Collaborative Research RUI: Decadal cycles in NAO proxies from northwest Iceland lake and soil sediments

技术描述这项为期四年的野外和实验室密集型工作将古北大西洋涛动（NAO）记录扩展到2000年BP，建立在现有的花粉、有机和无机化学、矿物磁性和颗粒大小的古湖泊学数据集上，这些数据集显示与冰岛NAO活动有很强的定性联系。它利用来自当前沉积环境的流域土壤和湖泊沉积物的校准数据集，利用冰岛西北部过去2000年的湖泊、土壤和河流沉积物的相同代用物，与NAO建立了新的定量联系。它确定了特定的环境机制，负责在冰岛湖泊的矿藏中创造独特的80-100年周期，并测试了这些假设：冰岛暴雨和降水加剧的时期，例如当NAO指数高且为正值时，持续和可预测地从流域土壤储备中调动矿物质，改变湖泊水特征，形成独特的湖泊沉积物；2 .与人类占用和土地利用有关的流域扰动增加了年代际循环的振幅和/或重现间隔；湖泊沉积物的地球化学特征表明，近30年来湖泊流域的保护工作导致了一种预先占领状态的趋势。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。先前的研究表明，至少在冰岛，NAO经历了有规律的循环，扰乱了分水岭土壤，改变了流入湖泊和河流的营养物质。这项工作利用湖泊效应“看到”过去2000年，并确定NAO最活跃的时间。由于人类对冰岛的占领始于1000多年前，而该项目产生了覆盖过去2000年的变化记录，因此它提供了一个独特的视角，以了解人类在放大与nao相关的气候变化对脆弱景观的影响方面所起的作用，例如在冰岛和许多其他以前的冰川地区发生的变化。通过评估流域在人类土地利用前后和保护管理前后对重复气候扰动（如NAO）的反应，本工作提供了对保护工作在减轻人类方面的气候变化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了急需的研究、教育、实地和实验室培训机会，提供了与三个一级研究机构（缅因大学、科罗拉多大学和明尼苏达大学）的接触和参与。学生参与项目的各个层面，并学习最先进的跨学科方法，通常在研究型机构中实践。它为学生在口头和书面出版物中交流与研究成果相关的复杂想法创造了机会。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的培训，以提高他们的教学和研究能力。这项工作涉及大量使用LacCore和大湖天文台的国家实验室设备，并结合三个新英格兰校区的努力，利用现有设施和人力资源，并建立新的区域能力。

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.