Collaborative Research: Testing the Impact of Climate Change on the Greenland Ice Sheet: Combining Past Climate Records with a Coupled Climate and Ice-Sheet Model

该项目旨在了解格陵兰冰盖对过去气候变化的反应，其最终目标是改进对其对未来变化的反应的预测。调查人员将整理过去2万年中有关冰原大小的所有可用数据。他们还将从冰和沉积物的岩心记录中收集有关地表气温、冰的积累速率和周围海洋温度的历史数据。这些气候记录将被用作区域气候和格陵兰冰盖数值模式的输入，以研究冰盖对气候条件变化的响应。对格陵兰冰盖变化的直接观测仅跨越过去几十年，因此很难确定趋势并将其与自然变率区分开来。海洋和大气变暖在推动格陵兰冰盖退缩中的相对作用也仍然缺乏约束和争论。确定过去格陵兰冰盖对气候变暖的反应可以为冰盖退缩和损失质量的速度提供重要的界限。最后一次消冰（2万至6千年前）为评估大规模格陵兰冰盖对包括大气二氧化碳上升在内的变化条件的反应提供了一个自然实验。这个项目将解决三个基本问题。1)在最后一次消冰期间，是什么驱动了冰盖的东西边缘和南部边缘之间的不同行为？这与突然的消冰气候变化有什么关系？2)大气变暖与海洋变暖在导致末次冰消期冰缘快速退缩中的相对重要性是什么？3)考虑到大规模、持续的冰川消融气候变暖，在地质记录的限制下，格陵兰冰盖向海洋输送冰的最大速率是多少？这些速率与冰盖模型的模拟结果如何比较？解决这些问题将1)为更广泛的格陵兰冰盖在变暖的世界中如何表现提供必要的见解，2)测试陆地与海洋冰缘环境对变暖的敏感性，3)测试格陵兰冰盖模型的保真度，该模型可应用于未来的模拟。调查人员将通过讲座和大众科学杂志的出版物向公众传播科学成果，并通过魔术星球可视化系统向博物馆传播电影和动画。该项目将培养一名博士后和博士生（地质年代学数据分析和数值模拟），研究古气候学、冰川学、冰川地质学和古海洋学的多学科方法。本科生将参与该项目，目标是招募地球科学领域代表性不足的群体。

This project is aimed at understanding the response of the Greenland Ice Sheet to past climate changes, with the ultimate goal of improving predictions of its response to future change. The investigators will compile all available data on the size of the ice sheet at times in the past 20,000 years. They will also gather data on the history of surface air temperatures, the accumulation rate of ice, and surrounding ocean temperatures from ice- and sediment core records. The climate records will be used as inputs to a numerical model of the regional climate and the Greenland Ice Sheet to investigate the response of the ice sheet to changes in climate conditions. Direct observations of changes in the Greenland Ice Sheet only span the past few decades, making it difficult to identify a trend and distinguish it from natural variability. The relative roles of oceanic and atmospheric warming in driving Greenland Ice Sheet retreat also remain poorly constrained and debated. Ascertaining past Greenland Ice Sheet response to a warming climate can provide important bounds on the rates at which the ice sheet can retreat and lose mass. The last deglaciation (20 to 6 thousand years ago) provides a natural experiment for assessing large-scale Greenland Ice Sheet response to changing conditions including rising atmospheric carbon dioxide.Three fundamental questions will be addressed by this project. 1) What drove the disparate behavior between west-east margins and southern margins of the ice sheet during the last deglaciation and how does this relate to abrupt deglacial climate change? 2) What is the relative importance of atmospheric versus oceanic warming in causing rapid ice margin retreat during the last deglaciation? 3) Given the large, sustained deglacial climate warming, what is the maximum rate that the Greenland Ice Sheet has delivered ice to the ocean as constrained by the geologic record and how do those rates compare with ice-sheet model simulations? Addressing these questions will 1) provide essential insight into how the broader Greenland Ice Sheet behaves in a warming world, 2) test the sensitivity of terrestrial versus marine ice-margin settings to warming, and 3) test the fidelity of a Greenland Ice Sheet model that can be applied to future simulations. The investigators will disseminate scientific results to the public through lectures and publications in popular science magazines, and to museums with movies and animations on the Magic Planet visualization system. The project will train a postdoc and Ph.D. student (geochronology-data analysis and numerical modeling) in a multi-disciplinary approach to paleoclimatology, glaciology, glacial geology, and paleoceanography. Undergraduates will work on the project, with a goal of recruiting under-represented groups in the geosciences.