热带玛珥湖深钻的轨道尺度高分辨环境记录与海陆对比

The southeastern end of Chinese mainland, located in the immediate north of the South China Sea, is a key region of research on interaction between land and sea. The Maar lakes located in the Leizhou Peninsula, yielding thick lacustrine sediments, record long sequence of lake evolution and paleoclimate of orbital scale. The present project plans to drill several cores in the lakes with a total length more than 300 m. The multidisciplinary studies including stable carbon isotope, C/N ratio, pollen and spore, biomarker compounds, magnetic susceptibility and grain-size will be carried out. The purpose of this research is to quantitatively reconstruct the Quaternary ecosystem and climate changes since ~500 ka BP. In particular, the project concerns the study on clarification of the vegetation response on global and regional climate events, the sensitivity of pollen spectra to the orbital climate cycles and the rapid change, and the tropical floristic and biome changes during the glacial episode driven by the lowering of temperature and rainfall. The study of the present project will provide new data as a climate proxy of long sequence, which make it possible to correlate with the records of terrestrial stalagmites and marine deep-sea cores. Consequently, the new result helps better understand the interaction between land and sea, as well as monsoon circulation, and provides solid scientific information of regional response on global changes.

雷州半岛位于中国大陆东南端，是东亚季风水汽向陆地输送的前锋关键地带，该区的玛珥湖沉积厚度大，其沉积物敏感地记录了轨道尺度的热带植被演替、东亚季风和太阳辐射变化的丰富信息。本项目计划在青桐洋和田洋玛珥湖中心部位进行总进尺300余米的钻探取样，通过高分辨率稳定碳同位素、元素比值、孢粉、生物标志化合物、磁化率等多种替代指标的古环境分析，重建热带地区50万年以来的生态系统和气候变化，辨析华南热带地区气候波动的全球性因素和区域性影响，揭示热带陆地系统对轨道尺度太阳辐射和非轨道快速气候变化事件的敏感程度，探明冰期阶段热带植被生态系统对温度和降雨的响应幅度。本研究的古环境参数可以与长序列的石笋记录以及深海记录进行对比，从而获得较大空间尺度的全球变化和区域响应的新认识，进一步理解海-陆相互作用和季风过程，为全球气候变化的区域响应提供新的科学论据。

雷州半岛的玛珥湖沉积厚度大，敏感地记录了轨道尺度东亚季风和太阳辐射变化的丰富信息。本项目在田洋和九斗洋玛珥湖中心部位完成总进尺310余米的钻探取样。根据田洋平行钻孔的古地磁及气候地层对比建立了可靠的年代框架，获得了高分辨率稳定碳同位素、孢粉、生物标志物、磁化率等指标的古环境分析结果，重建了热带地区35万年以来的生态系统和气候变化，认为热带地区多个冰期-间冰期旋回的植被变化特征为草本-木本之间的交替，与碳同位素获得的C3/C4交替十分吻合。综合指标揭示了轨道尺度热带气候的波动以降雨量变化为主，表明中更新世以来冬季风的逐渐增强对热带季风区的植被影响是显著的，频谱分析显示10万年周期的轨道尺度太阳辐射和冰盖驱动对热带气候的影响。与长序列的深海、冰芯、石笋记录对比发现，太阳辐射、冰川进退、跨南北半球气压变化、ITCZ 的南北移动和海平面变化等影响是导致热带植被周期性变化的主要因素，而冰期阶段CO2对热带森林-草地的植被更替的贡献也是不能忽视的原因之一。本研究获得东亚热带区域生态系统对长时间尺度气候变化响应的新认识，为理解季风过程的热带演变提供了重要数据，为区域气候变化的动力学机制模拟提供了新的长时间尺度的重要科学论据。