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

海平面上升影响着世界各地的沿海生态系统和社区。局部影响海平面上升的最重要因素之一是陆地表面的垂直运动。这些调整可能是由通常位于数千公里之外的冰川和冰盖的生长和衰变引起的。更好地了解这种被称为冰川均衡调整的冰陆相互作用，可以改善对未来海平面上升的预测。这项研究将绘制和确定弗吉尼亚东海岸海岸线沉积物的年代，这些沉积物形成于过去的12万年左右。重点是海平面接近或高于现在的时间。这些数据将为冰川均衡调整和冰盖变化的建模提供信息，从而更好地量化全球冰盖生长和衰减的历史。这项研究将解决围绕过去的区域海平面和冰盖变化在最后一个冰期的问题。这项工作还可以改进对未来冰川均衡调整对区域海平面上升影响的预估。此外，该项目将支持科学家与弗吉尼亚州马基蓬戈的非营利性屏障岛中心之间的合作。这项合作将把科学小组的地质结果与当地社区对该地区的了解结合起来。这项工作将发展以弗吉尼亚东海岸的地质和自然历史为重点的博物馆展览。末次冰期的全球冰量变化是对冰期气候变化的直接而敏感的测量。然而，区域（相对）海平面受一系列局地因素控制，其中主要是冰川均衡调整。在最后一个冰期的海平面变化历史中，存在着重大的不确定性——以及冰川均衡调整在其中所起的作用——这突出了在冰盖生长阶段（12万至2.6万年前）需要高质量的、年代准确的海平面标记物。由于这些地点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的变化都很敏感，因此，中间场海平面观测（沿着冰盖外围凸起处）有可能弥合对全球海平面和当地大陆冰盖行为之间的认识差距。本研究将重点关注美国弗吉尼亚州东部中部地区，首先分析高分辨率地形和地下测绘数据，为相关的保存的更新世沿海沉积物赋予指示意义，并开发一个全面的地质年代学，以创建一个强大的本地、中部地区海平面记录，记录最后一个冰盖的生长时期。然后，我们将使用一系列可能的冰负荷历史进行最先进的海平面模拟，这些历史跨越了全球平均海平面和冰盖几何形状的不确定性范围，以便深入了解这一时期北美冰盖的动态。这样，这项研究将更好地量化全球冰盖生长和衰减的历史，并提高对气候强迫和冰盖动力学之间的联系的理解，以及对全球海平面上升和中部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早期职业PI的职业发展，并指导两名本科生的研究项目。该项目将与非营利性的Barrier Islands Center合作，让当地社区分享经验知识，帮助创建一个博物馆展览。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。

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.