Collaborative Research: Arctic Sensitivity to Climate Perturbations and a Millennial Perspective on Current Warming Derived from Shrinking Ice Caps

The goal of this proposal is to provide a millennial context for current warming and to better constrain the nature of abrupt climate changes over the past 5000 years in the North Atlantic sector of the Arctic. This goal will be addressed with
the powerful datasets derived from radiocarbon-dated vegetation preserved beneath ice caps for centuries to millennia, but now being exposed annually by current ice-margin retreat across northeastern Canada and West Greenland. These chronologies
define the pattern and timing of abrupt summer coolings in the recent past and place current warming in a millennial context. 14C dating of vegetation will be complemented by measuring in situ 14C inventories in recently exposed rock surfaces,
providing essential temporal constraints on the duration of ice-covered and ice-free conditions throughout the Holocene. Combined, these two datasets will provide the most secure evidence for the character of current summer warming by explicitly
dating when the region was last as warm as present. Comparing our climate reconstructions with on-going studies in NW Europe will help to separate the roles of unforced variability from hemispherically symmetric forcing as causes for abrupt climate
change. Research activities under this award will be made accessible to indigenous peoples by translating the goals and eventual results into Inuktitut, through posters that describe the research, and by offering public lectures in Iqaluit, the
capital of Nunavut, and at Qikiqtarjuaq, where INSTAAR has long had a presence. This research program will train a PhD and MSc student, and provides opportunities for undergraduate students to become involved with research, building on successful
traditions from previous years.

本项目的研究目标，是为当前的气候变暖提供千年尺度的背景参照，并更精准地限定北极北大西洋扇区过去5000年间突发性气候变化的本质特征。本研究将依托极具价值的数据集达成上述目标：该数据集源自保存在冰盖下数百年至数千年的经放射性碳定年的植被，而如今这些植被因加拿大东北部与西格陵兰地区当前的冰缘退缩，每年都得以裸露出来。这些年代序列能够明确近代突发性夏季降温的发生模式与时间节点，并将当前的气候变暖置于千年尺度的气候背景之中。针对植被的碳14定年，将辅以对新近裸露岩石表面的原位碳14储量测量，从而为全新世以来冰盖覆盖与无冰状态的持续时长提供关键的时间约束。将这两类数据集结合后，可通过精准测定该区域上一次达到当前温度水平的时间，为当前夏季变暖的特征提供最可靠的佐证。将本研究的气候重建结果与西北欧的现有研究进行对比，有助于区分突发性气候变化的两类驱动因素：未受强迫的气候变率与半球对称强迫作用。本项目的研究活动将面向原住民群体开放：通过将研究目标与最终成果翻译成因纽特语（Inuktitut）、制作介绍研究的海报，以及在努纳武特首府伊魁特与INSTAAR长期设有驻点的基吉柯塔鲁阿克举办公众讲座，让原住民群体了解本研究。本研究项目将培养一名博士生与一名硕士生，并依托过往的成功经验，为本科生提供参与科研工作的机会。