Glacial water mass structure and rapid δ 18 O and δ 13 C changes during the last glacial termination in the Southwest Pacific

Abstract Changes in ocean circulation are thought to have contributed to lowering glacial atmospheric CO 2 levels by enhancing deep ocean sequestration of carbon that was returned to the atmosphere during glacial terminations. High-resolution benthic foraminiferal δ 13 C and δ 18 O records from a depth transect of cores in the Southwest Pacific Ocean presented here provide evidence that both wind- and thermohaline-driven circulation drove CO 2 from the ocean during the last deglaciation. Shallow geochemical stratification in the glacial Southern Ocean was followed by a short pulse of rapid δ 13 C enrichment to intermediate water depths during Heinrich Stadial 1, indicative of better-ventilated intermediate waters co-occurring with documented wind-driven upwelling in the Southern Ocean. Intermediate depth δ 13 C enrichment paused at the start of the Antarctic Cold Reversal (∼14.7 ka), implying a brief shallow restratification, while deeper layers were progressively flushed of δ 13 C-depleted and δ 18 O-enriched waters, likely caused by the increasing influence of deep waters sourced from the North Atlantic. The coincidence of atmospheric CO 2 increases with these geochemical shifts in both shallow and deep cores suggests that shifts in both atmospheric and oceanic circulation contributed to the deglacial rise of CO 2 .