Collaborative Research: Toward placing contemporary Arctic summer warming in a millennial perspective with a pan-Arctic record of Neoglacial crysophere expansion

米勒/考夫曼：用新冰川冰川扩张的泛北极记录将当代北极夏季变暖置于千禧年的视角非技术总结。北极的冰川尺寸是由夏季温度决定的，但自冰河时代结束以来，阿拉斯加冰川尺寸的变化很难受到限制。为了应对最近的北极变暖，阿拉斯加布鲁克斯山脉的冰川正在迅速消退，在特殊的环境下，在冰很薄的平缓斜坡上，冰川起到了保存剂的作用，而不是腐蚀剂，保存了完好无损的微小苔原植物，在遥远的过去冰层在该地点扩张之前就存活了下来。该项目的目标是访问布鲁克斯山脉最有可能保存冰川的地点，而不是侵蚀景观，我们预计那里的苔原植物将随着冰川的消退而重新暴露出来。这些植物的放射性碳年代记录了过去夏季变冷的时间，允许冰在这些地点扩张，并提供了最可靠的证据，证明在过去的北极夏季，什么时候足够冷，允许冰川生长。将阿拉斯加冰埋植物的年龄与其他北极地区暴露的植物的年龄进行比较，将使我们能够更好地了解半球尺度上的大规模气候变化。这些结果是对用于预测未来气候的气候模型的测试。用于未来预测的相同模型可以反向运行，以预测过去的气候演变。如果这些模型预测的过去气候变化模式与北极冰层埋藏植物的年龄记录的类似，我们对气候模型可靠预测未来气候的能力的信心就会增强。如果这些模型未能预测出与植物年龄相似的模式，那么这些模型很可能低估了气候系统的某些方面。布鲁克斯山脉冰川在全新世期间的尺寸变化，是夏季气温变化的主要指标，但限制很差。在冰川以寒冷为基础的缓坡地形上，冰川通常不会被侵蚀，而是充当特殊的保存剂，保存因冰层膨胀而死亡的微小冻土带植物。布鲁克斯山脉的冰川迅速消退，现在暴露出的景观很可能保存着被晚全新世冰川扩张杀死的原地苔原植物，它们的放射性碳年龄决定了持续寒冷的夏季。该项目将访问最有希望的地点，寻找随着冰缘消退而出现的冰埋植物，并利用北亚利桑那大学由美国国家科学基金会支持的新型加速器质谱仪进行测年。我们预计，由此产生的过时植物的综合概率密度函数将产生反映冰扩张/寒冷夏季事件的年龄群，这可以与北大西洋北极的结果进行比较，并共同作为目前正在与CMIP-6进行的共同时代气候模拟的目标。随着气候变化的加速和气候素养的滞后，与更广泛的公众沟通气候变化比以往任何时候都更加重要。尽管人们普遍认为阿拉斯加(和其他地方)的冰川正在迅速消退，但人们对这场衰退到底有多不寻常却知之甚少。这项研究将把冰川衰退放在千禧年的角度来看，很可能说明目前的变暖是数千年来前所未有的，这一概念很容易被普通公众理解。为了推进公众宣传，我们将支持一位经验丰富的平面设计师将我们的科学转化为阿拉斯加公民和更广泛的美国社区可以访问的形式。该奖项反映了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。

Miller/Kaufman: Toward placing contemporary Arctic summer warming in a millennial perspective with a pan- Arctic record of Neoglacial crysophere expansionNon-technical summary. Glacier dimensions in the Arctic are set by summer temperature, but changes in the dimensions of Alaskan glaciers since the end of the ice age are poorly constrained. In response to recent Arctic warming, glaciers in the Brooks Range, Alaska are receding rapidly, and in special settings, on gentle slopes where the ice is thin, glaciers act as preservation agents, rather than erosive agents, preserving intact tiny tundra plants living before the ice expanded over that site in the distant past. The goal of this project is to visit the most likely sites in the Brooks Range where glaciers preserved, rather than eroded the landscape, where we expect tundra plants are being re-exposed as ice recedes. The radiocarbon ages of these plants document when past summers grew colder, allowing ice to expand across these sites, and provide the most reliableevidence of when in the past Arctic summers cooled enough to allow glaciers to grow.Broader Impacts. Comparing the ages of ice-entombed Alaska plants to ages of plants exposed in other Arctic regions will allow us to better understand large-scale climate change on a hemispheric scale. These results serve as tests for climate models that are used to predict future climate. The same models used for future projections can be run in reverse to predict climate evolution in the past. If the models predict similar patterns of past climate change as documented by the ages of ice-entombed plants across the Arctic, our confidence in the ability of climate models to reliably predict future climate is increased. If the models fail to predict patterns similar to the plant ages, then it is likely the models have underestimated certain aspects of the climate system.Technical summary. Changes in the dimensions of Brooks Range glaciers through the Holocene, a primary proxy for changes in summer temperature, are poorly constrained. Where glaciers are cold-based and on gently sloping terrain, they often do not erode, but act as exceptional preservation agents, preserving tiny tundra plants killed by expanding ice. Rapid ice recession across the Brooks Range is now exposing landscapes likely to preserve in situ tundra plants killed by late Holocene ice expansion, with their radiocarbon ages defining episodes of consistently cold summers. This project will visit the most promising sites to look for iceentombed plants emerging as the ice margins recede, and take advantage of the new NSF-supported accelerator mass spectrometer at Northern Arizona University for dating. We expect the resultant composite probability density functions of dated plants to produce age clusters reflecting episodes of ice expansion/cold summers, which can be compared with results from the North Atlantic Arctic, and collectively serve as targets for Common Era climate modeling now underway with CMIP-6.Broader Impacts. Communicating climate change with the wider public is more important than ever as climate change accelerates and climate literacy lags. Although it's widely understood that glaciers in Alaska (and elsewhere) are rapidly receding, there is less understanding of how unusual this recession really is. This study will place glacier recession in a millennial perspective, likely illustrating that current warming is unprecedented over thousands of years, a concept easily grasped by the general public. To advance public outreach, we will support an experienced graphic designer to translate our science to a form that is accessible to the citizens of Alaska and the broader US community.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.