A multicentennial mode of North Atlantic climate variability throughout the Last Glacial Maximum

Paleoclimate proxy records from the North Atlantic region reveal substantially greater multicentennial temperature variability during the Last Glacial Maximum (LGM) compared to the current interglacial. As there was no obvious change in external forcing, causes for the increased variability remain unknown. Exploiting LGM simulations with a comprehensive coupled climate model along with high-resolution proxy records, we introduce an oscillatory mode of multicentennial variability, which is associated with moderate variations in the Atlantic meridional overturning circulation and depends on the large-scale salinity distribution. This self-sustained mode is amplified by sea-ice feedbacks and induces maximum surface temperature variability in the subpolar North Atlantic region. Characterized by a distinct climatic imprint and different dynamics, the multicentennial oscillation has to be distinguished from Dansgaard-Oeschger variability and emerges only under full LGM climate forcing. The potential of multicentennial modes of variability to emerge or disappear in response to changing climate forcing may have implications for future climate change.

Automated summary

Paleoclimate proxy records from the North Atlantic region show that temperature variability during the Last Glacial Maximum (LGM) was significantly higher than the current interglacial period. The causes for this increased variability remain unknown. Using simulations and proxy records, researchers have identified an oscillatory mode of multicentennial variability associated with the Atlantic meridional overturning circulation and salinity distribution. This self-sustained mode, amplified by sea-ice feedbacks, induces maximum surface temperature variability in the subpolar North Atlantic region. This multicentennial oscillation is distinct from Dansgaard-Oeschger variability and only emerges under full LGM climate forcing. The potential for multicentennial modes of variability to respond to changing climate forcing may have implications for future climate change.