RAPID: Collaborative Research: Storm Surge Deposition on Salt Marshes: Impacts of Hurricane Irma from Florida to South Carolina

RAPID：合作研究：盐沼上的风暴潮沉积：飓风艾尔玛从佛罗里达州到南卡罗来纳州的影响

• 批准号: 1800825
• 负责人: Christopher Hein
• 金额: $ 0.45万
• 依托单位: College of William & Mary Virginia Institute of Marine Science
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-11-15 至 2018-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1800825&HistoricalAwards=false
• 关键词: RAPID; Collaborative; Research; Storm; Surge

Scientists continue to weigh the net impact of hurricanes on wetlands. These events may be considered beneficial because of net sedimentation that occurs during surge inundation, or detrimental due to erosion of the marsh edge and surface excavation by storm waves. This study will exploit the new sedimentologic record left by Hurricane Irma to examine these paradigms in the salt marshes of the South Atlantic Bight. Sites range from Florida to South Carolina along a latitudinal gradient of increasing spring tidal range (1.7-2.4 m), backbarrier marsh width (5?7 km), and flow-weighted average suspended sediment concentrations in nearby rivers (13?27 mg/l). They exhibit variations in physical characteristics, proximity to fluvial source, and sediment availability that will help constrain the relative role of these factors in contributing sediment to marshes during storms. Understanding marsh sedimentation is of interest to all stewards of low-lying vegetated coastal zones. Quantifying how coastal wetlands accrete in response to relative sea-level rise, and the contributions that storms may play, is paramount to modeling future wetland evolution and long-term resilience to storm impacts. This study has broad societal implications given the recognized importance of the ecosystem services provided by salt marshes, including reducing storm surge height and related socioeconomic costs, and providing nurseries for fish stocks. While Hurricane Irma tracked over the west coast of Florida, the wind patterns and size of the storm created strong onshore winds along the southeast coast, producing a large stormsurge up into South Carolina. Tide gauge data indicate that marshes from northern FL to central SC were flooded to a depth of 1 m, and remained so for ~7 to 17 hrs. Associated storm surge deposits are likely to be significant; their source may be local (marshes or lagoon floor) or from the inner shelf. The project will investigate the nature (lateral extent, thickness, and provenance) of Irma storm deposits (compared to ?background? sedimentation) through the analysis of (1) shallow trenches (~20 cm); (2) surface samples (of identified Irma deposits); and (3) double short cores (each 50-cm long, 8 cm in diameter) collected along two transects at each site from the backbarrier to mainland (5?6 cores/transect; ~45 sampling stations total). We will also map new erosional features, wrack lines, and vegetation damage or burial, related to Irma. Two cores from each transect containing a clear, representative Irma deposit will be sampled for short-lived radioisotope (210Pb, 137Cs) to provide multi-decadal accretion rates for comparison with event-sedimentation thicknesses. Surface (Irma) deposits and ?background? samples from depth in the two accretion cores, will also be used to examine event-sediment provenance signatures through analysis of bulk biogeochemical characteristics (%TOC, C:N, ä13CTOC, ä15NTN), and assemblages of diatoms and organic biomarkers adsorbed to/co-deposited with these sediments to determine source differences (marine, marsh/lagoon, fluvial) between storm and non-storm periods.

科学家们继续权衡飓风对湿地的净影响，因为洪水泛滥期间发生的净沉积，或由于风暴波侵蚀沼泽边缘和地表开挖而造成的困扰，这些事件可能被认为是有益的。飓风艾尔玛留下的沉积学记录，用于检查南大西洋湾盐沼中的这些范例。地点范围从佛罗里达州到南卡罗来纳州，沿着春潮范围不断增加的纬度梯度（1.7-2.4）。米）、后障沼泽宽度（5-7 公里）和附近河流的流量加权平均悬浮沉积物浓度（13-27 毫克/升）。有助于限制这些因素在风暴期间向沼泽沉积的相对作用，了解沼泽沉积对于低洼植被沿海地区的所有管理者来说都是有意义的，量化沿海湿地如何随着相对海平面上升而增长。鉴于盐沼提供的生态系统服务（包括降低风暴潮高度和相关）的重要性已得到公认，这项研究具有广泛的社会影响。当飓风“艾尔玛”席卷佛罗里达州西海岸时，风暴的风型和规模在东南海岸产生了强烈的陆上风，并在南卡罗来纳州产生了巨大的风暴潮。表明来自佛罗里达州北部的沼泽至 SC 中部被淹没至 1 m 深度，并持续约 7 至 17 小时。相关风暴潮沉积物可能来自当地（沼泽或泻湖底部）或来自内陆架。项目将通过分析 (1) 浅沟（约 20 厘米）（2）表面样本来调查艾尔玛风暴沉积物的性质（横向范围、厚度和来源）（与“背景”沉积物相比）； （已识别的 Irma 沉积物）；（3）沿每个地点从后屏障到大陆的两条样线收集的双短岩心（每个样线长 50 厘米，直径 8 厘米）（每样线 5?6 个岩心；约 45 个采样站）我们还将绘制与 Irma 相关的新侵蚀特征、残骸线和植被破坏或埋藏图，并对每个样带中含有清晰、有代表性的 Irma 矿床的两个岩心进行采样，以获取短寿命放射性同位素。 （210Pb，137Cs）提供了与事件沉积厚度进行比较的数十年沉积率和两个沉积核心深度的“背景”样本，也将用于通过以下方式检查事件沉积物来源特征。批量生物地球化学特征（%TOC、C:N、ä13CTOC、ä15NTN）和组合分析硅藻和有机生物标记物吸附在这些沉积物上/与这些沉积物共同沉积，以确定风暴期和非风暴期之间的来源差异（海洋、沼泽/泻湖、河流）。