既往研究认为，受海因里希Ⅰ(Heinrich Stadial I，HS1 )早期（约18.3-16.3 ka B.P.）北半球降温的影响，热带辐合带（ITCZ）雨带的平均位置会向南移动。 但是，另一种观点认为， HS1早期（18.3-16.3 ka）热带降水在印太澳（IAA）季风区可能发生了经向收缩。可见，HS1早期ITCZ对北大西洋降温事件的响应方向及位移幅度仍存争议。孟加拉湾的海洋炭屑记录保存了北部陆地大量气候成因古火事件的信息。研究发现HS1早期（18.3-16.3ka），位于9.9°N的YDY09孔炭屑总浓度、木本炭屑百分比均降至最低，而草本炭屑百分比升高；结合有孔虫和石笋δ¹⁸O记录等指标记录的降水减少，指示火事件发生频率急剧减少，可能与当时气候干旱和温度降低引起的陆源区植被减少有关；与位于9.9°N的YDY10及孟加拉湾上扇的E87-32B常绿阔叶林低值反映的干旱情况一致，反映炭屑源区当时处于ITCZ雨带范围之外。说明炭屑与孢粉、有孔虫等其他指标重建的印度夏季风降水结果一致。同时，YDY09全新世中期火灾活动（尤其是草本炭屑）的急剧下降，与该孔的粪生真菌孢子百分比在4.5 ka以来急剧增加相对应，后者被认为是青藏高原南部、恒河平原和印度东部史前人类驯化动物的结果，暗示人为的放牧增加可能促使草本生物量减少，间接抑制了该区域的火灾强度。

Previous studies have suggested that the mean position of the tropical convergence zone (ITCZ) rain-belt shifted southward due to the cooling of the Northern Hemisphere during the Heinrich Stadial I (HS1) period (approximately 16.3 - 18.3 ka B.P.). However, an alternative perspective proposes that tropical precipitation in the Indo-Asian-Australian (IAA) monsoon region may have undergone a meridional contraction during the early HS1. It can be seen that the response and displacement amplitude of the ITCZ to the cooling event in the North Atlantic during HS1 remain controversial. Marine charcoal records from the Bay of Bengal may preserve critical information about climate-driven ancient fire events from the northern land. In this study, we find that the total concentration of charcoal and the percentage of woody charcoal in YDY09 core (located at 9.9°N) declined to the lowest levels in the Early HS1, while the percentage of herbaceous charcoal increased. This suggests a sharp reduction in the frequency of fire events, consistent with decreased rainfall inferred from the δ18O records of foraminifera and stalagmites, and other proxies. The decline in fire events may be related to reduced vegetation cover under drier climate and cooler climatic conditions，reflecting that the source area was outside the range of the ITCZ at that time. The change aligns with evidence of aridity from low pollen values of evergreen broad-leaved forest in YDY10 core (located at 9.9°N) and E87-32B core from the upper submarine fan of the Bay of Bengal. These findings support the coherence of Indian summer monsoon precipitation reconstructions using charcoal and other proxies. At the same time, the abrupt decline in fire activity in core YDY09 during the Holocene mid-period, especially the increase in herbaceous charcoal, corresponds to a sharp increase in the percentage of coprophilous fungal spore after 4.5 ka. The latter has been attributed to prehistoric human animal domestication on the southern Qinghai-Tibet Plateau, the Gangetic Plain, and eastern India. It implies that intensified grazing may have reduced herbaceous biomass, indirectly suppressing the fire intensity in this region.