Millennial and suborbital-scale El Niño/Southern Oscillation control of climate variability in southern China over the past 70 ka

Abstract

Hydroclimatic changes in East Asia on suborbital and millennial time scales have been shown to be highly uncertain. The El Niño-Southern Oscillation (ENSO) activity plays a key role in precipitation in low-latitude East Asia on interannual and interdecadal time scales. However, there remained some ambiguity about their connection on millennial and suborbital time scales. This study comprehensively explored the multifaceted relationships between ENSO activities, suborbital and millennial-scale drought events, and hydroclimatic variations within the Huguangyan Maar Lake (HML) region during the past 70 ka. Four suborbital-scale dry and wet hydroclimatic phases interspersed with ten millennial-scale extreme dry intervals were revealed by the ratio of hematite and goethite (Hem/Goe). These stages and intervals unexpectedly coupled with the zonal sea surface temperature (ΔSST) of the tropical Pacific Ocean, underscored the complex spatial and temporal dynamics of ENSO impacts. We propose the “glacial-El Niño-arid” and “interglacial-La Niña-humid” hydroclimate patterns on the suborbital scale. While on the millennial-scale, La Niña-like fluctuations during the persistent cold period (16–40 ka) increased the frequency and intensity of droughts in low-latitude East Asia, which was in stark contrast to the wet climate in northern China. The dynamic relationship underpins a millennia-spanning La Niña-drought pattern, elucidating the intertwined nature of ENSO dynamics and hydroclimatic variability on both sub-orbital and millennial scales. The above findings can be attributed to changes in the location and intensity of the Western Pacific subtropical high (WPSH) over southern China induced by persistent mean ENSO-like states in the tropical Pacific. This also indicates that the hydroclimate in low-latitude East Asia is more sensitive to variations in tropical ENSO compared to northern China.