Decadal-scale hydroclimate variations in the eastern part of westerlies-dominated central Asia since the Little Ice Age

The decadal-scale climate change represents a critical feature of the Earth’s climate system. However, investigations into the decadal hydroclimate dynamics in the westerlies-dominated Central Asia—governed by the mid-latitude westerly circulation—remain incomplete, particularly concerning the mechanistic shifts in decadal hydroclimate patterns under global warming. Therefore, systematically resolving the decadal hydroclimate evolution in the past several centuries in this region is pivotal for deciphering regional climate responses and underlying drivers in the context of global warming. We synthesized 46 high-resolution geological records from tree rings, ice cores, lake sediments, and stalagmites, in the eastern part of the westerlies-dominated Central Asia. By integrating multi-taper method (MTM) analysis and complementary methodologies, we comprehensively characterized the spatiotemporal signatures and the driving mechanisms of decadal hydroclimate variations since the Little Ice Age. Our findings reveal that decadal hydroclimate during the Little Ice Age exhibited dual cyclicities of 10～35 years and 45～82 years, whereas the Current Warm Period was dominated by 10～35-year cycle. Pronounced spatial heterogeneities were observed across the regions, with a consistent warm-wetting trend in the Current Warm Period. The transition (1800—1920 AD) was marked by an overall decadal “drought-wet-drought” transition process, with the 1910s extreme drought event showed regional universality. The solar activity-modulated the North Atlantic Oscillation (NAO) phase shifts and meridional excursions of the mid-latitude westerlies played a pivotal role in the decadal variations of the regional hydroclimate, while volcanic activities modulated extreme events. The warm-wetting trend in the Current Warm Period reflects enhanced human influences. This research provided multi-proxy evidence for understanding climate response mechanisms of the Central Asian westerlies under global change. Future efforts shall integrate high-resolution geological archives with numerical simulations to quantify the contributions of natural versus anthropogenic factors to decadal hydroclimate dynamics.