Cross‐equatorial tracer transport in the upper waters of the Pacific Ocean

Abstract

Tritium samples have been analyzed from several cross‐equatorial transects in the Pacific under the NORPAX and EPOCS programs. Together with earlier sections from the GEOSECS program, they allow description of the equatorial Pacific tritium transient over a period extending between approximately the tenth and the fifteenth year after the major nuclear tests. South of the equator within the upper water layers at temperatures above 16°, an increase of 25–60% in the decay‐corrected tritium concentration is found. A northern hemisphere source for the tritium increase is unequivocally indicated, but the details of the exchange are as yet uncertain. The tritium transient evolution is consistent with recent suggestions that the net cross‐equatorial oceanic heat transport in the Pacific is small on the scale of the global atmospheric heat transport processes. An additional result relevant to the equatorial heat budget is that the tritium data put a lower bound of 16° on the temperature of the water up welling at the equator.