Toward quantifying the deep Atlantic carbon storage increase during the last glaciation

Ice core records show that atmospheric CO₂ concentrations during peak glacial time were ~30% lower than the levels during interglacial periods. The terrestrial biosphere carbon stock was likely reduced during glacials. Increased carbon storage in the deep ocean is thought to play an important role in lowering glacial atmospheric CO₂. However, it has been challenging to quantify carbon storage changes in the deep ocean using existing proxy data. Here, we present deepwater carbonate ion reconstructions for a few locations in the deep Atlantic. These data allow us to estimate the minimum carbon storage increase in the deep Atlantic Ocean during the last glaciation. Our results show that, despite its relative small volume, the deep Atlantic Ocean may contribute significantly to atmospheric CO₂ variations at major climate transitions. Furthermore, our results suggest a strong coupling of ocean circulation and carbon cycle in the deep Atlantic during the last glaciation.