冰芯包裹气体含量和氧气δ18O记录的青藏高原中全新世以来温度变化研究

Mid-Holocene is the most recent warm period in the geological history, and the climate evolution during mid-Holocene to present is thus suggested as an analog for assessing the current global warming and predicting future climate scenario. To understand the global climate changes characterized by complex spatial variability since the mid-Holocene, more high-quality and high-resolution paleoclimate data from widely distributed locations are needed. Tibetan Plateau occupies an important position in the global paleoclimate reconstruction due to its special geographical location and topographic conditions. This project is performed to reconstruct and characterize the temperature variations during mid-Holocene to present on the Tibetan Plateau using the respective proxies of air content and δ18Oatm of atmospheric O2 in both Dunde and Guliya ice cores, which are located in the marginal area of Asian summer monsoon and the Westerly wind region, respectively. Based on the comparison of the time series of air content and δ18Oatm of O2 with those of corresponding ice core δ18O and reconstructed temperature records in adjacent areas, the representativeness of the two proxies for temperature reconstruction on millennial time scale and the consistency of that behavior in Dunde and Guliya ice cores are assessed. The discrepancy of reconstructed temperature records covering the mid-Holocene to present in different climatic regions are analyzed, and its potential causes are explored. This study will provide new information on the climate evolution since the mid-Holocene, and will provide new tools for reconstructing paleoclimate preserved in ice cores from mid- to low-latitude glaciers.

中全新世是距今最近的一个大暖期，中全新世以来气候演变为评估现代全球变暖和预估未来气候变化提供历史相似型。对中全新世以来气候格局的认识唯有从更大空间上获取更多高质量、高分辨率的古气候记录来实现。青藏高原因其独特的地理位置和地形特征而在全球古气候研究中占有重要地位，本项目以青藏高原上亚洲季风边缘区的敦德冰帽和西风气候区的古里雅冰帽为研究对象，利用冰芯包裹气体含量和气体O2的δ18Oatm对温度响应的关系重建中全新世以来的温度变化，揭示亚洲季风边缘区和西风气候区温度变化特征；综合分析气体含量和O2的δ18Oatm序列与冰芯δ18O及周边重建的温度记录，评估这两个代用指标对千年尺度温度重建的代表性及其在不同冰川中的一致性；阐述青藏高原不同气候区中全新世以来温度变化的差异并探讨其可能原因。本项目的开展将为认识青藏高原中全新世以来的气候演化提供新的证据，为中低纬度地区冰川冰芯的气候重建提供新的方法。

全球变暖背景下近几十年来青藏高原升温速率显著高于全球平均。气候变暖引起的冰川退缩、多年积雪消融、冻土活动层增厚等对青藏高原生态环境保护及水资源安全提出了新的挑战。研究升温情景下青藏高原未来气候演变及其生态环境效应，对于保护青藏高原脆弱的地表环境有着重大意义。过去是未来的钥匙，中全新世是距今最近的一个大暖期，研究中全新世以来的气候演变为评估现代全球变暖和预测未来气候变化提供相似型分析。本项目以青藏高原西北部古里雅冰芯和东北部敦德冰芯为研究对象，分析了敦德冰芯稳定同位素记录揭示的过去两千年和古里雅冰芯稳定同位素记录揭示的过去百年来的气候变化；建立了冰芯样品包裹气体提取的前处理流程和测试方法；结合青藏高原西北部和东南部冰芯记录及冰川变化现状，探讨了青藏高原西北部冰川喀喇昆仑异常和东南部冰川加速退缩的可能原因；利用多年实测资料结合模型模拟，分析青藏高原西部地区冰川变化的物理过程，阐明影响冰川物质平衡的主控因素；在古里雅冰川和敦德冰川区获得大量的野外实地观测资料，包括冰面气温、高海拔降水、冰川物质平衡、冰下地形等，这些数据的积累对于冰芯记录的解释有重要贡献。本项目现有研究成果对于认识青藏高原极高海拔冰川表面物理过程、冰芯记录对气候变暖的响应及高海拔气候变化的空间差异有重要的促进作用。