Collaborative Research: Millennial-Scale Records of Sea-level Change Along the Atlantic Coast of the United States

这项研究将对美国大西洋海岸从康涅狄格州到佛罗里达州的纬度梯度上过去2000年的海平面变化进行高分辨率重建。需要准确估计前卫星时代的海平面上升，以便为21世纪的预测提供适当的背景，并验证地球物理和气候模型。记录海平面的地理趋势很重要，因为由于固体地球的均衡(陆地水平)运动、海洋和冰盖之间的质量交换引起的重力和自转变化、温度和盐度变化引起的海洋密度(立体)变化以及其他因素，海平面的变化在全球范围内并不是一致的。对盐沼沉积物中的微体化石的分析将产生记录史前海平面垂直分辨率为±0.1-0.3m的传递函数。沉积物的年龄将通过补充的测年方法确定。海平面重建将根据陆地水平运动和海洋密度的影响进行调整，以解决海平面变化的根本机制，重点是格陵兰冰盖和南极西部冰盖的对比影响之间的相互作用。格陵兰冰盖在美国大西洋沿岸从北到南的海平面上升幅度上产生了显著的纬度梯度，而南极西部冰盖的影响在空间上是一致的。与海平面上升的时间和幅度有关的四个具体研究假设将被检验：(1)20世纪海平面上升的时间在不同地点之间是同步的，这种上升的幅度从北到南递增；(2)与小冰期(公元1500-1850年)相关的海平面上升的减速幅度从南到北递增；(3)中世纪气候异常(公元1000-1500年)的海平面上升幅度从南到北递增；海平面上升的速度从公元0到1000年是恒定的。海平面上升是气候变化的重要晴雨表，对21世纪的沿海地貌、人口和基础设施具有潜在的破坏性后果。对过去2000年海平面变化的了解有限，对中世纪气候异常、小冰期和20世纪变暖等已知气候偏差的反应也是未知的。该项目将增加对海平面变化驱动机制的认识，提高对21世纪海平面上升的预测能力。这种预测必须与限制海平面空间和时间变异性的观测相对照。该项目的成果将有助于评估与海平面上升和沿海应对措施有关的国家危害。

This research will produce high-resolution reconstructions of sea-level change for the last 2000 years along the latitudinal gradient of the Atlantic Coast of the United States from Connecticut to Florida. Accurate estimates of sea-level rise in the pre-satellite era are needed to provide an appropriate context for 21st century projections and to validate geophysical and climate models. Documenting geographic trends in sea level is important because sea-level changes are not globally uniform owing to isostatic (land-level) movements of the solid Earth, gravitational and rotational changes driven by the exchange of mass between oceans and ice sheets, ocean density (steric) changes from temperature and salinity variations, and other factors. Analysis of microfossils from salt marsh sediments will generate transfer functions that document prehistoric sea level at a vertical resolution of ±0.1-0.3m. The age of the sediments will be determined from complementary dating methods. Sea-level reconstructions will be adjusted for land-level movements and ocean density influences to address the underlying mechanisms of sea-level change, focusing on the interplay between the contrasting influences of both the Greenland and Western Antarctic Ice Sheets. Whereas the Greenland Ice Sheet produces a significant latitudinal gradient in the magnitude of sea-level rise from north to south along the Atlantic Coast of the United States, the influence of Western Antarctic Ice Sheet is spatially uniform. Four specific research hypotheses related to the timing and magnitude of sea-level rise will be tested: (1) The timing of 20th century sea-level rise was synchronous between sites and the magnitude of this rise increased from north to south; (2) The magnitude of a deceleration in sea-level rise associated with the Little Ice Age (AD 1500-1850) increased from south to north; (3) The magnitude of sea-level rise during the Medieval Climate Anomaly (AD 1000-1500) increased from south to north; and (4) The rate of sea-level rise was constant from AD 0 to 1000.Sea-level rise is a vital barometer of climate change, with potentially devastating consequences in the 21st century for coastal landforms, populations and infrastructure. Knowledge of sea-level variability during the past 2000 years is limited and the response to known climate deviations such as the Medieval Climate Anomaly, Little Ice Age and 20th century warming is unknown. This project will increase comprhension of the driving mechanisms of sea-level change and enhance the ability to predict 21st century sea-level rise. Such predictions must be validated against observations that constrain spatial and temporal variability in sea-level. The results of this project will contribute to the assessment of national hazards with respect to sea-level rise and coastal responses.