中全新世以来长江中游地区年际-年代际干旱强度与频次的年层石笋记录研究

Weather and climate extremes are heavily examined in terms of global change. Extreme precipitation event (prolonged drought) increasingly occurs along with the global warming and monsoon strengthening over the last decades. Nevertheless, it is unclear if the present deterioration of hydrologic climate links to the warming and monsoon anomaly due to green-house gasses emission. It is therefore important to understand the natural history of extreme precipitation event in the long past. However, reconstructing past precipitation is rather difficult at annual to decadal scales, partly because of the lack of precise chronology and solid proxy interpretation. It is observed, from our 10-year monitoring study at Heshang Cave over middle reaches of the Yangtze River, that stalagmite Mg/Ca in the cave reflects annual precipitation variability at the site and can be considered as a solid proxy for palaeo-drought. In this proposed study, by applying the LA-ICP-MS we will conduct seasonally resolved elemental analyses on a classic and annually-laminated stalagmite from the Heshang cave. Combining with detailed proxy calibration efforts, we will uncover the annual precipitation variation at this site since the middle Holocene and the patterns of drought occurrence under different atmosphere-oceanic circulation states. The result of this study may help to assess the anthropogenic forcing of current extreme precipitation anomaly and provide constrains for the drought projection for future scenarios.

极端气候是全球变化研究的热点。随着全球变暖和北半球季风增强，最近几十年我国东-南部地区极端降水事件（特别是持续性旱灾）频发。但是，当前的水文气候异常是否与人类温室气体排放造成的高温、强季风背景有关，尚不清楚，因此，亟需认识过去极端降水事件变化的自然背景。然而，受年代学和气候替代指标等限制，重建过去年际-年代际降水变化的长期历史记录相当困难。我们对湖北和尚洞的十年监测发现，石笋Mg/Ca在年际尺度上反映了当地的降水变化，是干旱事件的可靠指标。本项目拟应用LA-ICP-MS对和尚洞一根经典年层石笋开展季节分辨率的Mg/Ca分析，并在详实的指标校正基础上，重建中全新世以来长江中游地区降水的年际变化历史，揭示在不同气候态下干旱事件的规律及其驱动机制，为评估导致当前极端降水异常的人为因素和预测未来旱灾的发生趋势提供参考。

随着全球变暖和北半球季风增强，我国东-南部地区近几十年来极端降水事件（特别是持续性旱灾）频发。当前的水文气候异常是否与人类温室气体排放造成的高温、强季风背景有关？目前尚不明确。因此，认识过去自然背景下极端降水事件的发生规律十分重要。然而，受年代学和气候替代指标等限制，重建过去年际-年代际降水变化的长期记录非常困难。我们在湖北和尚洞开展多年连续高频环境监测的基础上，发现了石笋Mg/Ca记录在年际时间尺度上反映了当地的降水变化，是干旱事件的可靠指标。我们应用LA-ICP-MS对和尚洞一根经典年层石笋开展了季节分辨率的Mg/Ca分析，结合详实的现代过程研究和指标校正，重建了中全新世以来长江中游地区的降水历史，探讨了在不同气候平均态下该地区干旱事件的发生规律及其驱动机制。