德国森肯博哥生物多样性和气候研究中心Meijer, Niels团队近日的研究揭示，中亚的原始季风降雨和绿化归咎于始新世早期的极端变暖。相关论文于2024年1月29日发表于国际顶尖学术期刊《自然—地球科学》杂志上。
研究人员利用孢粉学和同位素记录，作为极端大气二氧化碳情景的模拟，来追踪整个温暖的始新世早期(5700万至4400万年前)的植被和湿度。研究结果显示，降雨量暂时增加了一倍，森林生态系统取代了区域草原。研究通过重建成土的碳酸盐生长的季节，限制其土壤水文状况，表明大部分降雨发生在夏季。因此，这一潮湿事件被归因于古新世—始新世极热期大量温室气体释放后，季风水汽的内陆扩张的结果，同时碳同位素的负偏移也证实了这一点。
由此导致的中亚草原-沙漠的突然绿化可能使哺乳动物得以扩散，并可能通过增强土壤有机碳埋藏和硅酸盐风化作用，在碳循环反馈中发挥作用。这些极端始新世的原始季风，虽然不同于今天由地形驱动的亚洲季风，但凸显了在未来全球变暖情况下，中亚降雨和生态系统可能会发生突变。
据了解，亚洲干燥的大陆内部在其地质历史的大部分时间里，一直保持干旱，然而，这一独特生态系统的未来仍不明确。
附：英文原文
Title: Proto-monsoon rainfall and greening in Central Asia due to extreme early Eocene warmth
Author: Meijer, Niels, Licht, Alexis, Woutersen, Amber, Hoorn, Carina, Robin-Champigneul, Faez, Rohrmann, Alexander, Tagliavento, Mattia, Brugger, Julia, Kelemen, Fanni D., Schauer, Andrew J., Hren, Micheal T., Sun, Aijun, Fiebig, Jens, Mulch, Andreas, Dupont-Nivet, Guillaume
Issue&Volume: 2024-01-29
Abstract: The dry continental interior of Asia has remained arid throughout most of its geological history, yet the future of this unique ecosystem remains unclear. Here we use palynological and isotopic records to track vegetation and moisture throughout the warm early Eocene (57 to 44 million years ago) as an analogue for extreme atmospheric CO2 scenarios. We show that rainfall temporarily doubled and replaced the regional steppe by forested ecosystems. By reconstructing the season of pedogenic carbonate growth, we constrain the soil hydrologic regime and show that most of this rainfall occurred during the summer season. This humid event is therefore attributed to an inland expansion of monsoonal moisture following the massive greenhouse gas release of the Palaeocene–Eocene Thermal Maximum as identified by a negative carbon isotope excursion. The resulting abrupt greening of the Central Asian steppe-desert would have enabled mammal dispersal and could have played a role in carbon cycle feedbacks by enhancing soil organic carbon burial and silicate weathering. These extreme Eocene proto-monsoons, albeit different from the topography-driven Asian monsoon today, highlight the potential for abrupt shifts in Central Asian rainfall and ecosystems under future global warming.
DOI: 10.1038/s41561-023-01371-4
Source: https://www.nature.com/articles/s41561-023-01371-4