Holocene volcanic activity shaped centennial-scale variability of Northern Hemisphere land monsoon rainfall

Understanding the long-term evolution and variability of the Northern Hemisphere land monsoon rainfall (NHLMR) is crucial for interpreting past hydroclimate changes and assessing future monsoon responses. In this study, Holocene transient simulations are conducted to investigate the centennial-scale variability of NHLMR during the Holocene. Results show that on the orbital timescale, NHLMR closely follows Northern Hemisphere (NH) summer insolation, with a pronounced early-Holocene maximum followed by a gradual decline. Superimposed on this trend, volcanic activity exerts a strong influence on centennial-scale variability. A robust ∼120-year cycle appears in both the NHLMR and volcanic forcing. Volcanic eruptions cool the NH, weaken the cross-equatorial flow circulation, and reduce moisture transport, leading to almost coherent rainfall reductions across NH land monsoon regions. Volcanic forcing also induces a centennial-scale variability in a mega-ENSO-like pattern, which subsequently impacts the NHLMR. These findings demonstrate that volcanic forcing shaped centennial-scale variability on NHLMR, highlighting its key role in shaping past and potentially future monsoon behavior. 理解北半球陆地季风降水(NHLMR)的百年尺度变率对解读过去及未来气候变化至关重要.本研究基于包含火山强迫的全新世瞬变模拟试验, 发现火山活动是驱动NHLMR百年尺度变率的核心因子.火山喷发通过影响南北半球温度梯度, 并诱发百年尺度类巨型厄尔尼诺(mega-ENSO)来影响NHLMR, 造成几乎整个北半球陆地季风区一致偏干.本研究将火山强迫对季风系统的影响由年际,年代际尺度拓展至百年尺度, 为深入理解火山的气候效应及未来季风演变提供了更广阔的科学视角.