Distinct responses of East Asian summer and winter monsoons to astronomical forcing

Abstract

Influences of the Earth's astronomical forcing on the evolution of East Asian monsoon have been demonstrated with various geological records and climate models. Here, we present time series of climatic proxies from the Chinese Loess Plateau and Sanbao/Hulu caves and the winter/summer monsoon intensity index from a long-term transient climate model simulation. Both the observations and modelling results reveal consistently distinct responses of East Asian summer and winter monsoons to astronomical forcing. Different from the dominant local impact on the summer monsoon at the precession scale (~20 ka period), the East Asian winter monsoon is driven predominantly by the obliquity forcing (~40 ka period). We propose that the obliquity forcing controls the meridional insolation difference and, therefore, exerts a more significant effect on the evolution of the East Asian winter monsoon than previously expected.