AMOC Modulates Ocean Heat Content During Deglaciations

Abstract

During deglaciations, Earth takes up vast amounts of energy, about half of which heats the global ocean. Thus, ocean heat content (OHC) is a key metric to assess Earth's energy budget. Recent modeling studies suggest that OHC changes not only in response to orbitally driven climate change but is also modulated on millennial timescales by the Atlantic Meridional Overturning Circulation (AMOC). Here, we present the first OHC record for the last four deglaciations using noble-gas ratios in the EPICA Dome C ice core. The record reveals millennial-scale OHC variability in all studied deglaciations, most prominently as OHC maxima at the end of Terminations II, III, and IV. These millennial-scale OHC changes are anti-correlated with AMOC strength, suggesting that the AMOC modulates OHC across different climate states. Furthermore, given the magnitude of the end-of-termination OHC maxima, AMOC-induced OHC changes may be an important control of early interglacial atmospheric CO₂, sea level, and climate.