Orbital‐Millennial Scale Hydroclimate Variations in the Mid‐Lower Yangtze River Valley During the Last Glacial: Insights From Stalagmite Multi‐Proxy Records

Abstract

Geological evidence shows that Heinrich Stadials (HS1–HS4) during the Last Glacial Period were associated with a weakened East Asian summer monsoon (EASM) linked to reduced Atlantic Meridional Overturning Circulation (AMOC). However, regional hydroclimate responses remain poorly constrained. Here, we present a multi‐proxy record from stalagmite YXG01 (47–12 ka BP) from Yindi Cave in the mid‐lower Yangtze River Valley. The stalagmite YXG01 δ ¹⁸ O record exhibits positive excursions during HSs, reflecting reduced EASM intensity. In contrast, synchronous negative shifts in δ ¹³ C and trace element ratios (Mg/Ca, Sr/Ca, and Ba/Ca), together with elevated initial δ ²³⁴ U values and enhanced growth rates, indicate enhanced local hydroclimatic conditions during these intervals. These contrasting signals suggest a decoupling between large‐scale monsoon intensity and regional hydroclimate, likely driven by southward displacement of the westerly jet and the western Pacific subtropical high (WPSH). Notably, this decoupling persists from millennial to orbital timescales. At the orbital scale, EASM intensity variations broadly follow Northern Hemisphere summer insolation (NHSI) but remains anti‐phased with local hydroclimate variations. Comparison with other records across eastern China reveals a coherent tripolar precipitation pattern—characterized by drier conditions in central‐eastern regions and wetter conditions in northern and southern regions during periods of strong summer insolation. This pattern likely reflects intensified atmospheric circulation and a northward shift of both the WPSH and the westerly jet, resulting in northward migration of the EASM rain belt. Robustly assessing this tripolar structure requires more high‐quality records to refine future hydroclimate projections under global warming.