Robust expression of ENSO throughout the Last Interglacial

The El Niño-Southern Oscillation (ENSO) is a driver of global atmosphere-ocean dynamics, but projections of frequency and magnitude in different climate states remain uncertain. Palaeoclimate records offer the potential to improve our understanding of ENSO behaviour but most are fragmentary, suffer low resolution, and/or typically do not cover periods warmer than present day. The Last Interglacial (129-116 kyr BP) was the most recent period during which global temperatures were close to 21st century projections, and potentially provides insights into operation of climate modes of variability in the future. Here we report a continuous, inter-annually resolved record of hydroclimate spanning 220-80 ka from Lynch’s Crater in tropical northeast Australia, a region highly sensitive to ENSO. Our reconstruction is based on a micro-X-ray fluorescence (XRF)-generated elemental profile at 200 µm resolution, combined with loss-on-ignition, magnetic susceptibility, and pollen analysis. We find that during globally warmer periods (including super-interglacial Stage 5e, and 5c), there are significantly larger amplitudes in high-frequency ENSO spectral range (3-8 years), which are absent from the record during the glacial stages MIS6 and MIS4. Our results imply an ENSO dependence on mean climate, with enhanced ENSO variance during interglacials globally warmer than present. These results are consistent with climate model projections for a future slowdown of the Walker circulation and more extreme El Niño events under greenhouse warming.