Radiocarbon constraints on the extent and evolution of the South Pacific glacial carbon pool

During the last deglaciation, the opposing patterns of atmospheric CO 2 and radiocarbon activities (Δ 14 C) suggest the release of 14 C-depleted CO 2 from old carbon reservoirs. Although evidences point to the deep Pacific as a major reservoir of this 14 C-depleted carbon, its extent and evolution still need to be constrained. Here we use sediment cores retrieved along a South Pacific transect to reconstruct the spatio-temporal evolution of Δ 14 C over the last 30,000 years. In ∼2,500–3,600 m water depth, we find 14 C-depleted deep waters with a maximum glacial offset to atmospheric 14 C (ΔΔ 14 C=−1,000‰). Using a box model, we test the hypothesis that these low values might have been caused by an interaction of aging and hydrothermal CO 2 influx. We observe a rejuvenation of circumpolar deep waters synchronous and potentially contributing to the initial deglacial rise in atmospheric CO 2 . These findings constrain parts of the glacial carbon pool to the deep South Pacific.