Relationship between the East Asian Summer and Winter Monsoons at Obliquity Time Scales

The relationship between the East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM) across time scales has been an interesting topic for decades. In this study, we quantitatively investigate the EASM-EAWM relationship at the obliquity time scales using a set of accelerated transient simulations. By comparing different indices defned with different variables, we fnd that the EASM and EAWM intensities are positively correlated under obliquity forcing. High obliquity leads to warmer summertime and cooler wintertime surface temperatures, with a stronger response observed over land than over the oceans. The warmer summertime and cooler wintertime temperature responses are accompanied by a strengthened Asian low in summer and Siberian high in winter, with enhanced southerlies in summer and northerlies in winter, indicating an enhanced EASM and EAWM. Modulated by ice sheet forcing, however, the evolution of the simulated EAWM shifts toward the ice sheet maximum, such that the circulation-based EASM-EAWM rela-tionship in the realistically forced simulation exhibits a phase shift of approximately 11 kyr, closer to the phase between the com-posite d18O and loess grain size in observations. Our results may have implications for better understanding the distinct changes in the proxy-based EASM-EAWM relationship before and after the rapid growth of global ice volume at around 3 Ma.