Ice Core Studies Reconstructing Greenland Climate During the Eemian and Beyond

The primary goal of this collaborative project between three institutions is to understand the extent and evolution of the Greenland Ice Sheet (GrIS) during the Eemian period (roughly 130,000 to 115,000 years ago, the last major interglacial period in Earth's history) and the deglaciation immediately preceding it ("Termination 2"). The GrIS is an important agent influencing sea level, and Arctic and global climate, on multiple timescales. Its dynamics need to be understood in the context of past climate changes, but there is little information available about the footprint, volume, and elevation of the GrIS prior to the last ice age due to the absence of continuous ice core records prior to 123,000 years ago. During the Eemian, the GrIS was perhaps half its present size, contributing on the order of 3 m to "excess" sea level rise. Characterizing the evolution of the GrIS during glacial termination 2 and the Eemian would improve our understanding of its dynamics, and enhance our ability to make projections of sea level rise during the coming centuries. Older ice does exist at the bottoms of previously drilled ice cores, but the extraction of age and climate information from this older ice is hampered by the fact that it is stratigraphically disturbed and, in many cases, contaminated with soil or bedrock material. These investigators propose several novel methods to date this disturbed and/or "dirty" ice and to extract information on climate and ice sheet extent. The investigators will combine their new measurements and other available data to develop a more complete history of the GrIS during termination 2 and the Eemian. They will work with ice sheet modelers to investigate the constraints that the Eemian data provide for the models and improve their predictive capability. These efforts have the potential to improve our ability to predict the contribution of the GrIS to sea-level rise in the coming decades to centuries. Educational and outreach activities include the training of two graduate students, inclusion of this research in summer teacher enrichment programs, a lecture series for graduate students and postdocs, and communication of the results through the news media. PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH Blunier, T., M. L. Bender, B. Barnett, and J. C. Von Fisher. "Planetary fertility during the past 400 ka based on the triple isotope composition of O2 in trapped gases from the Vostok ice core," Climate of the Past, v.8, 2012, p. 1509. Rubino, M., D. M. Etheridge, C. M. Trudinger, C. E. Allison, M. O. Battle, R. L. Langenfelds, L. P. Steele, M. Curran, M. Bender, J. W. C. White, T. M. Jenk, T. Blunier, and R. J. Francey. "Rubino, M., D. M. Etheridge, C. M. Trudinger, C. E. Allison, M. O. Battle, R. L. Langenfelds, L. P. Steele, M. Curran, M. Bender, J. W. C. White, T. M. Jenk, T. Blunier, and R. J. Francey," Journal of Geophysical Research-Atmospheres, v.118, 2013, p. doi:10.10.

本项目由三家机构联合开展，核心目标是解析埃姆间冰期（Eemian period，约13万至11.5万年前，地球历史上最近一次主要间冰期）以及此前直接的冰消期（“终止期2（Termination 2）”）中，格陵兰冰盖（Greenland Ice Sheet, GrIS）的分布范围与演化历程。格陵兰冰盖是影响海平面、北极乃至全球气候的关键因子，其作用贯穿多个时间尺度。我们需要结合过去的气候变化背景理解其动力学机制，但由于12.3万年前之前缺乏连续冰芯记录，末次冰期之前格陵兰冰盖的覆盖范围、体积与高程相关数据极为匮乏。埃姆间冰期期间，格陵兰冰盖规模或仅为当前的一半，曾导致约3米的“超额”海平面上升。阐明终止期2与埃姆间冰期内格陵兰冰盖的演化过程，将有助于深化对其动力学机制的认知，提升我们对未来数百年海平面上升趋势的预测能力。

此前钻探获取的冰芯底部存在古老冰层，但由于这些冰层存在地层扰动，且多数情况下被土壤或基岩物质污染，难以从其中提取年代与气候信息。本项目研究团队将开发数种创新性方法，对这类受扰动及/或“受污染”冰层进行定年，并提取气候与冰盖分布相关信息。团队将整合全新测量数据与现有公开资料，构建终止期2与埃姆间冰期期间格陵兰冰盖更完整的演化历史。同时，项目团队将与冰盖建模研究者合作，探究埃姆间冰期数据对冰盖模型的约束作用，优化模型的预测能力。上述研究有望提升我们对未来数十年至数百年内格陵兰冰盖对海平面上升贡献量的预测水平。

本项目的教育与科普活动包括：培养2名研究生、将本研究内容纳入夏季教师进修项目、面向研究生与博士后开设学术讲座系列，以及通过新闻媒体传播研究成果。

本研究产出的出版物如下：
1. Blunier, T., M. L. Bender, B. Barnett, 与 J. C. Von Fisher. 《基于沃斯托克冰芯（Vostok ice core）捕获气体中氧气的三重同位素组成重建过去40万年的行星宜居性》, 《古气候杂志（Climate of the Past）》, 第8卷, 2012年, 第1509页.
2. Rubino, M., D. M. Etheridge, C. M. Trudinger, C. E. Allison, M. O. Battle, R. L. Langenfelds, L. P. Steele, M. Curran, M. Bender, J. W. C. White, T. M. Jenk, T. Blunier, 与 R. J. Francey. 《Rubino, M., D. M. Etheridge, C. M. Trudinger, C. E. Allison, M. O. Battle, R. L. Langenfelds, L. P. Steele, M. Curran, M. Bender, J. W. C. White, T. M. Jenk, T. Blunier, 和 R. J. Francey》, 《地球物理研究杂志-大气卷（Journal of Geophysical Research-Atmospheres）》, 第118卷, 2013年, 页码标注为doi:10.10.