长江中游2万年以来的季节分辨气候记录:季风、ENSO和太阳变化

季节分辨 石笋 温度 降水 全新世
胡超涌 2006-01 项目
【英文摘要】The climatic records at seasonal resolution could offer significant insight into climate driving mechanism. This project developed understanding of the transport path of the climatic singals captured in stalagmtes by modern deposition experiments and field monitoring on variables including climate,environment and hydrology for 5 years inside and outside Heshang Cave, Qingjiang Valley, Hubei Province. Based on the work, geochemical records in Heshang speleothems at high resolution since 9000 aBP were obtained, by which the temperature and rainfall of the past 9000 years were reconstructed respectively. The research suggested that Mg/Ca ratio corresponded to the local atmospheric circulation anomaly since 1970, which was sensitive to the global change. Actually, similar anomaly events occurred regularly in the past 530 years and the frequency matched the solar activity, indicating that the solar changes might be the driver of the climate anomalies. The smallest seasonal, interanuual and interdecadal variation of Mg/Ca ratio ocurred during the Holocene Climatic Optimum (5-6 kaBP), predicating a stable climate stage. The quantitative reconstruction of the rainfall in Southern China derived from stalagmite oxygen isotopes demonstrates that the rainfall was 8% higher than present during 6.45-5.0 kaBP, but only 3% and 4% higher during 8.2-6.4 kaBP and 5.0-3.0 kaBP. The temperature variation in the past 9000 years interpreted by P/U indicats that the temperature during Holence Climate Optimum is higher than present by 3-4℃.
【中文摘要】季节尺度的气候记录对了解过去气候变化的驱动机制有重要作用。项目对湖北清江和尚洞气候、环境、水文和水化学等进行了野外现场监测和碳酸盐沉积的模拟试验,查清气候信号的传输途径及其记录过程;在此基础上,高分辨率提取了和尚洞过去9000年的石笋地球化学记录,分别重建了长江中游9000年以来的温度和降水。结果发现,Mg/Ca较好地反映了本地区1970年代以后大气环流的异常,对全球变化有敏感的响应。然而此类异常事件在过去530年中常有发生,且发生频率与太阳活动相同,指示气候异常的驱动力可能是太阳变化。全新世大暖期(5-6kaBP),石笋Mg/Ca的季节、年际和年代际变化幅度最小,指示一个稳定的气候条件;石笋氧同位素定量重建了中国南方降水曲线表明,研究区降水在8.2-6.4kaBP比现在多3%,6.4-5.0kaBP,多8%;5.0-3.0kaBP,多4%;利用P/U研究了长江中游9000年以来的温度变化,发现全新世大暖期比现在高3-4℃。