EAGER: Developing a high-resolution late Holocene sediment record of rapid Arctic climate change from the Colville delta and adjacent Beaufort Sea inner shelf

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。项目概述：PIs建议从北极内大陆架的沉积物岩心中开发一种新的高分辨率（年至次年代际）古气候记录（0- 1000年）。该提案是北极自然科学小组定期提交的后续报告，该报告在审查期间受到批评，原因是1)缺乏足够的数据来证实该环境下高质量的古气候记录，以及2)由于没有联合国北极行动中心的船只在北极高海拔地区工作，对后勤成功的质疑。如果没有这里提出的概念验证研究，这两个问题都无法解决。他们将在当地私人租用的研究船“安妮卡·玛丽号”（R/V Annika Marie）的一次巡航中收集内部冰架上的沉积物岩芯，目前计划于2009年9月下旬（无冰期）在阿拉斯加波弗特海岸的科尔维尔三角洲附近进行。在取心之前，将收集辅助地震样带数据（海底CHIRP和侧扫声纳），以定位该时间间隔沉积层状沉积物的最佳保存记录。大约5到15个地点将被占用在架子和邻近的辛普森泻湖上。所有岩心都将在水深不到8米的地方进行潜水采集：短岩心将用于回收高孔隙度的近期沉积层，而较长的岩心（高达5米）将使用潜水便携式振动器收集。所有岩心将进行地层学（x射线照相）、总体有机和矿物含量以及过去100至200年的地质年代学分析（使用210Pb和137Cs放射性示踪剂）。从这些岩心中选择两个岩心进行古气候代用物的详细分析：这些岩心较深处的年龄-深度关系将使用底栖有孔虫（5个/岩心）的AMS放射性碳定年法确定。将应用的气候指标是有机生物标志物（木质素酚、植物色素和ä13C）和矿物示踪剂（粘土矿物学、重矿物组合、粒度测定、事件层地层学）。π吗?核心假设是，科尔维尔内大陆架包含高质量的沉积物记录，如果加以利用，将极大地提高对过去几个世纪到一千年来北极高纬度古气候的认识。他们认为，这个三角洲地区具有足够高的线性沉积速率（1厘米/年），可以保存气候变化引起的矿物和颗粒有机碳（POC）从三个不同来源流向海底的季节性和年际记录。它们是：1)排干布鲁克斯山脉和北极海岸平原（ACP）的河流；2)ACP永久冻土沉积物的海岸侵蚀；3)浮游植物、冰藻和底栖生物的海洋初级生产。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演替进行了初步的微尺度检查之后，他们建议检查下层时间变化的记录，比较两个选定的地点，以解耦源的空间变化。由于三个端元源具有不同的矿物/POC组成，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（融水）和沿海平原（永久冻土融化）输入的河流沉积物供应，3)夏秋风暴和4)沿海地区的初级生产力。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Project Summary:The PIs propose to develop a new, high-resolution (annual to sub-decadal) paleoclimate record (0-1,000 y) from sediment cores taken on the Arctic inner continental shelf. The proposal is a follow-up to a regular Arctic Natural Sciences panel submission that was criticized during review due to 1) absence of adequate data to substantiate a high-quality paleoclimate record in this setting, and 2) questions about the logistical success in light of the absence of UNOLS vessels to work in the high Arctic. Neither issue can be addressed without a proof of concept study such as proposed here. The PIs will collect sediment cores from the inner shelf on one cruise of the R/V Annika Marie, a local and privately chartered research vessel, presently scheduled for late September 2009 (ice free period) adjacent to the Colville delta on the Beaufort Sea coast of Alaska. Ancillary seismic transect data (sub-bottom CHIRP and side-scan sonar) will be collected prior to coring to locate the best preserved record of depositionally laminated sediments of this time interval. About 5 to 15 sites will be occupied on the shelf and adjacent Simpson Lagoon. All cores will be diver-collected in less than 8 m water depth: short push cores will be used to retrieve the high-porosity recent sediment layers, and longer cores (up to 5 m) will be collected with a submersible portable vibracorer. All cores will be analyzed for stratigraphy (x-radiography), bulk organic and mineral content, and geochronology of the last 100 to 200 y (using 210Pb and 137Cs radiotracers). Two cores will be selected from these for detailed analysis of paleoclimate proxies: the age-depth relationship for the deeper part of these cores will be determined using AMS radiocarbon dating of benthic foraminifera (5/core). Climate indicators that will be applied are organic biomarkers (ligninphenols, plant pigments, and ä13C) and mineral tracers (clay mineralogy, heavy mineral assemblages, granulometry, event layer stratigraphy).The PIs? central hypothesis is that the Colville inner shelf contains a high quality sediment record, that, if exploited, will dramatically improve knowledge of high Arctic paleoclimate over the last centuries to a millennia. They believe this deltaic region has sufficiently high linear sediment accumulation rates (1 cm/y) to preserve a seasonal and interannual record of climate change-induced mineral and particulate organic carbon (POC) flux variations to the seafloor from three distinct sources. These are 1) rivers that drain the Brooks Range and the Arctic Coastal Plain (ACP), 2) coastal erosion of ACP permafrost deposits 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 propose to examine the downcore record of temporal variations in layers, comparing the two selected sites to decouple spatial changes in sources. Since the three end-member sources have distinct mineral/POC composition, temporal variations will provide proxy information about climate changes that influence their flux magnitude including 1) landfast ice extent, 2) river sediment supply from glacial (meltwater) and coastal plain (permafrost thawing) input, 3) summer-fall storminess and 4) primary productivity of the coastal zone.