Collaborative Research: 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.

本联合项目由三家机构共同发起，核心目标为解析埃姆间冰期（Eemian period，约13万至11.5万年前，地球地质历史上末次大型间冰期）及其紧邻的冰消阶段（"终止事件2（Termination 2）"）期间，格陵兰冰盖（Greenland Ice Sheet, GrIS）的规模范围与演化历程。

格陵兰冰盖是影响海平面、北极乃至全球气候的关键因子，其作用覆盖多时间尺度。由于12.3万年前尚无连续冰芯记录留存，针对末次冰期前格陵兰冰盖的分布范围、体积与高程的相关记录十分匮乏。埃姆间冰期期间，格陵兰冰盖规模或仅为当前的一半，曾贡献约3米的"超额"海平面上升量。

厘清终止事件2与埃姆间冰期期间格陵兰冰盖的演化过程，有助于深化对其动力学机制的理解，进而提升我们对未来数百年海平面上升的预测能力。此前已钻探的冰芯底部虽存在古老冰体，但受地层序列扰动影响，且多数样品被土壤或基岩物质污染，导致难以从这些古老冰体中提取年代与气候相关信息。

本研究团队提出多种创新性方法，以对这类受扰动的"脏冰"进行定年，并提取其中的气候与冰盖范围相关信息。研究团队将整合新测得数据与现有公开数据，构建终止事件2与埃姆间冰期期间格陵兰冰盖更完整的演化历史。同时，团队将与冰盖模型研究者合作，探究埃姆间冰期相关数据对模型的约束作用，优化模型的预测能力。此类研究有望提升我们对未来数十年至数百年间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推广活动包括培养2名研究生、将本研究内容纳入夏季教师能力提升研修项目、面向研究生与博士后开设系列学术讲座，以及通过新闻媒体向公众传播研究成果。

本研究产出的学术出版物如下：
1. Blunier, T., M. L. Bender, B. Barnett, 及 J. C. Von Fisher. 《基于沃斯托克冰芯捕获气体的氧气三重同位素组成重建过去40万年行星宜居性》，*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, 及 R. J. Francey. （原文此处存在作者列表重复内容，按原文保留），*Journal of Geophysical Research-Atmospheres*，第118卷，2013年，doi:10.10.