梵净山世界自然遗产地全新世以来的古气候变化

全新世是距离人类最近的间冰期,其气候变化受到广大学者的关注。中国东亚季风区全新世以来的气候变化对于揭示全球气候变化的驱动机制、预测未来气候变化具有重要意义。本研究通过对地处西南季风与东南季风过渡区的贵州梵净山世界自然遗产地九龙池湿地冰蚀湖相沉积JL15柱芯样品剖面孢粉、烧失量、碳氮含量的分析,结合加速器质谱(AMS)14C测年结果,建立了该地区全新世以来的古环境演变序列。结果表明,梵净山地区全新世以来经历了冷干期、过渡期、暖湿期、暖干期和冷干期5个阶段,其中第Ⅲ阶段(8. 0～4. 6 cal ka BP)可能为全新世大暖期的鼎盛期。总体而言,全新世早中期由干冷转为暖湿,后期气候逐渐转为寒冷干燥,但存在变暖的趋势。JL15柱芯共记录了全新世以来5次较明显的降温事件:2. 6、3. 4、4. 2、9. 4和10. 0 cal ka BP,其中与北大西洋浮冰碎屑(IRD)事件有联系的是4. 2和9. 4 ka事件。与西南地区其他气候记录相似,梵净山JL15柱芯所反映的冷事件与IRD事件存在一定联系,但也存在差异性,这可能与全球气候变化驱动机制的复杂性有关,需要后续研究的进一步探讨。

Paleoclimate Change of the Fanjingshan World Natural Heritage Property since Holocene

Holocene is the latest interglacial period to mankind, and the climate change during this period has attracted attentions of many scholars. The climate change since Holocene in the east Asian monsoon region of China has played an important role in revealing driving mechanisms of the global climate change and predicting the future change. By analyzing data of pollen, loss on ignition, the contents of organic carbon and nitrogen from Core JL15 of a sedimentary tarn, Jiulongchi Wetland, in the Fanjingshan World Natural Heritage property, which located in the transition zone of southwest monsoon and southeastern monsoon, and based on ¹⁴C dating results of Accelerator Mass Spectrometry (AMS), Holocene paleoenvironment evolution processes in this area were established. The results showed that since Holocene, Fanjingshan had experienced five climate change stages, cool-dry period, transition period, warm-wet period, warm-dry period and cool-dry period. Among these periods, the stage III (8.0-4.6 cal ka BP) was the warmest period of the Holocene Thermal Maximum. Overall, during early and middle Holocene, climate changed from cool-dry to warm-wet, however in late Holocene, it turned into cool-dry gradually. But there existed a trend of being warmer. The environmental proxies of Core JL15 had also recorded five relatively obvious cooling events since Holocene, occurring in 2.6, 3.4, 4.2, 9.4 and 10.0 cal ka BP. The 4.2 and 9.2 cooling events were relevant to the Ice-rafted debris (IRD) event in north Atlantic. Similar to other records of southwest China, the cooling events reflected by Core JL15 of Fanjingshan showed similar correlations with the IRD event. This may relate to the complexity of the driving mechanism of global climate change, which needs later discussion.