苟鲁措记录的青藏高原北部全新世降水变化研究

Interplay between Asian monsoon and the westerlies systems controls climatic and environmental changes on the Tibetan Plateau, resulting in an out-of-phase pattern of precipitation variation between northern and southern Tibetan Plateau on decadal and century time scales during the past several centuries. However, it is not clear whether such an out-of-phase pattern of precipitation existed on a millennial time scale during the Holocene due to the lack of high resolution precipitation record with robust chronology from the northern Tibetan Plateau. In this project, we choose Goulu Co (Co means Lake) from the northern Tibetan Plateau as our study site. High-quality, continuous sedimentary cores will be drilled from the lake. The reliable chronology of sediment core will be established using 210Pb/137Cs dating of sediments and AMS14C dating of well-preserved plant fragments, charcoals, and organic matters. Based on systematic study of modern process in the drainage area, high-resolution and well-dated Holocene records of precipitation amount and moisture sources from the northern Tibetan Plateau will be reconstructed with proxies of XRF-based elements, carbonate oxygen isotopes and leaf wax hydrogen isotopes, in addition to other proxies including carbonate content, grain size, TOC and environmental magnetic parameters. The reconstructed precipitation history will be compared with Holocene precipitation records from southern Tibetan Plateau and those from typical westerlies-dominated regions beyond the Tibetan Plateau, extracting the spatial-temporal pattern of Holocene precipitation across the Tibetan Plateau, and the interplay between Asian monsoon and the westerlies during the Holocene and the possible forcing mechanism. The study results will further provide key and basic data and references for dealing with modern ecological and environmental changes on the plateau and for predicting the trend of future climate change.

季风与西风相互作用控制了青藏高原的气候与环境变化，致使高原在过去数百年以来的年代际、百年时间尺度上存在南北相反的降水变化格局。然而，由于青藏高原北部缺少年代可靠的高分辨率全新世降水记录，全新世千年时间尺度上高原降水是否存在南北反相变化模态仍不清楚。本项目选择青藏高原北部苟鲁措为研究对象，钻取连续的高质量沉积物岩芯，通过210Pb、137Cs和14C等多种放射性核素测年手段建立岩芯可靠的年代框架；利用XRF元素、碳酸盐氧同位素、叶蜡氢同位素及其他常规指标，在详细的湖泊流域现代环境过程研究基础上，高分辨率地重建全新世以来研究区降水和水汽来源变化历史。将重建的结果与高原南部全新世降水记录以及典型西风影响区代表性气候记录开展对比，探讨青藏高原全新世气候变化的时空异同、亚洲夏季风与西风相互作用历史及其驱动机制。研究结果将为应对当下青藏高原生态环境变化以及预测未来气候变化趋势提供理论参考。

季风与西风相互作用控制了青藏高原的气候与环境变化，致使高原在过去数百年以来的年代际、百年时间尺度上存在南北相反的降水变化格局。然而，由于青藏高原北部缺少年代可靠的高分辨率全新世降水记录，全新世千年时间尺度上高原降水是否存在南北反相变化模态仍不清楚，更无从得知高原腹地湖泊及其流域的生态环境对气候变化的响应过程。本研究聚焦高原腹地开放湖泊班德湖，基于BDH19A岩芯的植物残体AMS14C年代建立了可靠的年代框架，通过粒度、元素、矿物、自生碳酸盐碳氧同位素及正构烷烃等多指标，重建了近10ka (1ka=1cal kyr BP)青藏高原中部的气候变化与生态环境响应过程。结果显示，青藏高原腹地在全新世以来表现出北半球夏季太阳辐射控制下夏季风降水逐渐减少的季风模式，导致流域和湖泊生产力持续降低，区域风沙活动整体增强。在千年时间尺度上，10~8ka高原中部夏季风降水量最大，但可能由于植被覆盖度较高，流域径流侵蚀减弱，风沙活动减少；7~5.4ka和4.2~2.2ka夏季风降水维持高值，入湖径流增加，促进流域和湖泊生产力提高，风沙活动受到抑制；相反，8~7ka、5.4~4.2ka和2.2ka以来高原中部风沙活动的加剧是对夏季风快速衰退的响应，当前班德湖流域风沙环境是过去2ka干旱风沙环境的延续与加剧。

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