Throughout the transition from the last Glacial to the current Interglacial, rising atmospheric CO2 levels were accompanied by declining atmospheric Δ¹⁴C values. A likely mechanism, influencing both records is the deglacial release of CO₂, stored for millennia in the deep Ocean, to the atmosphere. Due to its long residence time within the oceans interior this CO₂ rich water mass was considerably depleted in radiocarbon. Although a large number of studies address this topic, the extent, location and pathways of the glacial carbon pool are still subjects of an ongoing debate. As deep water masses are upwelled and new intermediate waters are formed around Antarctica, the Southern Ocean is a potential area for the deglacial release of stored CO₂. We use radiocarbon reconstructions from a transect of sediment cores off New Zealand and the central South Pacific that covers the major water masses in this area, from the Antarctic Intermediate Water down to the Antarctic Bottom Water. During the Glacial, our data locate a significantly ¹⁴C-depleted and CO₂-enriched pool in the South Pacific below ~2000 m water depth.

Thomas Ronge

Scheme of the glacial carbon pool. During the glacial, deep water masses were separated from the surfaces and could accumulate large quantities of CO₂ (dark blue shading). Separated from the old carbon pool by a pronounced chemocline (red line), better ventilated Antarctic Intermediate Waters (AAIW) are indicated by the light blue shading. ©Thomas Ronge/AWI