the T robriand Island ridge, rather than the main Papua New Guinea coastline , and appears to bifurcate along southern New Britain. A maximum respo nse to the ENSO occurred south of New Ireland, where steric sea level appeared to vary by up to 45 cm due to the ENSO event; this may be an inertial feature.