Southern Ocean contribution to both steps in deglacial atmospheric CO₂ rise

The transfer of vast amounts of carbon from a deep oceanic reservoir to the atmosphere is considered to be a dominant driver of the deglacial rise in atmospheric CO₂. Paleoceanographic reconstructions reveal evidence for the existence of CO₂-rich waters in the mid to deep Southern Ocean. These water masses ventilate to the atmosphere south of the Polar Front, releasing CO₂ prior to the formation and subduction of intermediate-waters. Changes in the amount of CO₂ in the sea water directly affect the oceanic carbon chemistry system. Here we present B/Ca ratios, a proxy for delta carbonate ion concentrations Δ[CO₃^2-], and stable isotopes (δ¹³C) from benthic foraminifera from a sediment core bathed in Antarctic Intermediate Water (AAIW), offshore New Zealand in the Southwest Pacific. We find two transient intervals of rising [CO₃^2-] and δ¹³C that that are consistent with the release of CO₂ via the Southern Ocean. These intervals coincide with the two pulses in rising atmospheric CO₂ at ~ 17.5-14.3 ka and 12.9-11.1 ka. Our results lend support for the release of sequestered CO₂ from the deep ocean to surface and atmospheric reservoirs during the last deglaciation, although further work is required to pin down the detailed carbon transfer pathways.