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

PIs建议开发一种新的，高分辨率的（年至年代际）古气候记录（0至~ 2000年），这些记录来自于流入波弗特海的河流附近的北极泻湖环境的沉积物岩心。这项工作是继2010年8月在科尔维尔河三角洲附近的辛普森泻湖收集初始核心材料和地震数据集之后的又一成果。初步结果表明，这些沉积物岩心包含了对邻近大陆（如河流流域）气候变化系统响应和陆海联系的宝贵历史。将对所有岩心进行地层学（x射线照相）、总体有机和矿物含量、粒度测定和地质年代学（239,240Pu/137Cs）分析。将对古气候代用物进行详细分析：这些岩心较深部分的年龄-深度关系将使用放射性碳测定。将应用的气候指标是有机生物标志物（木质素酚类物质、切屑、植物色素和ä13C）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、事件层地层学）。核心假设是，波弗特海内的泻湖环境包含高质量的沉积物记录，因为它们从排干布鲁克斯山脉的大河中吸收沉积物，如果加以利用，将极大地提高我们对过去两千年来北极高纬度古气候的认识。PIs假设了三个不同的来源：1)排干布鲁克斯山脉和北极海岸平原（ACP）的河流；2)侵蚀海岸线永久冻土ACP沉积物和冲过屏障岛的风暴；3)浮游植物、冰藻和底栖动物的海洋初级生产。在对解释古气候引起的成分波动所必需的近期事件层（年沉积和风暴沉积）矿物和POC演替进行初步的微观尺度检查之后，他们将检查下层时间变化的记录，对比不同地点以解耦源的空间变化。由于三个源端成员具有不同的矿物/POC组成，他们认为时间变化将提供影响其通量大小的气候变化的代理信息，包括1)陆地冰范围，2)冰川高地的河流沉积物供应，3)永久冻土融化，4)夏秋风暴，以及5)沿海初级生产力。联邦机构间北极环境变化研究（SEARCH）计划注意到20世纪下半叶北极地区发生的快速变化，指出有必要确定北极地区最近和正在发生的气候变化在多大程度上可归因于人为强迫。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.