Spatial differences in East Asian climate transition at ∼260 ka and their links to ENSO

The East Asian summer precipitation exhibits significant spatial differences from inter-annual to sub-orbital timescales, which has been associated with El Niño-Southern Oscillation (ENSO). However, studies on spatial patterns of climate and their mechanisms on orbital and tectonic timescales are still scarce, impeding a better understanding of Asian monsoon dynamics on long timescales. Here, we present a loess section spanning the past 430 ka in the Menyuan (MY) basin from the Northeastern Tibetan Plateau (NETP), and compare it with records from other sites in East Asia in order to explore the spatial patterns of climate changes and their mechanisms. Our results reveal a distinct climate transition at ∼260 ka in various records, which is characterized a transition from a “wet–dry–wet” to a “dry–wet–dry” pattern in the north-south direction and a transition from a “dry–wet” to “wet–dry” pattern in the west-east direction. This climate transition coincides with a significant weakening of the equatorial Pacific zonal (east–west) thermal gradient which indicates a shift to a more El Niño-like state, suggesting that the climate transition in East Asia at ∼260 ka could be related to paleo-ENSO variation. A more El Niño-like state could force an intensification and southwestward extension of the Western Pacific Subtropical High (WPSH) which could in turn move the rainfall front westward with the maximum rainfall belt over central China, resulting in the persistence of the observed climate patterns in East Asia. Our model results suggest that the change of the paleo-ENSO condition at ∼260 ka could be related to the eccentricity-modulated insolation and the ice shelve changes in northern high latitudes . Our study highlights the important role of paleo-ENSO in regulating the long-term climate changes in different sub-regions in East Asia. • The East Asian monsoon region is divided into four sub-regions. • A transition of meridional tripole climate pattern in East Asia occurred at ∼260 ka. • A transition of zonal dipole climate pattern existed in mid-latitude monsoonal region. • Paleo-ENSO was the dominant forcing for the ∼260 ka climate transition. • Paleo-ENSO may be influenced by changes in eccentricity and Arctic ice shelves.