Collaborative Research: Middle to Late Holocene Sea-Level Change and Coastal Evolution, Northern Gulf of Mexico Coast

地球上的一些海岸线都有完整的全新世海平面变化记录，但在其他地方却存在争议。 一个有争议的地区是美国墨西哥湾沿岸，那里的两个对比模型在文献中持续了几十年，并得到了最近NSF赞助的研究的新支持。 一种模式认为海平面在过去的6,000至7,000年中不断上升，而另一种模式认为海平面在6,000至7,000年前达到现在的海拔高度，并从那时起在现在海拔高度的1至2米范围内波动。 过去对墨西哥湾沿岸沿着的研究是在不同的地区进行的，由不同的调查人员使用不同的方法进行的。 这些相互冲突的模型尚未得到协调，仍然不确定不同的结果是否反映了海平面变化的固有空间变异性，所使用的各种方法的分辨率差异，或两者的某种组合。 这项合作研究汇集了研究人员，他们产生了相互矛盾的结果，但现在将把各自的方法应用到相同的领域。 研究人员将重点关注路易斯安那州西南部、亚拉巴马州和佛罗里达州西北部的非沉降、非三角洲地区。 该项目的主要目标是：（1）通过研究非三角洲沼泽沉积物中的基泥炭记录全新世（地面）水位变化;（B）确定现代贝壳堤和海滩山脊沉积物中的精确海平面指标;（c）在贝壳堤和海滩山脊地层记录中跟踪海平面指标随时间的变化。 预计这一方法将根据基泥炭数据和贝壳堤和海滩山脊沉积物为每个研究区制作高分辨率的相对海平面曲线，以便调和这两种方法，并提供一个内部一致的海平面变化及其空间变异性的图像。 每条曲线将被校准到精确的GPS高程，并将锚定放射性碳和/或光激发光dating.Development的相对海平面变化和它的空间变异性沿着美国墨西哥湾沿岸的一个更精确和综合的理解将有一些学科和区域的影响。 现有的海平面变化模型对全球气候和冰量重建以及对区域沿海景观演变、人类对过去海平面变化的适应以及沿海系统对未来气候和海平面变化的反应方式的研究具有显著不同的影响。 海平面变化也是墨西哥湾沿岸沿着人与环境相互作用中最紧迫的问题之一，特别是沿着密西西比三角洲，那里将有数十亿美元投资于海岸恢复。 目前，这些努力缺乏海平面变化的自然背景速率、其区域尺度空间变异性及其近期轨迹的基本基线。 这项研究将提供这样一个基线，并将与沿海恢复工作相结合。

A number of Earth's coastlines have well-constrained records of Holocene sea-level change, yet controversy prevails elsewhere. One controversial area is the U.S. Gulf of Mexico coast, where two contrasting models have persisted in the literature for decades and have seen renewed support from recent NSF-sponsored research. One model views sea level as continually rising through the last 6,000 to 7,000 years, whereas the other holds that sea level reached present elevations 6,000 to 7,000 years ago and has oscillated within 1 to 2 meters of present elevations since that time. Past research along the Gulf Coast has been undertaken in different areas and by different investigators using different methods. These conflicting models have not been reconciled, and it remains uncertain whether disparate results reflect inherent spatial variability in sea-level change, differences in resolution of the various methods used, or some combination of the two. This collaborative research brings together investigators that have produced conflicting results but who now will apply their respective approaches to the same field areas. The researchers will focus on non-subsiding, non-deltaic sites in southwestern Louisiana, Alabama, and northwestern Florida. Major goals of the project are (1) the documentation of Holocene (ground) water-level change from studies of basal peats in non-deltaic marsh sediments; (b) definition of precise sea-level indicators in modern chenier and beach-ridge deposits; and (c) tracking of changes in the elevation of sea-level indicators through time within chenier and beach ridge stratigraphic records. This approach is expected to produce high-resolution relative sea-level curves for each study area from basal-peat data and from chenier and beach-ridge deposits so as to reconcile the two approaches and provide an internally consistent picture of sea-level change and its spatial variability. Each curve will be calibrated to precise GPS elevations and will be anchored by radiocarbon and/or optically stimulated luminescence dating.Development of a more precise and integrated understanding of relative sea-level change and its spatial variability along the U.S. Gulf of Mexico coast will have a number of disciplinary and regional implications. Existing models for sea-level change have significantly different implications for global climate and ice volume reconstructions as well as for studies of regional coastal landscape evolution, of human adaptations to past sea-level change, and of the ways that coastal systems might respond to future climate and sea-level change. Sea-level change is also one of the most pressing problems in human-environment interactions along the Gulf of Mexico coast, especially along the Mississippi delta, where billions of dollars will be invested in coastal restoration. At present, these efforts lack a fundamental baseline for natural background rates of sea-level change, its regional-scale spatial variability, and its recent trajectory. This research will provide such a baseline, and will be integrated with coastal restoration efforts.