Collaborative Research: Reconstructing Holocene glacier lengths through time to address climate model-data disagreements

全球范围内冰川的持续退缩是现代气候变化的一个显著后果。冰川对过去气候变化的反应形成了评估其未来行为的概念基础，这反过来又为依赖冰川供水进行灌溉、消费和能源使用的人们提供了关键信息。这项研究产生了新的地质数据，记录了北美和南美过去12000年的冰川和气候变化。该项目正在利用新的统计学、冰川学和气候学模型评估新的地质数据，以确定为什么研究地区的冰川可能对过去的气候变化做出不同的反应。这项工作的结果为了解过去的冰川变化提供了有价值的信息，这将有助于更好地评估这些冰川的未来变化。本项目为多名本科生和研究生提供科学的培训和指导。国际合作也通过大学伙伴关系得到加强。作为该项目的一部分，公共宣传活动包括与K-12合作伙伴一起建立课程，参与全州范围的科学节，以及与通过大学水平项目招募的代表性不足的学生进行本科指导。根据最近的模式资料同化，从全新世早期到晚期，全球平均气温升高了~0.5°C。冰川是这种气候变化的敏感记录者；然而，从全新世早期到晚期，北美和热带几个地方的冰川都在扩张，这与最新的气候重建结果不一致。这项研究考察了从阿拉斯加到南巴塔哥尼亚的六个地点的全新世高山冰川状况，以解决这一明显的差异。通过结合基岩暴露年代和统计/冰川学模型，该项目将冰川长度变化的年表与过去的气候条件联系起来，以解决有关全球、半球和区域气候变化的未解决问题。本研究的目的有三个：1)在从北美到南美的大纬度范围内的六个地点，用配对的14C/10Be暴露年龄限制冰川长度的变化；2)利用基于贝叶斯推断的蒙特卡罗正演模型确定这六个地点的冰川长度随时间的变化；3)利用现有气候模拟和古代用气候重建强迫的冰川学模式，从数据和正演模式输出中确定解释冰川长度历史的合理气候情景。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 ongoing retreat of glaciers worldwide provides a striking visual consequence of modern climate change. How glaciers responded to past climate changes forms the conceptual basis for evaluating their future behavior, which in turn provides critical information for people who depend on the water supply from glaciers for irrigation, consumption, and energy usage. This research is generating new geologic data that document glacier and climate changes in the past ~12,000 across North and South America. The project is evaluating the new geologic data using novel statistical, glaciological, and climatological models to determine why glaciers in the study region may have responded differently to past climate shifts. Outcomes of this work provide valuable information for understanding past glacier changes which will lead to a better ability to assess future changes of those same glaciers. This project provides scientific training and mentoring for multiple undergraduate and graduate students. International collaborations are also being strengthened through university partnerships. Public outreach occurring as part of this project includes curriculum building with K-12 partners, participation in statewide science festivals, and undergraduate mentoring that is engaging with underrepresented students recruited through college level programs.Global mean temperatures from the early to late Holocene have warmed by ~0.5°C based on a recent model-data assimilation. Glaciers are sensitive recorders of such climate change; however, glaciers across North America and at several locations in the Tropics expanded from the early to late Holocene, at odds with this latest climate reconstruction. This research is examining Holocene alpine glacier conditions at six locations extending from Alaska to southern Patagonia to address this apparent discrepancy. Through a combination of bedrock exposure dating and statistical/glaciological modeling, the project is relating the chronology of glacier length changes to past climate conditions to address unresolved questions regarding global, hemispheric, and regional climate changes. The objectives of this research are threefold: 1) constraining glacier length changes with paired 14C/10Be exposure ages at six locations that span a large latitudinal range from North to South America; 2) determining glacier length through time at these six locations by applying a Monte Carlo forward model guided by Bayesian inferences from these newly collected data; and 3) using a glaciological model forced by existing climate simulations and paleo-proxy climate reconstructions to determine plausible climate scenarios that explain the glacier length histories from the data and forward model output.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.