Last Interglacial sea-level evolution from U-series chronology of ooids, corals, and caves deposits from Crooked Island, Bahamas

海平面上升是最大的气候变化挑战之一。研究过去地球气候比今天温暖时海平面的变化有助于科学家预测到本世纪末及以后海平面可能上升多少。然而，未来海平面变化的幅度和速度仍然具有很大的不确定性。拟议的研究重点是129，000 - 116，000年前的末次间冰期，当时的平均气温比今天高约1.5 ° C。这一时期可能会为不久的将来海平面上升的模式提供独特的见解。该项目将把来自巴哈马的联合收割机实地和实验室数据与统计分析结合起来，以估计该地区末次间冰期的海平面。这些结果将反过来提高我们对末次间冰期全球海平面的认识。海平面的结果将有助于记录格陵兰岛和南极洲冰盖对过去气温升高的反应。冰盖的响应是预测未来几十年海平面变化的关键未知因素。因此，研究结果将具有很强的社会相关性。此外，这些结果将提供对过去海平面变化如何影响碳酸盐岛屿形成和演化的深入了解。 该项目的更广泛影响包括支持两名职业生涯初期的女科学家，并支持由其所在机构和美国自然历史博物馆主办的外联活动。末次间冰期期间全球平均海平面估计值似乎收敛于比现在高出6至9米的值。最近的观察和建模研究挑战了这一典型范围，表明值可能会显着降低。此外，冰融化的时间和来源仍然存在争议。该项目旨在通过测试和开发一种综合方法来减少末次间冰期全球平均海平面的不确定性，该方法将巴哈马克鲁克岛的四个海平面指标（珊瑚，卵囊，侧面边缘洞穴和地层环境）联系起来。这项研究将对铀系列年代学的ooids与详细的地层分析，以评估其沉积历史和派生的海平面位置。这项研究将使用垂直和水平背景作为相对时间，使用在同一沉积序列中沉积的珊瑚化石的U系列年龄作为绝对时间。该项目将记录丰富的侧翼边缘洞穴的海拔和时间，以提供对当地海平面历史的额外见解。这项研究将通过对冰川均衡调整和长期沉降的记录进行校正，将这些地方海平面观测结果转化为全球平均海平面。该项目涉及三个关键假设：末次间冰期期间全球平均海平面i）不超过5米，这一数值大大低于目前IPCC的共识; ii）可能在间冰期内振荡，这可能表明北方和南半球的冰融化是不同步的;和iii）没有超过每千年5米的最大速率，这表明冰盖对未来变暖的反应速度有多快或多慢。将在本研究中测试和开发的方法可以应用于地球仪上的其他碳酸盐岛屿，改善其他地点以及其他时间段的末次间冰期海平面重建。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Sea level rise is one of the greatest climate change challenges. Studies of how sea level has changed in past periods when Earth’s climate was warmer than today help scientists predict how much sea level may rise by the end of this century and beyond. However, the future magnitude and rate of sea level change are still highly uncertain. The proposed study focuses on the Last Interglacial period, 129,000-116,000 years ago, when temperatures were on average ~ 1.5 °C higher than today. This period may provide unique insights into the patterns of near future sea-level rise. This project will combine field and laboratory data from the Bahamas with statistical analysis to estimate Last Interglacial sea level in that region. Those results will in turn improve our understanding of global sea level during the Last Interglacial. The sea level results will help document the response of ice sheets in Greenland and Antarctica to elevated temperature in the past. The ice sheet response is a key unknown in efforts to predict sea-level changes in the coming decades. The study results will thus have strong societal relevance. In addition the results will provide insight into how past changes in sea level influenced the formation and evolution of carbonate islands. The broader impacts of the project include support for two early-career women scientists, and support for outreach activities hosted by their home institution and by the American Museum of Natural History. Global mean sea level estimates during the Last Interglacial appear to converge on values of 6 to 9 meters above present levels. Recent observational and modeling studies challenge this canonical range, suggesting values might be significantly lower. Moreover, the timing and source of ice melt that drove the high stand remains debated. This project aims to reduce the uncertainties of Last Interglacial global mean sea level by testing and developing a combined approach that links four sea level indicators (corals, ooids, flank margin caves, and stratigraphic context) from Crooked Island, Bahamas. The study will pair U-series chronology of ooids with detailed stratigraphic analysis to assess their depositional history and the derived sea level position. The study will use both vertical and horizontal context as relative timing, and U-series ages of fossil corals deposited in the same sedimentary succession as absolute timing. The project will document the elevation and timing of abundant flank margin caves to provide additional insight into the local sea level history. The study will translate these local sea level observations into global mean sea level by correcting the records for glacial isostatic adjustment and long-term subsidence. This project addresses three key hypotheses: global mean sea level during the Last Interglacial i) did not exceed 5 meters, a value significantly lower than current IPCC consensus; ii) might have oscillated within the interglacial, which might be indicative of northern and southern hemisphere ice melt that was out of phase; and iii) did not exceed maximum rates of 5 m per kyr, which is indicative of how fast or slow ice sheets might respond to future warming. The methodology that will be tested and developed within this research can be applied to other carbonate islands across the globe improving Last Interglacial sea level reconstructions at other locations, as well as during other time periods.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.