Collaborative Research: Climatic Instability in Interior Alaska from the isotopic record of Late Quaternary ground ice

摘要：14c年代冰缘冰楔生长间隔和d18O剖面的初步结果表明，阿拉斯加北极地区末次冰期气候具有千年尺度的变率特征。这些突发事件的特征是在距今45000年到20000年之间，冰楔交替生长和至少7次解冻期。冰楔d18O值随冰期减小而减小，表明在寒冷的气候条件下逐渐变冷。评估了这些千年尺度的冰楔生长/融化事件是北半球冰川和格陵兰冰中9个温暖的Dansgaard/Oeschger事件（冰川3-11）的北极表现的假设。为了验证这一假设，将通过捕获的有机物质的14C来确定冰楔的年代，并通过生成d18O和dD时间序列来估计古气候条件，d18O和dD时间序列是冬季气温的代表。如果这一假设是正确的，这将表明在格陵兰岛和北大西洋周围强烈表现的千年尺度突变和严重气候变化具有半球空间指纹，并突出了多年冻土区对全球气候变化在千年时间尺度上的敏感性。这项研究将利用在阿拉斯加费尔班克斯附近的CRREL永久冻土隧道中独特的地面冰记录，在控制和工程实验室（CRREL）的环境条件下，允许在冰点以下的温度下进行精确采样，并对沉积物和冰及其沉积和热历史进行详细而严格的分析。更广泛的影响：由于缺乏北极和永久冻土区的古气候数据，这项工作将记录北极气候对全球气候变化的敏感性。很少有来自北极环境的末次冰期数据可用于校准全球气候模式，从而限制了科学家预测与人为全球变暖相关的未来气候变化的能力。然而，全球变暖的影响已经在北极地区得到了记录，那里的土著文化、村庄和生活方式将受到大规模或快速气候变化的严重影响。冰楔和地面冰的详细稳定同位素分析将为北极无冰川地区提供一个高分辨率的替代数据源，填补了我们对全球气候中冰-海-气相互作用认识的重要数据空白。研究将是一项合作努力，支持达特茅斯学院和内华达大学拉斯维加斯分校的本科生和研究生。

ABSTRACTLawsonOPP-0714060Intellectual Merit : Preliminary results of 14C-dated periglacial ice wedge growth intervals and d18O profiles suggest that the last glacial climate in Arctic Alaska was characterized by millennial-scale variability. These abrupt events are characterized by alternating ice wedge growth and at least seven thaw periods over the interval of 45,000 to 20,000 yrs BP. A decrease in ice wedge d18O values with decreasing ice age indicates gradual cooling during cold stadial climates. The hypothesis that these millennial-scale ice-wedge growth/thaw events are arctic manifestations of northern hemisphere stadials and the nine warm Dansgaard/Oeschger events (stadials 3-11) evident in Greenland Ice is evaluated. To test the hypothesis, ice wedges will be dated by 14C of entrapped organic material, and paleoclimate conditions estimated via the generation of d18O and dD time series, a proxy for winter air temperature. If the hypothesis is correct, it will indicate that the abrupt and severe millennial-scale climate changes strongly manifested in Greenland and the circum-North Atlantic have a hemispheric spatial fingerprint, and highlight the sensitivity of permafrost areas to global climate change on millennial time scales. This research will utilize the unique ground ice record in the Quaternary age permafrost in the Cold Regions Research CRREL Permafrost Tunnel near Fairbanks, Alaska, under controlled and Engineering Lab (CRREL) environmental conditions that allow precise sampling in subfreezing temperatures linked to a detailed and rigorous analysis of the sediments and ice and their sedimentary and thermal history.Broader Impacts: Due to a paucity of paleoclimatic data from Arctic and permafrost regions, this work will document the sensitivity of Arctic climate to global climate changes. Few data from the last glacial period are available from Arctic environments to calibrate global climate models, thus limiting scientists' ability to predict future climate change associated with anthropogenic global warming. Yet the effects of global warming are already documented in Arctic regions where native cultures, villages and ways of life will be severely affected by large or rapid changes in climate. The detailed stable isotopic analyses of ice wedges and ground ice will provide a high resolution proxy data source for unglaciated regions of the Arctic, filling an important data gap in our understanding of ice-ocean-atmosphere interactions in global climate. Research will be a collaborative effort, supporting undergraduate and graduate students at Dartmouth College and University of Nevada-Las Vegas..