Collaborative Research: Unraveling North American Ice-Sheet Dynamics and Regional Sea-Level Change along the U.S. Mid-Atlantic over the Last Glacial Cycle

海平面上升对世界各地的沿海生态系统和社区产生了影响。影响局部海平面上升的最重要因素之一是陆地表面的垂直运动。这些调整可能是由冰川和冰盖的消长造成的，这些冰川和冰盖通常位于数千公里之外。更好地理解这种冰川-陆地相互作用--被称为冰川均衡调整--可以改善对未来海平面上升的预测。这项研究将绘制弗吉尼亚州东海岸形成于过去约12万年的海岸线沉积物的地图并确定其日期。重点放在海平面接近或高于目前水平的时候。这些数据将为冰川均衡调整和冰盖变化的建模提供信息，以更好地量化全球冰盖消长的历史。这项研究将解决有关过去冰川时期区域海平面和冰盖变化的问题。这项工作还可能改进对未来冰川均衡调整对区域海平面上升影响的预测。此外，该项目还将支持科学家与位于弗吉尼亚州马奇庞戈的非营利性组织巴里岛中心之间的合作。这次合作将把科学团队的地质成果与该地区的当地社区知识结合起来。这项工作将开发博物馆展品，重点是弗吉尼亚州东海岸的地质和自然历史。上一次冰川周期的全球冰量变化是冰期气候变化的直接和敏感的衡量标准。然而，区域(相对)海平面受控于一系列局部因素，其中最主要的是冰川均衡调整。上一次冰川周期期间海平面变化历史上的重大不确定性--以及冰川均衡调整在其中的作用--突显了在整个冰盖增长阶段(12万至26000年前)需要高质量和年代准确的海平面标记物。中场海平面观测(沿冰盖外围隆起)有可能弥合全球海平面和当地大陆冰盖行为之间的理解差距，因为这些位置的相对海平面对附近冰盖的体积和范围的变化以及全球平均海平面变化很敏感。这项研究将聚焦于美国弗吉尼亚州的中场东海岸，首先分析高分辨率的地形和地下测绘数据，赋予相关的被保存的更新世海岸沉积物指示性意义，并开发一个全面的地质年代学，以创建在最后一次冰盖生长期间强有力的当地中场海平面记录。然后，我们将使用一系列可能的冰载历史来执行最先进的海平面模拟，这些历史跨越全球平均海平面和冰盖几何的不确定性范围，以便深入了解北美冰盖在这段时间内的动态。通过这样做，这项研究将更好地量化全球冰盖消长的历史，并更好地了解气候强迫和冰盖动力学之间的联系，以及对全球海平面和中场相对海平面的相关影响。此外，这项工作将支持两名博士生和一名职业早期PI的职业发展，并指导两个本科生研究项目。该项目将与非营利性的巴里尔群岛中心合作，吸引当地社区分享经验知识，以帮助创建博物馆展览。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Rising sea levels impact coastal ecosystems and communities around the world. One of the most important factors influencing sea level rise locally is the vertical movement of the land surface. These adjustments can be caused by the growth and decay of glaciers and ice sheets which are often located thousands of kilometers away. A better understanding of this ice-land interaction—termed glacial isostatic adjustment—can improve predictions of future sea-level rise. This study will map and date shoreline deposits along the Eastern Shore of Virginia that were formed over the last ~120,000 years. The focus is on times when sea level was near to, or higher than present. These data will inform modeling of glacial isostatic adjustment and ice-sheet changes to better quantify the history of global ice sheet growth and decay. This research will address questions surrounding past regional sea-level and ice-sheet changes over the last glacial period. The work may also improve projections of the effect of glacial isostatic adjustment on regional sea-level rise into the future. Additionally, this project will support collaboration between the scientists and the non-profit Barrier Islands Center in Machipongo, Virginia. The collaboration will combine the geological results from the science team with local community knowledge of the region. This work will develop museum exhibits focused on the geology and physical history of the Virginia Eastern Shore. Global variations in ice volume through the last glacial cycle are a direct and sensitive measure of ice age climate change. However, regional (relative) sea level is controlled by a suite of local factors, primary among which is glacial isostatic adjustment. Significant uncertainty in the history of sea-level changes during the last glacial cycle—and the role of glacial isostatic adjustment in those—highlights the need for high-quality and well-dated sea-level markers across the ice-sheet growth phase (120,000 to 26,000 years ago). Mid-field sea-level observations (along the peripheral bulge of ice sheets) have the potential to bridge gaps in understanding between global sea level and local continental ice-sheet behavior, since relative sea level at these locations is sensitive to changes in the volume and extent in nearby ice sheets, as well as globally averaged sea-level changes. Focusing on the mid-field Eastern Shore of Virginia (USA), this study will first analyze high-resolution topographic and subsurface mapping data, assign indicative meanings to associated preserved Pleistocene coastal deposits, and develop a comprehensive geochronology to create a robust local, mid-field sea-level record over the period of growth of the last ice sheet. We will then perform state-of-the-art sea-level simulations using a range of possible ice-loading histories, which span the range of uncertainty on global mean sea level and ice-sheet geometries in order to gain insight into North American ice-sheet dynamics over this time period. In doing so, this study will better quantify the history of global ice sheet growth and decay and improve understanding of linkages between climate forcings and ice-sheet dynamics, with associated impacts on global eustatic, and mid-field relative sea level. Furthermore, this work will support the career development of 2 PhD students and an early-career PI, and mentor two undergraduate student research projects. The project will enable a collaboration with the non-profit Barrier Islands Center to engage the local community to share experiential knowledge to help create a museum exhibit.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.