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。项目摘要：PI建议开发一个新的，高分辨率（每年到十年以下）的古气候记录（0 - 1000年）从北极内陆架的沉积物芯。该提案是北极自然科学小组定期提交的后续行动，该小组在审查期间受到批评，原因是：1）缺乏足够的数据来证实这种环境下的高质量古气候记录，2）鉴于没有联合国海洋和海洋法办事处的船只在北极高纬度地区工作，对后勤成功提出了质疑。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。研究员将在当地私人包租的研究船"Annika玛丽号"的一次巡航中从内大陆架收集沉积物岩心，该船目前定于2009年9月下旬（无冰期）在阿拉斯加博福特海岸的科尔维尔三角洲附近航行。在取芯之前，将收集辅助地震断面数据（海底下CHIRP和侧扫声纳），以确定该时间段沉积层积物保存最完好的记录。大约5至15个地点将被占用的大陆架和邻近的辛普森泻湖。所有岩心将在水深小于8米的地方潜水采集：短推岩心将用于获取高孔隙度的新近沉积层，较长的岩心（最长5米）将用潜水便携式振动器采集。将对所有岩心进行地层学（X射线照相）、大量有机物和矿物含量以及最近100至200年的地质年代学（使用210 Pb和137 Cs放射性示踪剂）分析。将从中选出两个岩心，对古气候代用指标进行详细分析：将使用AMS底栖有孔虫放射性碳测年法确定这些岩心较深部分的年龄-深度关系（5个/岩心）。将应用的气候指标是有机生物标志物（木质酚、植物色素和碳同位素）和矿物示踪剂（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，科尔维尔内大陆架含有高质量的沉积物记录，如果加以利用，将大大提高对过去几个世纪到一千年北极古气候的认识。他们认为，这个三角洲地区具有足够高的线性沉积物积累率（1厘米/年），可以保存气候变化引起的矿物和颗粒有机碳（POC）通量变化的季节性和年际记录，这些变化来自三个不同的来源。这些是1）排出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和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继承进行了初步的微尺度检查后，解释古气候引起的成分波动是必要的，他们建议检查层中时间变化的底层记录，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（融水）和沿海平原（永久冻土融化）输入的河流沉积物供应，3）夏季-秋季风暴和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.