NOAA/WDS Paleoclimatology - Padang Bai, Indonesia 20th Century Coral 14C Data

We have explored surface water mixing in the Lombok Strait through a bimonthly resolved surface water D14C time series reconstructed from a coral in the Lombok Strait that spans 1937 through 1990. The prebomb surface water D14C average is -60.5%, and individual samples range from -72% to 134%. The annual average postbomb maximum occurs in 1973 at 122%. The timing of the postbomb maximum is consistent with a primary subtropical source for the surface waters in the Indonesian seas. During the postbomb period, the coral records regular seasonal cycles of 5% to 20%. Seasonal high D14C occur during March-May (warm, low salinity), and low D14C occur in September (cool, higher salinity). The D14C seasonality is coherent and in phase with the seasonal D14C cycle observed in Makassar Strait. We estimate the influence of high D14C Makassar Strait (North Pacific) water flowing through the Lombok Strait using a two end-member mixing model and the seasonal extremes observed at the two sites. The percentage of Makassar Strait water varies between 16% and 70%, and between 1955 and 1990, it averages at 40%. The rich D14C variability has a biennial component reflecting remote equatorial Indian Ocean forcing and a component in the ENSO band, which is interpreted to reflect Pacific forcing on the D14C signature in Lombok Strait.