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

过去一个世纪全球冰川的消退是全球变暖最明显的信号之一，但它提出了两个仍然模糊的基本问题：当前冰川范围有多不正常，以及在工业时代之前，冰川的长期趋势是什么？这个项目将重建在全新世(过去11,000年)期间，从北极到巴塔哥尼亚的12个美洲冰川长度下的冰川比今天更大和更小的频率。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。我们的结果将为观察现代气候变化提供地质学视角，并为用于模拟冰川对未来变暖的响应的计算机模型提供古测试--这对某些地区的淡水资源和全球海平面上升很重要。我们将通过在每个冰川末端的几个前冰川基岩样品上应用现场14C-10Be计时仪来重建冰川历史。这项技术能够通过量化暴露期间14C和10Be的积累以及由于14C的半衰期短得多而在冰盖时期优先损失14C来确定全新世冰川前进和后退到当前末端的哪一部分。我们的纬度断面旨在最大限度地了解冰川对轨道变化的反应，以及气候如何在低纬度和高纬度之间以及跨半球耦合。鉴于全新世冰川趋势可能在纬度上有很大不同，我们重建的广泛规模也将为评估当前世界各地的冰川消退提供所需的背景。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.