The early last glacial termination was characterized by intense North Atlantic cooling and weak overturning circulation. This interval between ~18,000 and 14,600 years ago, known as Heinrich Stadial 1, was accompanied by a disruption of global climate and has been suggested as a key factor for the termination. However, the response of interannual climate variability in the tropical Pacific (El Niño-Southern Oscillation) to Heinrich Stadial 1 is poorly understood. Here we use Sr/Ca in a fossil Tahiti coral to reconstruct tropical South Pacific sea surface temperature around 15,000 years ago at monthly resolution. Unlike today, interannual South Pacific sea surface temperature variability at typical El Niño-Southern Oscillation periods was pronounced at Tahiti. Our results indicate that the El Niño-Southern Oscillation was active during Heinrich Stadial 1, consistent with climate model simulations of enhanced El Niño-Southern Oscillation variability at that time. Furthermore, a greater El Niño-Southern Oscillation influence in the South Pacific during Heinrich Stadial 1 is suggested, resulting from a southward expansion or shift of El Niño-Southern Oscillation sea surface temperature anomalies.

Heinrich Stadial 1 Porites coral: 310-M0024A-11R-2, 1-62 cm; Fossil coral / U/Th-Age: 14.994 (+/-0.025) kyr before present (kyr BP; "present" is defined as AD 1950), Time period: 22 years around 15.0 kyr BP / Internal chronology starts at base (oldest part) of coral.

Supplement to: Felis, Thomas; Merkel, Ute; Asami, Ryuji; Deschamps, Pierre; Hathorne, Ed C; Kölling, Martin; Bard, Edouard; Cabioch, Guy; Durand, Nicolas; Prange, Matthias; Schulz, Michael; Cahyarini, Sri Yudawati; Pfeiffer, Miriam (2012): Pronounced interannual variability in tropical South Pacific temperatures during Heinrich Stadial 1. Nature Communications, 3, 965