Holocene millennial climate variability influenced by tropical–Antarctic ocean–atmosphere interactions

A prominent unstable feature, millennial-scale climate oscillation (MCO), punctuated the Holocene. Solar activity and deep ocean variability are generally regarded as the origin of the MCO, yet the dynamics remain debated. Using a Holocene transient simulation with the EC-Earth climate model (8 to 0 ka BP), together with a global compilation of 304 temperature reconstructions, here we identify a robust ~1,350-y oscillatory mode that characterizes Holocene climate variability and is self-sustained and crucially influenced by tropical-Antarctic ocean-atmosphere interactions. Within each cycle, Antarctic Bottom Water (AABW) strengthening evolves with the developing warming and an El Niño-like tropical sea surface temperature (SST) response, accompanied by anticyclonic circulation anomalies over the high-latitude Southern Ocean. Northward cold advection of the associated enhanced westerly winds off the Antarctic coast overcomes the effect of sea ice retreat to promote AABW formation, ocean stratification, and warming. Positive feedbacks including sea ice-albedo, tropical air-sea interaction, and SST-AABW magnify surface warming till AABW reaches its peak. Thereafter, reduced brine rejection from sea-ice retreat weakens AABW, counteracts the warming, and commences a switch to its cooling phase. The dominant periodicity, consistent with that inferred from proxy reconstructions, is confirmed by complementary climate simulations. These results provide an alternative physical mechanism for Holocene millennial-scale climate variability. Under future anthropogenic warming, a positive phase of the oscillation may heighten the positive feedbacks, thereby increasing the risk of rapid climate transformation.