青藏高原典型冰川雪-冰沉积后过程对冰芯稳定同位素温度重建影响定量研究

The universality and mechanism-based variability of ice cores stable isotopes as valid proxy of temperature change in the Tibetan Plateau is still controversial. Based on my previous studies on water vapor stable isotopes and ice core stable isotopes, this project focuses on the systematic monitoring of isotopic compositions of atmospheric water vapor - precipitation - surface snow - shallow ice cores during the monsoon and non-monsoon seasons on the Muztagata controlled by the westerlies all year round, Dasuopu controlled by the Indian summer monsoon in summer and Guliya ice cap situated between the two in the Tibetan Plateau, simultaneously. Combined with isotopic model, we are trying to quantify the magnitude of post-depositional processes affecting the isotopic composition of surface snow, clarify variations and key factors controlling isotopic exchange processes between the atmospheric vapor, precipitation and surface snow beyond the westerlies and the Indian summer monsoon, and reveal the influence of post-depositional processes on the reconstructed temperature based on ice core stable isotopes in the Tibetan Plateau. Our study will help to provide critical methods on exact reconstruction of temperature by ice core stable isotopes in the Tibetan Plateau, and estimate the climate change impacts and regional feedback.

青藏高原冰芯稳定同位素作为有效温度指标的普适性和空间差异机制仍然存在争议。在本申请人已开展的青藏高原水汽稳定同位素研究和冰芯稳定同位素记录研究基础上，本项目选择在青藏高原全年受西风控制的慕士塔格冰川、夏季受印度季风控制的达索普冰川和二者之间关键区的古里雅冰帽开展季风期和非季风期冰川积累区的连续水汽-降雪-表雪-浅冰芯氢氧稳定同位素同期观测，结合稳定同位素模型模拟，量化雪-冰沉积后过程对表雪氢氧稳定同位素的影响幅度，阐明西风-季风不同传输下水汽-降雪-表雪的氢氧稳定同位素交换过程和其主要控制因素，揭示雪-冰沉积后过程对青藏高原冰芯稳定同位素所重建的温度变化的影响。本项目的开展将为利用冰芯稳定同位素记录剔除雪-冰沉积后过程影响进行更精确的古温度重建提供关键方法，也可为预估未来全球气候变化情景下的区域气候影响与响应提供重要科学依据。

本项目通过开展青藏高原典型冰川表面不同海拔梯度表雪样品采集测试和大气水汽稳定同位素及气象要素的连续观测，首次获得了冰川表面大气水汽稳定同位素随海拔高度的变化特征，分析了其与同期降水和表雪稳定同位素变化的关系及其可能的气象条件影响机制。本项目还结合稳定同位素分馏模型和ECHAM5-wiso模型，初步阐明了西风-季风不同传输下水汽-降雪-表雪的氢氧稳定同位素交换过程和其主要控制因素，揭示了雪-冰沉积后过程对青藏高原冰芯稳定同位素所重建的温度变化的影响。本项目研究结果为青藏高原冰芯稳定同位素记录的气候解释提供了新的科学依据。本项目完成了2名硕士研究生（其中1名留学生）培养和1名博士研究生培养，发表了3篇中文核心期刊论文和3篇英文国际期刊论文，组织了学术会议、专业课程授课等多种形式的国际合作交流。