Collaborative Research: Holocene glacier length variations along the spine of the American Cordilleras and their climatic significance

在过去的一个世纪里，全球范围内冰川的退缩是全球变暖最明显的信号之一，但它提出了两个基本的问题，仍然模糊不清：目前的冰川范围有多反常？在工业时代之前，冰川的长期趋势是什么？这个项目将重建在全新世（过去11000年）期间，从北极到巴塔哥尼亚，横跨整个美洲的十几座冰川比现在更大或更小的频率。我们采取以社区为基础的方法来降低成本，活跃的冰川科学家在他们自己的实地活动中免费收集样本，为这个项目做出贡献。我们的研究结果将提供一个观察现代气候变化的地质视角，并为用于模拟冰川对未来变暖反应的计算机模型提供一个古测试——这对某些地区的淡水资源和全球海平面上升很重要。我们将利用原位14C-10Be计时器对每个冰川末端的几个前冰川基岩样本进行重建冰川历史。这项技术能够通过量化暴露期间14C和10Be的积累，以及14C在冰盖时期的优先损失（由于其半衰期短得多），来确定冰川在全新世的哪个部分超越了它目前的终点。我们的纬度样带旨在最大限度地了解冰川如何响应轨道变化，以及气候如何在低纬度和高纬度之间以及整个半球之间耦合。考虑到全新世冰川的趋势可能会随着纬度的变化而发生很大的变化，我们的大规模重建也将为评估当前世界各地的冰川退缩提供所需的背景。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The worldwide retreat of glaciers over the past century is one of the clearest signals of global warming, but it raises two basic questions that remain hazy: how anomalous are current glacier extents, and what were long-term glacier trends prior to the industrial era? This project will reconstruct how often during the Holocene (the last 11,000 years) a dozen glaciers down the length of the Americas, from the Arctic to Patagonia, were larger versus smaller than today. We take a community-based approach to reduce cost, with active glacier scientists collecting samples gratis during their own field campaigns to contribute to this project. Our results will provide a geologic lens through which to view modern climate change, and offer a paleo-test for computer models used to simulate glacier responses to future warming -- important to freshwater resources in some areas and global sea level rise. We will reconstruct glacier histories by applying the in situ 14C-10Be chronometer to several samples of proglacial bedrock at each glacier terminus. This technique is able to determine what portion of the Holocene a glacier advanced beyond and retreated behind its current terminus by quantifying the buildup of both 14C and 10Be during periods of exposure and the preferential loss of 14C during episodes of ice cover due to its much shorter half-life. Our latitudinal transect is designed to maximize understanding of how glaciers responded to orbital variations, as well as how climate may have been coupled between the low and high latitudes and across the hemispheres. Given that Holocene glacier trends may have varied substantially with latitude, the broad scale of our reconstructions will also provide the context needed for evaluating current glacier retreat around the world.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.