New study reveals the role of subtle changes of Northern Westerlies in the East Asian monsoon variability

The new research titled "Interstadial diversity of East Asian summer monsoon linked to changes of the Northern Westerlies", published in Nature Communications at 10 am, August 25, 2025 (London time) (https://www.doi.org/10.1038/s41467-025-63057-2) and led by scientists from Xi’an Jiaotong University in China the British Antarctic Survey and international collaborators, shows that isotopic signatures of the EASM during DO events are not uniform but rather reflect diverse changes in response to subtle variations of the Westerlies’ position. “Our isotope-enabled climate model successfully replicates the spatial heterogeneity seen in proxy records, particularly the subdued δ18O depletion in Southeast China during short interstadials. This consistency validates the model’s ability to capture the Westerlies’ influence on EASM moisture transport, deepening our understanding of these dynamic processes”, said Xu Zhang, a climate modeler at the British Antarctic Survey.

The research bridges gaps in our understanding of how abrupt glacial climate events shape the regional hydroclimates. By analyzing high-resolution speleothem records from China and India alongside isotope-enabled climate model, the team found that short interstadials (brief warming phases) trigger further northward leap of the Westerlies relative to long interstadials. This leap facilitates the transport of near-source moisture from the western Pacific into East Asia, thereby suppressing the δ18O depletion seen in the short events. “Our findings complement the conventional view that the Westerlies’ shifts are simply binary—northward during all interstadials and southward during stadials,” said Xiyu Dong, a researcher at Xi’an Jiaotong University and the paper's first author, “instead, we observed a continuum of responses associated with the intensity of high-latitude warming. This nuanced behavior underscores the complexity of atmospheric dynamics behind abrupt climate changes.” The study further reveals that southeast China is a key region for investigating the interactions between the East Asian Summer Monsoon and the Westerlies during millennial-to-centennial-scale events, while India and Southwest China are critical for studying the tropical direct response to the Atlantic Meridional Overturning Circulation (AMOC).

“The robust geochronology from this study provides a number of important chronological benchmarks that allow us to refine part of the Greenland ice-core chronology. Furthermore, by synchronizing these records, we elucidate the role of AMOC in driving both short and long DO events”, said senior author Hai Cheng of Xi'an Jiaotong University. “Southeast China is a critical region for understanding the monsoon variability, yet it remains understudied due to the limited number of high-resolution proxy records, so more paleoclimate data from this region are needed to refine predictions of future hydroclimate changes”, said co-author Haiwei Zhang of Xi’an Jiaotong University.   

Looking Ahead

The authors call for more reconstructions of high-resolution paleoclimate records across East Asia to test their proposed mechanisms. “Deciphering past climate nuances,” Xu Zhang adds, “is crucial for unraveling the monsoon’s future in a warming world”.

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