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

科学家们继续权衡飓风对湿地的净影响。这些事件可能被认为是有益的，因为在浪涌淹没过程中发生的净沉积，或有害的，由于沼泽边缘的侵蚀和表面挖掘风暴波。这项研究将利用飓风厄玛留下的新的沉积学记录来研究南大西洋湾盐沼中的这些范例。站点范围从佛罗里达到南卡罗来纳州沿着纬度梯度增加春季潮差（1.7-2.4米），backbarrier沼泽宽度（5？7公里），流量加权平均悬浮泥沙浓度在附近的河流（13？27毫克/升）。它们表现出物理特性的变化，接近河流源，沉积物的可用性，这将有助于限制这些因素的相对作用，在风暴期间，沼泽地的沉积物。了解沼泽沉积作用对所有低洼植被海岸带的管理者都很有意义。量化沿海湿地如何应对相对海平面上升，以及风暴可能发挥的作用，对于模拟未来湿地演变和对风暴影响的长期恢复力至关重要。这项研究具有广泛的社会影响，因为盐沼提供的生态系统服务的重要性得到了公认，包括降低风暴潮高度和相关的社会经济成本，以及为鱼类种群提供苗圃。飓风厄玛在佛罗里达西海岸上空行进期间，其风力模式和规模在东南海岸沿线产生了强烈的沿着陆地风，并在南卡罗来纳州产生了大规模风暴潮。验潮仪数据表明，从佛罗里达州北方到南卡罗来纳州中部的沼泽地被洪水淹没至1 m深，并持续约7至17小时。相关的风暴潮沉积物可能很重要;其来源可能是当地的（沼泽或泻湖底部）或来自内陆架。该项目将调查伊尔玛风暴沉积物的性质（横向范围，厚度和来源）（与？背景？沉积）通过分析（1）浅沟（~20厘米）;（2）表面样品（已确定的Irma矿床）;（3）双短芯（每个50厘米长，直径8厘米）收集沿着两个横断面在每个网站从后障大陆（5？6个样芯/样带;总共约45个采样站）。我们还将绘制新的侵蚀特征，残骸线，植被破坏或埋葬，与伊尔玛有关。将对每个断面的两个岩心进行短寿命放射性同位素（210 Pb、137 Cs）采样，以提供数十年的吸积率，用于与事件沉积厚度进行比较。表面（Irma）沉积物和？背景？从两个加积岩芯深处采集的样品也将用于检查事件-沉积物物源特征，方法是分析大量生物地球化学特征（%TOC、C：N、Δ 13 CTOC、Δ 15 NTN）以及吸附到这些沉积物上/与这些沉积物共同沉积的硅藻和有机生物标志物组合，以确定风暴和非风暴期间的源差异（海洋、沼泽/泻湖、河流）。

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.