VENTILATION AND TRANSPORT OF THERMOCLINE AND INTERMEDIATE WATERS IN THE NORTHEAST PACIFIC DURING RECENT EL-NINOS

We present time series of tritium (H-3) concentrations in seawater fro m stations in the eastern subpolar (50-degrees-N, 145-degrees-W) and s ubtropical (28-degrees-N, 122-degrees-W) North Pacific. In the eastern subpolar North Pacific the tritium gradient between surface water and North Pacific Intermediate Water is smallest during years that coinci de with El Nino events. In the eastern subtropical North Pacific betwe en 200 and 400 m the tritium signature suggests that the water is of s ubpolar origin during non-El Nino years. During El Nino years, the wat er at this location is devoid of tritium. We hypothesize that the El N ino phenomenon alters both the ventilation of thermocline and intermed iate waters in the eastern subpolar North Pacific, as well as the tran sport of this water to the eastern subtropical gyre. Combined with sat ellite altimeter data, these results offer both a mechanism and a time frame by which subpolar water ventilates the vast reservoir of the su btropical North Pacific.