Collaborative Research: Volcanism in the Arctic System (VAST): geochronology and climate impacts

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苔藓层来确定和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。北极或热带火山作用产生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，造成全球后果。夏季日照减少可能导致北极持续数年的大幅降温，但如果系统超过阈值条件，这些扰动可能会产生更长的影响，从而产生强烈的正反馈，导致北极系统状态的变化。新的古数据表明，加拿大北极地区陆地冰盖的急剧增加持续了几个世纪，发生在过去千年中两次最大的喷发之后，也就是在过渡到小冰期期间。北极火山爆发可以产生大量具有来源和时间诊断意义的火山喷发，分布广泛。这些Tephra层提供了时间同步的标记层位，限制了古环境记录的地理年代学，并用于精确同步来自湖泊、海洋和冰盖档案的记录，从而能够更好地评估气候系统中的领先和滞后。已经组建了一个国际研究小组，通过气候模拟来评估北极和热带喷发对北极系统的影响，并优化冰盖在整个北大西洋北极古环境研究中的应用。这代表了美国的贡献。这项工作的具体目标包括：-建立冰岛过去12,000年来喷发的标志性火山喷发的标准化地球化学清单，并制定区分冰岛和北太平洋火山喷发的标准。-改进从沉积档案中识别和提取微火山喷发的技术。-将从近端提取的冰岛冰盖的地球化学指纹扩展到远湖、海洋和格陵兰冰芯档案中的微火山喷发。-为冰岛大多数主要喷发绘制羽流轨迹的通用地图。-通过气候模拟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喷发的敏感性。

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.