中国西部及其毗邻区域过去2000年气候与环境变化研究

中国西部 过去2000年 温度变化 降水变化 环境演变
杨保 2007-01 项目
【英文摘要】From the comparison of temperature reconstruction and GCM simulation results, temporal characteristics, amplitude, periodicity and forcing mechanism of temperature variations in China during the last 2000 years are revealed. We present tree ring-width records from south Tibet and southeast Tibet of the southern Tibetan Plateau (TP) which span from 1612-1998 AD and from 1380-1998 AD respectively, which are close to the highest tree positions found on the TP and worldwide. Based on these chronologies, temperature variation and its cause are clarified for the last 600 years. It is corroborated that ice-core oxygen isotopes derived from the Tibetan Plateau are a good indicator of temperature change at timescales ranging from annual to centennial. Climate variations in arid western China during historical times are studied and clarified. We present a 550-year ice-core pollen record with a 5-year resolution from the Puruogangri ice field in the central Tibetan Plateau. This proxy series is the first high-resolution ice-core pollen record spanning the last 550 years for the central Tibetan Plateau.Together with δ18O and glacial accumulation records, the response of vegetation to climate change over the past 500 years was revealed.Desert vegetation dominated during 1450-1640 AD, a time period characterized by cold-wet climate, while steppe vegetation expanded during 1640-1915 when warm-dry climate prevailed. Afterwards, during a cold and humid period, desert vegetation expanded again.We established a chronology of monsoonal temperate glacier fluctuations in China during the last two millennia, and reveal decadal to centennial glacial fluctuations. Three main periods of glacier advances are identified: around 200-600 AD, 800-1150 AD, and 1400-1920 AD.Dust storm events and their relation to climate changes in Northern China during the past 1000 years were analyzed by using different paleoclimate archives such as ice cores, tree rings, and historical documents. The results show that in the semiarid region, the temperature and precipitation series were significantly negatively correlated to the dust storm frequency on a decadal timescale.It is found that the thermal conditions in the Himalayas and on the Tibetan Plateau and associated glacial boundary conditions may have been predominantly responsible for variations of the ASM intensity and for a latitudinal movement in the mean position of the ITCZ on decadal to centennial timescales.
【中文摘要】(1)通过气候重建资料和GCM模拟结果的对比分析,揭示了中国过去2000年温度变化的过程、幅度、周期、规律和动力学机制;建立了青藏高原海拔最高(4750米)的树轮年表,据此分别恢复了高原南部近400年、高原东南部及其毗邻地区以及整个青藏高原近600年来的温度变化历史,揭示了年代际温度变化特征,探讨了气候变化的驱动机制;证实青藏高原冰芯中氧同位素在年、十年至百年尺度上是温度变化的代用指标;开展了中国西部干旱区历史时期气候变化研究,建立了近2000年气候变化序列,阐明了其变化规律。首次建立了青藏高原中部过去150年以来分辨率为1年、过去550年以来分辨率为5年的花粉序列,据此高分辨率恢复了该区域小冰期以来的植被变化历史,分析了近550年来青藏高原中部植被变化对气候变化的响应机制。建立了过去2000年中国季风温冰川波动年表,揭示了季风温冰川年代-百年尺度的变化过程,深化了对中国季风温冰川短尺度变化规律的认识;揭示了中国北方干旱半干旱地区近2000年来沙尘事件与气候变化的关系,指出在年代至世纪时间尺度上,沙尘活动主要受气候变化的控制;从百年尺度证明青藏高原作为夏季热源驱动亚洲季风的事实.