Collaborative Research: Volcanism in the Arctic SysTem (VAST): Geochronology and Climate

该项目整合了建模和古环境数据，以更好地了解火山活动在北极系统中的作用，并更好地利用广泛的火山灰层来确定日期，并同步整个北极的古环境记录。北极包括北大西洋和北太平洋地区的主要火山活动中心。来自北极或热带火山活动的平流层气溶胶改变了北极的辐射平衡，进而影响大气环流，产生全球性后果。夏季日照减少可能导致北极持续几年的大幅冷却，但如果系统通过阈值条件，这些扰动可能会产生更长的影响，因此强烈的正反馈会导致北极系统状态的变化。新的古数据表明，在过去的千年里，在向小冰河时代过渡期间，加拿大北极地区陆地冰盖持续了几个世纪，在两次最大的火山爆发之后，冰盖急剧增加。爆炸性的北极火山作用可以产生大量的源和时间诊断火山灰，具有广泛的分布。这些火山灰层提供了时间同步的标志层，限制了古环境记录的地质年代学，并用于精确地同步来自湖泊，海洋和冰盖档案的记录，因此，可以更好地评估气候系统的超前和滞后。一个国际研究小组已经组建，通过气候模拟评估北极和热带火山爆发对北极系统的影响，在整个北大西洋北极地区的古环境研究中优化火山岩的效用。这是美国的贡献。这一努力的具体目标包括：-建立一个标准化的地球化学清单冰岛标志火山喷发在过去12,000年，并制定标准，以区分冰岛和北太平洋火山喷发。改进从沉积档案中识别和提取微火山灰的技术。将近端冰岛火山灰地球化学指纹扩展到远端湖泊，海洋和格陵兰冰芯档案中的microtephra。为大多数主要的冰岛火山爆发绘制羽流轨迹的通用地图。通过气候建模和模型输出与古环境重建的比较，评估北极系统对高纬度和低纬度火山爆发的敏感性。

This project integrates modeling and paleoenvironmental data to obtain a better understanding of the role of volcanism in the Arctic System, and to better utilize widespread tephra layers to date and synchronize paleoenvironmental records across the Arctic.The Arctic includes major centers of volcanism in the North Atlantic and the North Pacific sectors. Stratospheric aerosols derived from either Arctic or tropical volcanism alter the radiative balance of the Arctic, which in turn influences atmospheric circulation with global consequences. Reduced summer insolation can lead to substantial Arctic cooling of a few years' duration, but these perturbations may produce longer impacts if the system passes through a threshold condition, whereby strong positive feedbacks yield changes in the state of the Arctic System. New paleodata suggest that dramatic increases in terrestrial ice caps in Arctic Canada lasting several centuries occurred following two of the largest eruptions of the past millennium, during the transition into the Little Ice Age. Explosive Arctic volcanism can produce large volumes of source- and time-diagnostic tephra, with extensive distributions. These tephra layers provide time-synchronous marker horizons that constrain the geochronology of paleoenvironmental records and serve to precisely synchronize records derived from lacustrine, marine, and ice-sheet archives, thereby allowing a better assessment of leads and lags in the climate system.An international research team has been assembled to assess the impact of both Arctic and tropical eruptions on the Arctic System through climate modeling and to optimize the utility of tephras in paleoenvironmental studies throughout the North Atlantic Arctic. This represents the US contribution. Specific objectives of this effort include:- Establish a standardized geochemical inventory of Icelandic marker tephra erupted over the past 12,000 years, and develop criteria to differentiate Icelandic from North Pacific tephra.- Improve techniques to identify and extract microtephra from sedimentary archives.- Extend proximal-derived Icelandic tephra geochemical fingerprinting to microtephra in distal lacustrine, marine and Greenland ice-core archives.- Develop generalized maps of plume trajectories for most major Icelandic eruptions.- Evaluate the sensitivity of the Arctic System to high- and low-latitude eruptions through climate modeling and comparisons of model output to paleoenvironmental reconstructions.