Surface Water Mixing in the Solomon Sea as Documented by a High-Resolution Coral 14C Record

A bimonthly coral-based record of the postbomb radiocarbon content of Solomon Sea surface waters is interpreted to reflect mixing of subtropical surface water and that advected in from the east by the equatorial branch of the South Equatorial Current (SEC). Annual mean D14C has a dynamic range of nearly 175‰, with a total range of nearly 200‰. Prebomb values average 256‰ and the annual mean postbomb maxima occurs in 1985 with a value of 1117%. Interannual variability in the record reflects surface current variations in conjunction with surface wind changes associated with ENSO. During El Niño years the waters of the Solomon Sea reflect a stronger influence of waters advected in from the east by the SEC and less ‘‘pure’’ subtropical water. This is most likely accomplished by a southward shift of the equatorward branch of the SEC during El Niño. There is an overall decrease in the relative proportion of eastern tropical water that is interpreted as a decrease in the strength and intensity of the shallow circulation of the tropical Pacific during the latter portion of the twentieth century. If validated, this secular trend bears strongly upon the rate of extratropical–tropical recirculation and the redistribution of heat and salt within the tropical Pacific.