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CAREER: Dynamic sea-level trends during the past two millennia

职业：过去两千年海平面的动态趋势

基本信息

批准号：
1942563
负责人：
Andrew Kemp
金额：
$ 77.08万
依托单位：
Tufts University
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-04-01 至 2025-03-31
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1942563&HistoricalAwards=false
关键词：
CAREER Dynamic sea level trends

项目摘要

Relative sea level (RSL; the height of the sea-surface with respect to the land) changes across space and through time in response to a wide range of physical processes that operate on timescales from minutes to millennia and on local to global spatial scales. Projections of future climate indicate that changes to the strength and/or position of ocean currents and prevailing winds will cause RSL rise along much of the U.S. Atlantic coast to exceed the global mean by pushing existing ocean water toward the coast (termed dynamic sea-level change). The relationship between coastal RSL and ocean/atmospheric circulation can be observed on timescales of months to a few years in instrumental datasets, but it remains unclear if such changes can be sustained on longer timescales. This project will reconstruct RSL changes during the past ~2000 years from Prince Edward Island to South Carolina using coastal sediment to explore if and why dynamic sea-level changes occurred over multiple decades and centuries. These reconstructions will support coastal management by helping to inform and constrain projections of 21st century regional-scale RSL rise. Public scientific literacy will be promoted through an original art exhibition (in collaboration with the School of the Museum of Fine Arts) that explores the causes and ramifications of regional sea-level rise.Instrumental datasets (e.g., tide-gauge measurements) and model projections demonstrate that dynamic sea-level changes along the Atlantic coast of North America have a spatial expression that is characteristic of the underlying physical cause(s). Since these datasets are short and fragmentary, proxy RSL reconstructions are needed to quantify dynamic sea-level change on multi-decadal to centennial timescales. This project will produce high resolution and near-continuous RSL reconstructions spanning the past ~2000 years from two sites in each of Prince Edward Island, Maine, and South Carolina using foraminifera preserved in dated sequences of salt-marsh sediment. These locations were chosen because of their sensitivity to dynamic sea-level change in model simulations and to complement the distribution of existing RSL reconstructions. The vertical distribution of salt marshes (and foraminifera that live on them) is fundamentally linked to tide levels and therefore sea level. Under conditions of RSL rise salt marshes accumulate sediment to maintain their position in the tidal frame. The resulting sedimentary sequences contain the identifiable remains of plants and foraminifera that lived on paleo salt marsh surfaces and are a detailed archive of RSL change. Along much of the Atlantic coast of North America ongoing glacio-isostatic adjustment drives long-term RSL rise and the creation of accommodation space (approximately 1–3 m for the study areas in the past ~2000 years) that is filled by salt-marsh sediment. Dynamic sea-level changes overprint this underlying RSL trend and can be identified in sufficiently detailed RSL reconstructions. An age-depth model will be created for each of the six cores using radiocarbon dating of plant remains and recognition of pollution trends and events of known age in downcore profiles of elemental and isotopic abundance. The height of former RSL will be reconstructed using transfer functions trained on the observable relationship between assemblages of foraminifera and tidal elevation on salt marshes in the three study areas. The resulting RSL reconstructions will have the temporal and vertical resolution necessary to reliably identify relatively small and short-lived dynamic sea-level variability. Analysis of these new records alongside existing reconstructions using a spatio temporal model will identify regional patterns of coherent sea level variability in the North Atlantic Ocean from which the role of ocean and/or atmospheric dynamics as a driver of sea-level trends will be quantified. This long-term perspective on ocean/atmosphere conditions, climate forcing, and sea-level rise will generate insight into the causes and magnitude of past, present, and future changes in the coupled climate-sea level system.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.

相对海平面(RSL；海面相对于陆地的高度)在空间和时间上随着各种物理过程的变化而变化，这些物理过程在几分钟到几千年的时间尺度上以及在地方到全球的空间尺度上运作。对未来气候的预测表明，洋流和盛行风的强度和/或位置的变化将通过将现有海水推向海岸，导致美国大西洋沿岸大部分地区的RSL上升超过全球平均水平(称为动态海平面变化)。在仪器数据集中，可以在几个月到几年的时间尺度上观察到沿海RSL与海洋/大气环流之间的关系，但尚不清楚这种变化能否在更长的时间尺度上持续下去。该项目将利用海岸沉积物重建过去2000年从爱德华王子岛到南卡罗来纳州的RSL变化，以探索海平面是否以及为什么会发生数十年和数百年的动态变化。这些重建将通过帮助告知和限制21世纪区域范围内RSL上升的预测来支持沿海管理。将通过一个原创艺术展(与美术博物馆学院合作)促进公众的科学素养，该艺术展探索区域海平面上升的原因和后果。仪器数据集(例如，验潮仪测量)和模型预测表明，北美大西洋沿岸海平面的动态变化具有潜在物理原因特有的空间表达(S)。由于这些数据集很短且不完整，需要代理RSL重建来量化几十年到百年时间尺度上的动态海平面变化。该项目将利用保存在盐沼沉积物年代序列中的有孔虫，从爱德华王子岛、缅因州和南卡罗来纳州各两个地点制作跨越过去约2000年的高分辨率和几乎连续的RSL重建。之所以选择这些位置，是因为它们对模型模拟中的海平面动态变化很敏感，并补充了现有RSL重建的分布。盐沼(以及生活在盐沼上的有孔虫)的垂直分布基本上与潮汐水平有关，因此也与海平面有关。在RSL上升的条件下，盐沼堆积沉积物以保持其在潮汐框架中的位置。由此产生的沉积序列包含了生活在古盐沼表面的可识别的植物和有孔虫遗骸，是RSL变化的详细档案。在北美大西洋沿岸的大部分地区，持续的冰川均衡调整推动了RSL的长期上升，并创造了由盐沼沉积物填充的可容纳空间(过去2000年，研究区约为1-3m)。海平面的动态变化覆盖了这一潜在的RSL趋势，并可以在足够详细的RSL重建中识别出来。将利用植物遗骸的放射性碳测年以及在元素和同位素丰度的岩心下部剖面中识别污染趋势和已知年龄事件，为六个岩芯中的每一个岩心建立年龄深度模型。利用三个研究区盐沼有孔虫组合与潮汐高程之间的可观测关系训练传递函数，重建原RSL的高度。由此得到的RSL重建将具有可靠地识别相对较小和短暂的动态海平面变化所需的时间和垂直分辨率。利用时空模型对这些新记录和现有重建数据进行分析，将查明北大西洋海平面变化连贯的区域模式，由此将量化海洋和(或)大气动力作为海平面趋势驱动因素的作用。这种对海洋/大气条件、气候强迫和海平面上升的长期视角将使我们深入了解气候-海平面耦合系统过去、现在和未来变化的原因和规模。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。