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》(公法111-5)资助的。项目摘要：私人投资机构提议从北极内大陆架上采集的沉积物岩芯开发一种新的高分辨率(每年到亚十年)古气候记录(0-1 000年)。该提案是对北极自然科学小组定期提交的意见的后续行动，该意见在审查期间受到批评，原因是1)缺乏足够的数据来证明这种环境下的高质量古气候记录，以及2)鉴于联东办事处没有船只在北极高地作业，后勤方面的成功受到了质疑。如果没有这里提出的概念研究的证明，这两个问题都不可能得到解决。PI将在R/V Annika Marie号的一次邮轮上从内陆架收集沉积物岩芯，这艘R/V Annika Marie是一艘当地和私人租用的科考船，目前计划于2009年9月下旬(无冰期)靠近阿拉斯加波弗特海海岸的科尔维尔三角洲。在取心之前，将收集辅助的地震横断面数据(海底声波和侧扫声纳)，以定位该时间段内保存最好的沉积层状沉积物记录。大约5到15个地点将被占据在大陆架和邻近的辛普森泻湖上。所有岩心将由潜水员在水深小于8米的地方采集：短推进岩芯将用于回收高孔隙度的新近沉积层，较长的岩芯(最长5米)将使用潜水式便携式振动器采集。将分析所有岩心的地层学(x射线照相术)、大量有机和矿物含量以及过去100至200年的地质年代学(使用210Pb和137Cs放射性示踪剂)。将从中选择两个岩心进行详细的古气候指标分析：这些岩心的深部年龄-深度关系将使用海底有孔虫的AMS放射性碳测年(5个/岩心)来确定。将应用的气候指标是有机生物标志物(木质素、植物色素和ä13C)和矿物示踪物(粘土矿物学、重矿物组合、粒度测量、事件层地层学)。中心假设是，科尔维尔内陆架包含高质量的沉积物记录，如果被开发，将极大地提高对过去几个世纪至数千年来北极高古气候的认识。他们认为，这个三角洲地区拥有足够高的线性沉积物积累速率(1厘米/年)，以保存气候变化导致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变化记录。这些河流1)排干布鲁克斯山脉和北极海岸平原(ACP)，2)海岸侵蚀ACP永久冻土沉积物，3)浮游植物、冰藻和底栖动物的海洋初级生产力。在对最近事件层(年度和风暴沉积)矿物和POC序列(解释古气候引起的成分波动)进行了初步的微观尺度检查后，他们建议检查下层时间变化的核心记录，比较选定的两个地点，以分离来源的空间变化。由于三个末端成员具有不同的矿物/POC组成，时间变化将提供影响其通量大小的气候变化的替代信息，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.