Temperature and Surface-Ocean Water Balance of the Mid-Holocene Tropical Western Pacific

Skeletal Sr/Ca and $^{18}$O/$^{16}$O ratios in corals from the Great Barrier Reef, Australia, indicate that the tropical ocean surface ∼5350 years ago was 1°C warmer and enriched in $^{18}$O by 0.5 per mil relative to modern seawater. The results suggest that the temperature increase enhanced the evaporative enrichment of $^{18}$O in seawater. Transport of part of the additional atmospheric water vapor to extratropical latitudes may have sustained the $^{18}$O/$^{16}$O anomaly. The reduced glacial-Holocene shift in seawater $^{18}$O/$^{16}$O ratio produced by the mid-Holocene $^{18}$O enrichment may help to reconcile the different temperature histories for the last deglaciation given by coral Sr/Ca thermometry and foraminiferal oxygen-isotope records.