HR: 11:50h
AN: PP21D-07    [PDF]
TI: SPCZ- and ENSO-related Salinity Variations Recorded in the Skeletal Geochemistry of a Porites Coral from Espiritu Santo, Vanuatu
AU: * Kilbourne, K H
EM: hali@marine.usf.edu
AF: University of South Florida, College of Marine Science, 140 7th Ave. South, St. Petersburg, FL 33701 United States
AU: Quinn, T M
EM: tquinn@marine.usf.edu
AF: University of South Florida, College of Marine Science, 140 7th Ave. South, St. Petersburg, FL 33701 United States
AU: Taylor, F W
EM: fred@utig.ig.utexas.edu
AF: Institute for Geophysics, The University of Texas at Austin, 4412 Spicewood Springs Rd, Austin, TX 78759-8500 United States
AU: Delcroix, T
EM: delcroix@notos.cst.cnes.fr
AF: D‚partement milieux et environnement, LEGOS, 18 Avenue Edouard Belin 31401 Toulouse cedex 4, Tolouse, 31401 France
AU: Gouriou, Y
EM: gouriou@ird.fr
AF: IRD de Noumea, BP A5, 98848 Noum‚a cedex, Noumea, 98848 New Caledonia
AB: Variations in sea surface temperature (SST) and sea surface salinity (SSS) are important components of climate variability in the tropical ocean-atmosphere system. Instrumental SST time series are much more readily available than are instrumental SSS time series, which are exceedingly rare. SSS variations are strongly linked to seawater $\delta^{18}$O variations in the tropics, thus coral-based reconstructions of seawater $\delta^{18}$O offer an opportunity to reconstruct the history of SSS variations in the tropical oceans. Seawater $\delta^{18}$O is obtained by combining coral skeletal $\delta^{18}$O, which varies in response to changes in seawater $\delta^{18}$O and SST, with coral skeletal Sr/Ca, which varies in response to SST changes. This method has great potential for reconstructing past salinity variations. We explore this potential using a monthly-resolved, 65-year record of skeletal $\delta^{18}$O and Sr/Ca variations in a Porites coral from Espiritu Santo, Vanuatu ($16.0\deg$S, $166.7\deg$E). Santo is well positioned for such a study because ENSO-related climate variability strongly influences local salinity through changes in the position of the center of South Pacific Convergence Zone (SPCZ) convection/precipitation and associated salinity front movements. Moreover, a 24-year record of SSS variations is available from this region, which permits a ground-truth assessment of the robustness of the coral-based seawater $\delta^{18}$O-SSS reconstruction. Investigation into different methods of combining coral $\delta^{18}$O and Sr/Ca to reconstruct SSS reveals that the coral $\delta^{18}$O anomaly time series provides the best fit to the SSS time series. A post-1976/1977 freshening trend in the $\delta^{18}$O anomaly time series, which has been documented in other proxy time series, increases our confidence that this time series accurately reflects changes in the hydrologic balance in the western tropical Pacific. The Vanuatu coral $\delta^{18}$O anomaly time series also correlates strongly with the Southern Oscillation Index, the Ni\~{n}o 3.4 SST anomaly time series, and with a SPCZ index derived from rainfall records. The results of this study confirm that coral geochemical records from Espiritu Santo, Vanuatu are climatically significant and that longer modern coral records and fossil coral records from this area contain a robust archive of past variability in SSS, SPCZ and ENSO.
DE: 3309 Climatology (1620)
DE: 3344 Paleoclimatology
DE: 4215 Climate and interannual variability (3309)
DE: 4267 Paleoceanography
DE: 4522 El Ni¤o
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting