Collaborative Research: Understanding the causes of Atlantic hurricane variability in the late Holocene

由于观测数据集的简短和不完整，人们对北大西洋西部边缘强飓风风险的时空格局知之甚少。为了了解这种风险在空间和时间上是如何变化的，并在几十年到百年的时间尺度上探索这种风险变化的潜在驱动因素，我们需要通过使用强烈飓风登陆的代理记录来扩展我们的观察。沿海天坑和蓝洞（淹没的天坑）中保存的粗粒度飓风诱发的事件床提供了许多世纪前强烈飓风通过的档案。该项目的重点是在北大西洋西部的一系列地点重建强烈飓风袭击。这些重建将提供过去两千年来在大范围气候条件下强烈飓风频率的详细地点特定信息，为评估当前和未来的风险提供重要的基线。基于高沉积速率的深海岸沉积物中心的粗粒度事件层沉积物重建强烈飓风袭击，提供了这些事件的长期档案，可追溯到数百年至数千年。这些事件的仪器记录非常有限，既不足以确定在百年或更长时间尺度上影响风暴活动的气候成分，也无法解决与仪器周期不同的气候制度下的飓风-气候相互作用。令人担忧的是，代理记录提供的证据表明，在过去两千年中，历史上前所未有的强烈飓风活动影响了美国东海岸和墨西哥湾沿岸。确定过去飓风活动的时空格局以及造成这种前所未有的强烈登陆的气候强迫机制，对于评估未来社会面临的风险至关重要。该项目将在北大西洋西部地区增加8个新的重建项目，以填补目前可用的高分辨率飓风重建网络在过去一千年或更长时间内的关键空间空白。除了将新的沉积物代用记录添加到更大的现有数据库之外，研究小组还将重新访问三个地点（大巴哈马群岛、凯科斯群岛和萨尔岛），这些地点在马修飓风和厄玛飓风进行现场采样后遭到袭击。这些强烈飓风对已经有岩心的野外遗址的袭击提供了一个难得的机会，可以用现代的类似物来校准手头的古档案。扩大后的站点网络将用于评估飓风活动的时空变化。由此产生的飓风年表数据库，结合对新的和现有的但未经分析的模式模拟的分析，可以用来增强我们对控制强烈飓风活动的基本过程的理解。作为该项目的一部分，研究生将接受实验室技术、实地工作和数据分析方面的培训。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The spatial and temporal patterns of intense-hurricane risk along the western North Atlantic margin are poorly known due to the brevity and incompleteness of observational datasets. In order to understand how this risk may change in space and time, and explore the potential drivers of changes in that risk on multidecadal to centennial timescales, we need to extend our observations by employing proxy records of intense hurricane landfalls. Coarse-grained hurricane-induced event beds preserved in coastal sinkholes and blue holes (submerged sinkholes) provide an archive of intense hurricane passage that extends back many centuries. This project focuses on developing reconstructions of intense-hurricane strikes at a series of sites across the western North Atlantic. These reconstructions will provide detailed site-specific information of intense hurricane frequency across a wide range of climate conditions over the last two millennia, providing an important baseline for assessing current and future risk.Reconstructions of intense-hurricane strikes based on coarse-grained event bed deposits in deep coastal sediment depocenters with high-deposition rates provide long term archives of these events dating back hundreds to thousands of years. The instrumental record of these events is very limited and is neither sufficient for identifying the components of climate that influence storm activity on centennial and longer timescales, nor capable of resolving hurricane-climate interactions during climate regimes not analogous to the instrumental period. Alarmingly, proxy records provide evidence that historically unprecedented levels of intense-hurricane activity impacted the eastern seaboard and Gulf coasts of the USA during the last two millennia. Determining the spatial and temporal pattern of past hurricane activity and the climatic forcing mechanisms responsible for this unprecedented level of intense landfalls is critical for assessing the future risks facing society. This project will add eight new reconstructions from sites across the western North Atlantic that fill critical spatial gaps in the currently available network of high-resolution hurricane reconstructions spanning the last millennium or more. In addition to adding new sediment proxy records to the larger existing database, the research team will revisit three locations (Grand Bahama, Caicos and Cay Sal) that were struck after field sampling by Hurricanes Matthew and Irma. These strikes by intense hurricanes at field sites already cored offer a rare opportunity to calibrate the paleo archives in hand with modern analogs. The expanded network of sites will be used to assess spatial and temporal changes in hurricane activity. The resulting database of hurricane chronologies, in combination with analysis of new and existing but unanalyzed model simulations, can be used to enhance our understanding of the fundamental processes governing intense hurricane activity. As part of this project, a graduate student will receive training in laboratory techniques, field work and data analysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.