Collaborative Research: Developing a high-resolution late Holocene sediment record of rapid Arctic climate change from the Beaufort Sea coastal zone

PI建议开发一个新的，高分辨率（每年到近十年）的古气候记录（0至~2,000年），从沉积物芯采取的北极泻湖设置相邻的河流排入博福特海。这项工作是EAGER奖的后续行动，该奖项允许在2010年8月在科尔维尔三角洲附近的辛普森泻湖收集初始岩心材料和地震数据集。初步结果表明，这些沉积物岩心包含了邻近大陆对气候变化的系统响应的宝贵历史（例如，河流流域）和陆地-海洋联系。将对所有岩心进行地层学（X射线照相）、整体有机和矿物含量、粒度测定和地质年代学（239，240 Pu/137 Cs）分析。将对古气候代用指标进行详细分析：将使用放射性碳确定这些岩心较深部分的年龄-深度关系。将采用的气候指标是有机生物标志物（木质素-酚、木糠、植物色素和碳同位素）和矿物示踪剂（主要和微量元素化学、稳定同位素、粘土矿物学、重矿物组合、粒度测定法、事件层地层学）。中心假设是，泻湖设置在博福特海包含高质量的沉积物记录，因为他们收到的沉积物输入从较大的河流排水的布鲁克斯范围，如果开发，将大大提高我们的知识在过去的两个千年高北极古气候。PI假设了三个不同的来源：1）排出布鲁克斯山脉和北极海岸平原（ACP）的河流，2）侵蚀海岸线永久冻结ACP沉积物和过度冲洗屏障岛屿的风暴，以及3）浮游植物，冰藻和底栖生物的海洋初级生产。在对最近的事件层（年度和风暴沉积物）矿物和POC继承进行初步微尺度检查后，解释古气候引起的成分波动是必要的，他们将检查层中时间变化的底层记录，对比场地以解耦源的空间变化。由于三个源端元具有不同的矿物/POC组成，他们认为时间变化将提供有关影响其通量大小的气候变化的替代信息，包括1）陆地固定冰范围，2）冰川高地的河流沉积物供应，3）永久冻土融化，4）夏季-秋季风暴，5）沿海初级生产力。注意到北极在世纪后半叶发生的迅速变化，联邦机构间北极环境变化研究（北极变化）计划已经提出了确定北极最近和正在发生的气候变化在多大程度上可以归因于人为强迫的需要。 一个成功的项目将有助于回答这个问题。

The PIs propose to develop a new, high-resolution (annual to subdecadal) paleoclimate record (0 to ~2,000 y) from sediment cores taken in Arctic lagoonal settings adjacent to rivers emptying into the Beaufort Sea. This effort is a follow-up to an EAGER award that allowed collection of initial core material and a seismic dataset in Simpson Lagoon near the Colville River delta in August 2010. Initial results suggest that these sediment cores contain a valuable history of system response to climate change on the adjacent continent (e.g., river drainage basins) and terrestrial-marine linkages. All cores will be analyzed for stratigraphy (X-radiography), bulk organic and mineral content, granulometry, and geochronology (239,240Pu/137Cs). Detailed analysis for paleoclimate proxies will be carried out: the age-depth relationship for the deeper part of these cores will be determined using radiocarbon. Climate indicators that will be applied are organic biomarkers (lignin-phenols, cutins, plant pigments, and ä13C) and mineral tracers (major and trace element chemistry, stable isotopes, clay mineralogy, heavy mineral assemblages, granulometry, event-layer stratigraphy). The central hypothesis is that lagoonal settings within the Beaufort Sea contain high quality sediment records because they receive sediment input from larger rivers that drain the Brooks Range, that, if exploited, will dramatically improve our knowledge of high Arctic paleoclimate over the last two millenia. The PIs hypothesize three distinct sources: 1) rivers that drain the Brooks Range and the Arctic Coastal Plain (ACP), 2) storms that erode shoreline permafrosted ACP deposits and overwash barrier islands, and 3) marine primary production by phytoplankton, ice algae, and benthos. After an initial micro-scale examination of recent event layer (annual and storm deposits) mineral and POC succession, necessary to interpret paleoclimate-induced fluctuations in composition, they will examine the downcore record of temporal variations in layers, contrasting sites to decouple spatial changes in sources. Since the three source end-members have distinct mineral/POC composition, they believe that temporal variations will provide proxy information about climate changes that influence their flux magnitude including 1) landfast ice extent, 2) river sediment supply from the glaciated uplands, 3) permafrost thawing, 4) summer-fall storminess, and 5) coastal primary productivity.Noting the rapid changes that have occurred in the Arctic during the latter half of the 20th century, the federal interagency Study of Environmental Arctic Change (SEARCH) program has cited the need to determine to what extent recent and ongoing climate changes in the Arctic can be attributed to anthropogenic forcing. A successful project will contribute to answering that question.