EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

New insights of the East Asian summer monsoon variability over the past 800 kyr from a transient simulation with CLIMBER-2

Liya Jin1, Andrey Ganopolski2, Matteo Willeit2, Huayu Lu3, Fahu Chen4, and Xiaojian Zhang3
Liya Jin et al.
  • 1School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China (
  • 2Potsdam Institute for Climate Impact Research, Potsdam14412, Germany
  • 3Frontiers Science Center for Critical Earth Material Cycling, School of Geography and Ocean Science, Nanjing University, Nanjing 210023, China
  • 4Alpine Paleoecology and Human Adaption Group, Key Laboratory of Alpine Ecology, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China

The East Asian summer monsoon (EASM) is a major component of the global climate system with its variability closely associated with regional changes of rainfall, impacting the lives of over one sixth of the global population strongly. Understanding the periodicities of summer rainfall influenced by the EASM is beneficial to its future projections. However, the mechanism of the response of the EASM associated summer rainfall fluctuations to orbital-scale forcing during the late Pleistocene remains far from being well understood. Here, we provide an 800-kyr long series of EASM rainfall variations by extracting data from multiple transient simulations of CLIMBER-2 over the past 3 million years. Despite a coarse model resolution, the CLIMBER-2 captures a realistic spatial distribution and magnitude of present-day summer (June-July-August) rainfall, especially in East Asia. The CLIMBER-2 model simulates correct magnitude and timing of the last eight glacial cycles in respect to both global ice sheet volume (expressed in δ18O) and CO2 concentration. Both the simulation and reconstructions reveal predominant 100-ky and 41-ky cycles of global ice sheet volume and CO2 concentration, although precession (23- and 19-kyr) bands dominate high-latitude summer insolation. The EASM intensity is traditionally measured by the monsoonal circulation, i.e. the low-level southerly winds in summer over East Asia. Cross-spectral analysis confirms high coherence between model and proxy at 19-kyr and 41-kyr bands implying a strong low-latitude process modulated by precession. Unlike the EASM circulation from the CLIMBER-2, simulated boreal summer rainfall in East Asia, denoted as “EASM rainfall” shows pronounced 41- and 100-kyr cycles, resembling the loess record over the past 800 kyr. The simulation results reveal a decoupling between EASM rainfall and EASM circulation, which probably is a reasonable explanation for the conflicts in proxy records, and also reflects complicated mechanisms of the EASM system on glacial–interglacial timescales.

How to cite: Jin, L., Ganopolski, A., Willeit, M., Lu, H., Chen, F., and Zhang, X.: New insights of the East Asian summer monsoon variability over the past 800 kyr from a transient simulation with CLIMBER-2, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4963,, 2023.