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.