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 suborbital timescales, which has been associated with El Nino-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 similar to 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 Nino-like state, suggesting that the climate transition in East Asia at similar to 260 ka could be related to paleo-ENSO variation. A more El Nino-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 similar to 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. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

The spatial patterns of climate changes in East Asia on orbital and tectonic timescales and their mechanisms are still poorly understood. In this study, a loess section from the Northeastern Tibetan Plateau spanning the past 430 ka is compared with records from other sites in East Asia to explore the spatial patterns of climate changes and their mechanisms. The results suggest a climate transition at around 260 ka, coinciding with a weakening of the equatorial Pacific zonal thermal gradient and a shift to a more El Nino-like state, which could explain the observed climate patterns in East Asia.