Deglacial sea-level record from Tahiti corals and the timing of global meltwater discharge

Abstract

THE timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets¹ and their effects on the Earth's surface^2,3. Moreover, the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans, which probably disturbed the ocean's thermohaline circulation and, hence, global climate^4–7. Sea-level increases bear witness to the melting of continental ice sheets, but only two such records—from Barbados^8,9 and New Guinea^10,11 corals—have been accurately dated. But these corals overlie active subduction zones, where tectonic movements are large and often discontinuous (especially in New Guinea), so the apparent sea-level records may be contaminated by a complex tectonic component. Here we date fossil corals from Tahiti, which is far from plate boundaries (and thus is likely to be tectonically relatively stable) and remote from the locations of large former ice sheets. The resulting record indicates a large sea-level jump shortly before 13,800 calendar years BP, which corresponds to meltwater pulse 1A in the Barbados coral records^8,9. The timing of this event is more accurately constrained in the Tahiti record, revealing that the meltwater pulse coincides with a short and intense climate cooling event^12–15 that followed the initiation of the Bølling–Allerød warm period^12–16, but preceded the Younger Dryas cold event by about 1,000 years.