Collaborative Research RUI: Decadal cyclicity in NAO proxies from northwest Iceland lake sediments

这项为期四年、现场和实验室密集的工作将古北大西洋涛动(NAO)的记录扩展到2000年前，基于现有的古海平面数据，包括花粉、有机和无机化学、矿物磁性和颗粒大小，这些数据表明与冰岛的NAO活动有很强的定性联系。它利用来自当前沉积环境的分水岭土壤和湖泊沉积物的校准数据集，从冰岛西北部过去2000年的湖泊、土壤和河流沉积物中与NAO建立了新的定量联系。它确定了造成冰岛湖泊矿物沉积独特的80-100年周期的具体环境机制，并检验了这些假设：1.冰岛暴雨和降水加剧的时期，例如发生在NAO指数高和正的时候，持续和可预测地从分水岭土壤储备中动员矿物质，改变湖泊水特征，形成独特的湖泊沉积物沉积。与人类占领和土地利用有关的分水岭干扰增加了十年周期的幅度和/或重现间隔；在过去的30年里，对湖泊流域的保护已经导致了一种优先占领状态的趋势，正如湖泊沉积物地球化学所记录的那样。更广泛的影响北大西洋涛动(NAO)是主导北半球大气条件的全球尺度环流模式的一部分。它与北美、欧洲和中东的干旱、洪水和恶劣天气模式有关。先前的工作表明，NAO经历了规律的周期，扰乱了分水岭的土壤，改变了流入湖泊和河流的营养物质，至少在冰岛是这样。这项研究利用湖泊效应“观察”了过去2000年，并确定了NAO最活跃的时间。由于人类对冰岛的占领始于1000多年前，而且这个项目产生了过去2000年的变化记录，它提供了一个独特的视角，展示了人类在放大与NAO相关的气候变化对脆弱地貌的影响方面所起的作用，例如冰岛和许多其他以前的冰川地区发生的影响。通过评估流域在人类土地利用前后以及保护管理之前和之后对重复的气候干扰(如NAO)的反应，这项工作提供了关于保护努力在缓解气候变化的人类方面的有用性的见解。该项目还为研究机会相对有限的机构(普利茅斯州立大学和塞勒姆州立学院)的本科生和研究生提供急需的研究、教育、实地和实验室培训机会，提供与三个一级研究机构(缅因州大学、科罗拉多州大学和明尼苏达州大学)的接触和接触。学生们参与到项目的各个层面，学习最先进的跨学科方法，通常是在以研究为导向的机构中实践的。它为学生创造机会，让他们在口头和书面出版物中交流与研究成果相关的复杂想法。参与该项目的五名高级研究人员还接受了最先进的跨学科方法和应用方面的培训，这提高了他们的教学和研究能力。这项工作涉及大量使用LacCore和大湖观测站的国家实验室设施，并结合新英格兰3个校区的努力，利用现有设施和人力资源，建设新的区域能力。

Technical DescriptionThis four-year, field- and lab-intensive work extends the paleo-North Atlantic Oscillation (NAO) record to 2000 years BP, building on existing paleolimnological datasets of pollen, organic and inorganic chemistry, mineral magnetism and particle-size that show strong qualitative linkages with NAO activity on Iceland. It develops new quantitative linkages with the NAO from these same proxies in northwest Iceland lake, soil and stream deposits of the last 2000 years, using calibration datasets of watershed soil and lake sediments derived from current depositional environments. It identifies the specific environmental mechanisms responsible for creating distinct, 80-100 year cycles in the mineral deposits of Icelandic lakes and tests these hypotheses:1. periods of intensified storminess and precipitation on Iceland, such as occur when the NAO index is high and positive, consistently and predictably mobilize minerals from watershed soil reserves and alter lake water characteristics to form distinctive lake sediment deposits, and2. watershed disturbances related to human occupation and land-use increase the amplitude and/or recurrence interval of the decadal cycle, and3. conservation protection of the lakes' watersheds in the last 30 years has resulted in a trend towards that of a pre-occupation state, as documented in the lake sediment geochemistry.Broader impactThe North Atlantic Oscillation (NAO) is part of a global-scale circulation pattern that dominates Northern Hemisphere atmospheric conditions. It is linked to patterns of drought, flooding and severe weather in North America, Europe and the Middle-East. Prior work has shown that the NAO undergoes regular cycles that disturb watershed soils and alter nutrient inflows to lakes and rivers, at least on Iceland. This works uses that lake effect to "see" into the past 2000 years and identify when the NAO was most active. Because human occupation of Iceland began just over 1000 years ago, and this project produces records of change covering the last 2000 years, it offers a unique look at the human role in magnifying the impacts of NAO-related climate changes on fragile landscapes, such as occur in Iceland and in many other previously glaciated regions. By assessing the response of watersheds to repeated climate disturbances, like the NAO, before and after human land use and before and after conservation management, this work provides insight on the usefulness of conservation efforts in mitigating human aspects of climate change. This project also provides much needed research, education, field and laboratory training opportunities for undergraduate and graduate students at institutions with relatively limited research opportunities (Plymouth State University and Salem State College), providing access and engagement with three tier-one, research institutions (U. Maine, U. Colorado and U. Minnesota). Students are involved at every level of the project and learn state-of-the-art interdisciplinary approaches typically practiced at research-oriented institutions. It creates opportunities for students to communicate complex ideas associated with research findings in oral and written publications. The five senior researchers involved in this project also receive training in state-of-the-art cross-disciplinary approaches and applications, which enhances their teaching and research capabilities. This work involves significant use of National Laboratory facilities at LacCore and Large Lakes Observatory and combines efforts of 3 New England campuses, leveraging existing facilities and human resources and building new regional capacity.