Integrating novel molecular techniques to disentangle the roles of climate, time, and human agency on the evolution of the Icelandic landscape

项目摘要非技术描述：随着北极继续以高于全球平均水平的速度变暖，我们预测生态系统将如何响应和景观将如何变化的能力仍存在重大不确定性。我们可以看看最近地球历史上的温暖时期，以更好地约束地球系统将如何应对未来一个世纪的变暖。在最后一个冰河时代结束时，地球的轨道是这样的，北半球在夏季接收到的太阳能比现在多近10%。这些额外的能量足以融化冰岛几乎所有的冰川，萨迦夫妇说，白桦林从海岸一直延伸到山区。在过去的12000年里，冰岛湖泊和附近的复合土壤中的沉积物中含有跟踪温度、干旱和植被历史变化的分子化合物。这些“代理”提供了一种方法，可以准确地重建自上一个冰河时代结束以来冰岛各地气候和生态系统状况的连续历史。这项研究得益于沉积档案中DNA的恢复和有机地球化学的最新进展，以分离跟踪温度和水分平衡的生物标志物。当代冰岛景观的一个普遍特征是广泛的土壤侵蚀，但这种侵蚀是人类定居和畜牧活动还是气候变化的结果仍然存在争议。在年代久远的湖泊沉积物中保存的与土壤侵蚀有关的地球化学代用物旨在解开气候和人类在冰岛土壤侵蚀历史中的作用。该项目有助于启动一个早期职业生涯的拉丁裔科学家，为挪威DNA实验室最近的博士后博士提供国际机会，并支持一个新的博士生，以及支持和指导有动力的本科生，他们在一个高度相关的领域获得研究经验。有了一名嵌入式记者，将这项研究得出的气候变化的潜在影响传播给更广泛的公众就得到了加强。技术描述：北极目前的变暖速度是全球平均速度的两倍，预计到2100年，夏季气温将比20世纪末的平均气温高出4到6摄氏度。北极变暖加剧预计将导致木本植物向北迁移。木本植被的增加将降低地表反照率并增加大气水蒸气，这是目前气候模式中缺乏约束的正反馈机制。在冰岛，分层的、年代可靠的湖泊沉积物记录跨越了当前的间冰期（全新世），包含了丰富的沉积古DNA （sedaDNA）和温度（brGDGTs）、水文（delta2-Hwax）和人类（粪便固醇和多环芳烃）的脂质生物标志物代用物。对现代土壤和湖泊表层沉积物网络的分析将提供校准，增强社区对这些有前途的新分子代用物的理解，并促进区域训练集的发展。将局部校准与湖底沉积物和分层风成岩的类似测量相结合，将能够可靠地重建过去的生态系统及其对夏季温度和水文气候的依赖。这些数据集的新整合将为以下问题提供革命性的新见解：1)冰岛全新世早期相对于今天的温度有多高；2)在全新世早期温暖时期，木本植物在什么时候以及在什么高度上建立起来；3)气候、火山活动和/或挪威人定居在多大程度上导致了今天冰岛大地上普遍存在的土壤侵蚀。该项目的预期结果提供了关键数据集，为政策提供信息，并改善对北极迅速变暖的预测。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。

Project AbstractNon-Technical Description:Significant uncertainties remain in our ability to predict how ecosystems will respond and landscapes will change as the Arctic continues to warm faster than the global average. We can look to past warm times in recent Earth history to better constrain how the Earth system will respond to warming over the coming century. At the end of the last ice age Earth's orbit was such that the Northern Hemisphere received nearly 10% more solar energy in summer than at present. That extra energy was sufficient to melt almost all Iceland's glaciers, and the Sagas say birch forests extended from the shores to the mountains. Molecular compounds that track changes in temperature, aridity, and vegetation history are contained within the sediment deposited in Icelandic lakes and nearby composite soils over the past 12,000 years. These "proxies" provide a means to accurately reconstruct a continuous history of climate and ecosystem status across Iceland since the end of the last ice age. This research benefits from recent advances in the recovery of DNA from sedimentary archives and in organic geochemistry to isolate biomarkers that track temperature and moisture balance. A pervasive feature of the contemporary Icelandic landscape is widespread soil erosion, but whether that erosion is a result of human settlement and pastoral activity or climate change remains debated. Geochemical proxies related to soil erosion preserved in well-dated lake sediment are targeted to disentangle the roles of climate and humans in Iceland's soil erosion history. This project helps launch an early-career Latino scientist, provides international exposure to a recent PhD as postdoc in a DNA laboratory in Norway, and supports a new PhD student, as well as supporting and mentoring motivated undergraduate students, who gain research experience in a highly relevant field. With an embedded journalist communicating the potential effects of climate change derived from this research to the wider public is enhanced. Technical Description:The Arctic is currently warming twice as fast as the global average with summer temperatures predicted to be 4 to 6 degrees C above late 20th Century averages by the year 2100. Amplified warming in the Arctic is expected to result in a northward shift in woody plants. The increase in woody vegetation will reduce surface albedo and increase atmospheric water vapor, positive feedback mechanisms that are currently poorly constrained in climate models. In Iceland, stratified, securely-dated, lake sediment records span the current interglacial (Holocene) and contain a rich archive of sedimentary ancient DNA (sedaDNA) and lipid biomarker proxies for temperature (brGDGTs), hydrology (delta2-Hwax) and human agency (fecal sterols and PAHs). The analysis of modern soil and lake surface sediment networks will provide calibrations that enhance the community's understanding of these promising new molecular proxies and facilitate the development of regional training sets. Merging the local calibrations with similar measurements downcore in lake sediment and stratified aeolianites will enable reliable reconstructions of past ecosystems and their dependence on summer temperature and hydroclimate. The novel integration of these datasets will provide transformative new insights into 1) how much warmer was the early Holocene in Iceland relative to today, 2) when and to what elevation woody plants established themselves during early Holocene warmth, and 3) to what extent climate, volcanism and/or Norse settlement led to the widespread soil erosion apparent across the Icelandic landscape today. Anticipated results from this project provide key datasets needed to inform policy and improve forecasts of a rapidly warming Arctic.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.