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

这项研究将产生高分辨率的重建海平面变化的过去2000年沿着纬度梯度的美国大西洋海岸从康涅狄格州到佛罗里达。需要对前卫星时代的海平面上升进行准确估计，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、海洋和冰盖之间质量交换所驱动的重力和旋转变化、温度和盐度变化引起的海洋密度（空间）变化以及其他因素，海平面变化在全球范围内并不均匀。 对盐沼沉积物中微体化石的分析将产生传递函数，以±0.1- 0.3米的垂直分辨率记录史前海平面。沉积物的年龄将通过补充测年方法确定。海平面重建将根据陆平面运动和海洋密度影响进行调整，以解决海平面变化的基本机制，重点是格陵兰和南极西部冰盖的对比影响之间的相互作用。格陵兰冰盖造成了沿沿着美国大西洋海岸从北到南的海平面上升幅度的显著纬度梯度，而南极西部冰盖的影响在空间上是均匀的。本研究将检验与海平面上升时间和幅度相关的四个具体研究假设：（1）20世纪世纪海平面上升的时间在不同地点之间是同步的，上升幅度从北向南增加;（2）与小冰期相关的海平面上升减速的幅度（3）中世纪气候异常期间海平面上升的幅度（公元1000-1500年）由南向北递增;海平面上升是气候变化的一个重要晴雨表，在21世纪可能对沿海地貌造成破坏性后果，人口和基础设施。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尚不清楚。该项目将进一步加深对海平面变化驱动机制的认识，提高预测21世纪海平面上升的能力。这种预测必须根据限制海平面空间和时间变化的观测结果进行验证。 该项目的结果将有助于评估国家在海平面上升和沿海应对方面的危害。

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.