Multidecadal variability of Northern Hemisphere land monsoon precipitation dominated by explosive volcanic eruptions over the last millennium

Volcanic eruptions are among the most profound sources of natural external radiative forcing of the climate system, imparting significant impacts on global and regional climate. Previous studies have established that explosive volcanic forcing induced substantial multidecadal (∼50–70-year timescale) variability in global mean temperature during the last millennium. The consequences for other climate subsystems remain largely unexplored. In this study, volcanic forcing-induced multidecadal variability of the Northern Hemisphere land monsoon (NHLM) and sub-monsoon precipitation is examined through comparison between climate model simulations and speleothem δ 18 O climate proxy records. We find that volcanic forcing plays a long-term role in modulating the NHLM system and associated precipitation on multidecadal timescales. This variability, however, is consistently found in both proxy records and model simulations, to be intermittent. Volcanic-induced multidecadal variability is observed in the North African monsoon region between 1150 and 1300, while the South Asian monsoon is strongly influenced between 1750 and 1850. In contrast, the East Asian monsoon precipitation exhibits multidecadal variability not directly caused by volcanic eruptions, and the America monsoon region shows no clear volcanic response. These differences can be attributed to the nonlinear, threshold-based responses of sub-monsoon systems to volcanically induced radiative forcing, with responses to weaker forcing indistinguishable from internal variability. Our findings highlight the important, but somewhat complex, linkage between natural volcanic radiative forcing and the response of certain subsystems, such as the NHLM and associated precipitation, to that forcing. 基于气候模式与石笋δ18O记录的对比, 分析了过去千年强火山对北半球陆地季风 (NHLM) 及其子季风区降水多年代际 (约40–60年) 变率的调制作用.结果表明, 火山强迫主导了NHLM降水多年代际变率, 但影响呈现间歇特点和区域差异:1150–1300年北非季风区响应强烈, 1750–1850年南亚季风区受控明显;东亚季风降水非完全由火山直接影响所致, 美洲季风区无明确火山信号.原因在于:子季风区对火山响应为非线性, 部分区域强内部变率可掩盖火山信号, 且不同区域响应模式各异.本研究揭示了强火山喷发与陆地季风降水之间的复杂关联.