CAREER: South Greenland's Holocene Climate History Reconstructed Using Three Paleolimnological Approaches

这项授予西北大学亚罗·阿克斯福德的NSF职业生涯奖将支持一项多管齐下的努力，即破译和了解格陵兰南部过去11000年的气候历史，以及一项专注于公共科学传播和K-12科学素养的教育努力。古气候数据为我们提供了关于北极系统如何应对重大的持续气候变化的唯一经验观察。了解格陵兰过去的气候变化是如何展开的尤为紧迫，因为格陵兰冰盖的质量损失将推动未来海平面上升的一大部分。来自南格陵兰岛的现有数据暗示，那里的气候趋势可能在一系列时间尺度上与北半球其他地方观察到的趋势不同，这可能会对未来的气温变化产生影响，从而影响冰盖物质平衡。这项拟议的研究将通过开发一套格陵兰岛最南端湖泊的气候重建来评估整个全新世(过去11,000年)的明显差异。将产生的气候记录包括基于昆虫(摇蚊)组合的定量温度重建和使用以摇蚊氧-18为基础的新方法重建降水同位素(反映大气环流的变化)。第三种方法--利用冰川门槛湖的沉积物重建高山冰川波动--将限制当地的冰块平衡，并有助于进一步描述整个全新世的当地大气气候，特别是它对冰盖的影响。这项工作将使格陵兰岛冰盖外可获得的全新世地面温度连续定量重建的数量增加一倍，从而有助于整个社区努力了解北极系统如何应对持续的气候变化。数据将被纳入古数据合成，以与国际和平研究所参与此类努力的记录保持一致，并将允许更好地测试气候和冰盖模型。将使用全新世降水同位素的独立重建来评估大气环流的变化是否伴随着过去的气候变化，从而可能伴随着未来的气候变化。通过限制夏季温度和当地冰川质量平衡，并将结果与冰川地质研究进行比较，这项工作将有助于澄清冰盖边缘的大气气候在驱动冰盖变化方面的作用。这项工作还将推进两种方法：它将验证和应用一种具有广泛应用潜力的新兴同位素替代品，以及PI将领导国际合作开发新的摇摆式古温度计校准数据集。这笔赠款将培训至少两名博士生和至少五名国际极地研究本科生，并将促进一名终身教职前地球科学家的专业发展，她对她的研究的更广泛影响表现出承诺。将推进多种合作，包括与五个外国机构的冰川地质学家和古生态学家的合作。一个新的研讨会将培训与可持续发展相关的STEM领域的研究生，掌握在学术之外交流科学的技能，为未来STEM劳动力的广泛培训做出贡献。该项目将为K-12教师提供持续的专业发展，他们将把气候和能源科学带入芝加哥地区的课堂，促进美国最大的城市学区之一(芝加哥第299区)的学生接受创新的STEM教育。

This NSF CAREER award to Yarrow Axford at Northwestern University would support a multi-pronged effort at deciphering and understanding the climate history of southern Greenland over the last eleven thousand years, and an educational effort focused on public communication of science and K-12 science literacy. Paleoclimate data provide our only empirical observations of how the arctic system responds to major sustained climate change. It is especially urgent to understand how past climate change unfolded on Greenland, because mass loss from the Greenland Ice Sheet will drive a large fraction of future sea level rise. Existing data from south Greenland hint that climate trends there may differ from trends observed elsewhere in the Northern Hemisphere on a range of timescales, with potential consequences for future temperature change and thus for ice sheet mass balance. The proposed research will assess the apparent divergence through the Holocene (the last 11,000 years), by developing a suite of climate reconstructions from lakes in southernmost Greenland. Climate records to be generated include quantitative temperature reconstructions based on insect (chironomid) assemblages and reconstructions of precipitation isotopes (reflecting changes in atmospheric circulation) using an emerging method based on chironomid oxygen-18. A third approach -- reconstructions of alpine glacier fluctuations using sediments from glacial threshold lakes -- will constrain local ice mass balance and help to further characterize local atmospheric climate through the Holocene, especially its influence on the ice sheet. This work would double the number of continuous, quantitative Holocene terrestrial temperature reconstructions available from Greenland beyond the ice sheet, thus contributing to community-wide efforts to understand how the arctic system responds to sustained climate change. Data will be incorporated into paleodata syntheses, in keeping with the PI's track record of participation in such efforts, and will allow for better tests of climate and ice sheet models. Independent reconstructions of Holocene precipitation isotopes will be used to assess whether changes in atmospheric circulation accompanied past climate change, and thus might accompany future climate change. By constraining summer temperatures and local glacier mass balance, and comparing results with glacial geologic studies, this work will help clarify the role of atmospheric climate at the ice sheet margin in driving ice sheet changes. This work will also advance two methods: It will validate and apply an emerging isotopic proxy with potential for widespread application, and the PI will lead international collaborative development of a new calibration dataset for the chironomid paleothermometer. This grant will train at least two Ph.D. students and at least five undergraduates in international polar research, and will advance the professional development of a pre-tenure geoscientist who has a demonstrated commitment to the broader impacts of her research. Multiple collaborations, including with glacial geologists and paleoecologists at five foreign institutions, will be advanced. A new seminar will train graduate students in sustainability-relevant STEM fields in skills for communicating science beyond academia, contributing to broad training of the future STEM workforce. This project will provide sustained professional development for K-12 teachers, who in turn will bring climate and energy science to Chicago-area classrooms, promoting innovative STEM education for students in one of the largest U.S. urban school districts (Chicago's District 299).