Upper-ocean-to-atmosphere radiocarbon offsets imply fast deglacial carbon dioxide release

At the end of the last ice age, rising atmospheric carbon dioxide levels coincided with a decline in carbon-14 levels, suggesting the release of very 'old' (radiocarbon-depleted) carbon dioxide from the deep ocean to the atmosphere. Rose et al. present radiocarbon records of surface and intermediate depth waters from two sediment cores in the southwest Pacific and Southern Ocean, and find a steady 170 per mil decrease in Δ14C that precedes and roughly equals in magnitude the decrease in the atmospheric radiocarbon signal during the early stages of the glacial–interglacial climatic transition. The initial rise in carbon dioxide levels may have originated from intermediate Southern Ocean water masses that were not strongly depleted in radiocarbon, followed by the release of radiocarbon-depleted carbon dioxide from deeper North Pacific waters.