西昆仑山崇测冰帽末次间冰期以来冰芯记录及冰川变化对气候的响应

Climate change during the last interglacial period draws much attention because of similarity of climatic features between the current and last interglacials, regarded as a likely analogue to future projected climate. It’s suggested that the west Kunlun Mountains may be the only place in the west China to recover ice cores with a potential age reaching the last interglacial period. Here we make use of two drilled ice cores to-the-bottom (with length of 135.30 m and 131.92 m, respectively) and another two proposing ice cores to-the-bottom from the thickest site (>210 m, which was deduced from the penetratign radio sounding results) of the Chongce Ice Cap in the west Kunlun Mountains, for performing multi-type and high-resolution time series of climatic proxies. The climatic change since the last interglacial period will be reconstructed based on a reliable ice core dating by applying novel methods. Moreover, we will perform a detailed survey on the Chongce Ice Cap to decipher its dynamic features, and ascertain the coverage of the ancient glaciers in the west Kunlun since the last glacial to understand their response to the past climatic conditions that were reconstructed by the ice cores and the other kinds of climatic archives. Our results might have important implications for future climtic prediction and mountainous glacier variation.

末次间冰期气候特征与现代气候具有一定的相似性，为预测未来气候变化提供重要的参照，因此末次间冰期气候特征备受关注。以往结果表明，西昆仑山地区可能是在我国西部寻找时间尺度达末次间冰期冰芯记录的唯一适合区域。本申请项目基于已在西昆仑山崇测冰帽钻取的两支透底冰芯（长度分别为135.30 m、131.92 m）和拟在崇测冰帽最厚处（雷达测量>210m）钻取的另两支透底冰芯，进行冰芯多参数、高分辨率气候环境代用指标的测试。在采用多种创新方式进行准确冰芯定年的基础上，重建该地区末次间冰期以来的气候变化。同时，通过对崇测冰帽现代测量和古冰川范围的确定，获取所研究地区的冰川动力学特征及其末次冰期以来的冰川变化过程，并结合末次间冰期以来冰芯以及其他类型气候记录，探讨末次冰期以来冰川变化对气候的响应。本申请项目的研究结果对于预估未来气候状况以及山地冰川变化趋势具有重要意义。

西昆仑山古里雅冰芯年代据认为超过50万年（甚至可达~76万年），并根据古里雅冰芯稳定同位素记录重建了11万年以来的气候变化，因此西昆仑山地区可能是在我国西部寻找时间尺度达末次间冰期冰芯记录的唯一适合区域。本项目在西昆仑山崇测冰帽（距古里雅冰芯钻取点位置约30km）钻取了四支透底冰芯（长度分别为216.6m、208.6m、135.8m和133.8m），首次对崇测冰芯底部碎屑物进行了光释光定年工作，得到释光年龄为4.2±0.4万年，这也是崇测冰芯年龄的上限。再者，基于崇测冰芯的14C、210Pb、氚和β活化度等分析结果，运用冰川流动模型，进一步界定崇测冰芯的底部年龄介于8-9ka，上述定年结果比古里雅冰芯小了~2个量级。通过对比崇测冰芯和古里雅冰芯的稳定同位素剖面，二者具有显著的一致性，表明二者的年龄范围应该类似，因此需要重新审视青藏高原冰芯的以往重建结果。基于更新的青藏高原冰芯年代框架，以及稳定同位素、微粒、主要阴阳离子、痕量元素等的测量结果，高分辨率地重建了青藏高原全新世气候和环境变化。比如气候重建结果表明青藏高原中全新世的温度升高趋势，更新了古里雅冰芯原来认为的中全新世降温观点。基于遥感资料重建了近几十年来西昆仑山地区的冰川变化，并将根据冰川底部年代进一步确定全新世青藏高原冰川退缩情况。本项目更正了以往的错误认识，建立了青藏高原冰芯的新年代框架，并开拓了新的冰芯研究发展方向。