Collaborative research: Arctic Shelf sediment fate - an observational and modeling study of sediment pathways and morphodynamic feedbacks in a changing polar environment

合作研究：北极陆架沉积物命运——极地环境变化中沉积物路径和形态动力学反馈的观测和建模研究

• 批准号: 1913195
• 负责人: Emily Eidam
• 金额: $ 49.26万
• 依托单位: University of North Carolina at Chapel Hill
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2023-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1913195&HistoricalAwards=false
• 关键词: Collaborative; research; Arctic; Shelf; sediment

In many coastal environments, shoreline erosion provides a major source of sediment to the ocean. Over time, this material is transported along the shore (to nourish beaches) and/or offshore (to form deeper-water mud patches). Some of the highest rates of coastal erosion occur in the Arctic because ground containing permafrost thaws easily under the influence of warm ocean water and wave attack. But once that sediment enters the Arctic Ocean, we know very little about where it goes. Studies of sediment transport have been a critical part of coastal management and geologic inquiry for the past several decades but have focused on temperate and tropical environments not impacted by seasonal sea ice. We have a critical need to expand these studies to the Arctic in order to improve our understanding of the fate of sediments, which can re-shape coastlines, change the character of the seabed, and transfer nutrients from land to ocean. This research is timely in light of accelerating coastal erosion associated with reductions in seasonal sea-ice extent and intensifying wave energy, trends which are forecast to continue. This study is designed to determine the primary pathways of sediments in the coastal ocean during the open-water season, when frequent wind storms are expected to mobilize sediments recently delivered to the seabed. Measurements will include particle concentrations, sediment migration on time scales of seconds to months, seabed composition, and seabed geotechnical properties. These data will be used to model how the Alaskan continental shelf may evolve over thousand-year timescales in response to changing shorelines and wave conditions. This project will be tackled by a team of researchers with field, geotechnical, and modeling expertise. Networking with local communities, training of graduate students, and engagement with undergraduates at the University of North Carolina through classes as well as programs aimed at introducing students from underrepresented groups to scientific research are planned.Accelerating coastal erosion is one of the critical environmental changes occurring in the Arctic and is associated with intensifying wave climates driven by annual reductions in sea-ice extent. At present, parts of the Alaskan Arctic coastline are experiencing some of the greatest rates of coastal erosion worldwide. These rates are accelerating, representing an increased source term of sediment and associated nutrients into the coastal ocean. While studies of continental shelf dynamics have provided great insights to sediment transport at temperate and tropical latitudes, we know relatively little about the pathways of sediment on Arctic continental shelves. These remote environments are shrouded by ice for up to nine months of the year and experience unique processes like ice pressure-ridge formation, disturbance of the seabed by anchor-ice growth, and 'strudel scour' during breakup. These processes can confound traditional seabed signatures of sediment accumulation. Thus, this project proposes to pair measurements of seabed properties with dynamic measurements of sediment fluxes within the water column during the storm season to determine the key mechanisms and pathways of sediment flux. Field data will be used to drive morphostatic and morphodynamic models of shelf profile evolution to determine feedbacks between wave propagation, erosion, and changes in the shelf profile over millennial timescales. The field site encompasses Harrison Bay and the adjacent shelf, which receives sediment from rapidly retreating bluffs and the Colville River.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.

在许多沿海环境中，海岸线侵蚀是海洋沉积物的主要来源。随着时间的推移，这些物质被沿着海岸（滋养海滩）和/或离岸（形成深水泥斑）运输。一些最高速率的海岸侵蚀发生在北极，因为含有永久冻土的地面在温暖的海水和波浪袭击的影响下很容易融化。但是一旦沉积物进入北冰洋，我们对它的去向知之甚少。在过去几十年中，沉积物输运研究一直是海岸管理和地质调查的一个关键部分，但重点是不受季节性海冰影响的温带和热带环境。我们迫切需要将这些研究扩大到北极，以提高我们对沉积物命运的理解，沉积物可以重塑海岸线，改变海底的特征，并将营养物质从陆地转移到海洋。鉴于季节性海冰范围减少和波浪能增强导致海岸侵蚀加速，预计这一趋势将继续下去，这项研究是及时的。这项研究的目的是确定在开放水域的季节，当频繁的风暴预计将动员最近交付到海底的沉积物在沿海海洋沉积物的主要途径。测量将包括颗粒浓度、沉积物迁移（秒至月的时间尺度）、海底成分和海底岩土特性。这些数据将用于模拟阿拉斯加大陆架在千年时间尺度内如何应对不断变化的海岸线和波浪条件。该项目将由一个具有现场，岩土工程和建模专业知识的研究人员团队解决。计划与当地社区建立联系，培训研究生，并通过课程和项目与北卡罗来纳州大学的本科生进行接触，这些课程和项目旨在向来自代表性不足群体的学生介绍科学研究。海岸侵蚀加速是北极发生的关键环境变化之一，与海冰范围每年减少导致的波浪气候加剧有关。目前，阿拉斯加北极海岸线的部分地区正经历着世界上最严重的海岸侵蚀。这些速率正在加快，代表着沉积物和相关营养物进入沿海海洋的源项增加。虽然对大陆架动态的研究为温带和热带地区的沉积物迁移提供了重要的见解，但我们对北极大陆架上沉积物的路径知之甚少。这些偏远的环境一年中有九个月被冰覆盖，并经历了独特的过程，如冰压脊的形成，锚冰生长对海床的扰动，以及解体期间的“果馅卷冲刷”。这些过程可能混淆传统的海底沉积物积聚特征。因此，本项目建议将海底特性测量与风暴季节水柱内沉积物通量的动态测量结合起来，以确定沉积物通量的关键机制和路径。现场数据将被用来驱动大陆架剖面演变的形态静态和形态动力学模型，以确定千年时间尺度上的波传播、侵蚀和大陆架剖面变化之间的反馈。现场包括哈里森湾和邻近的大陆架，它接收沉积物从迅速撤退的悬崖和科尔维尔河。这个奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。

项目成果

Increasing Wave Energy Moves Arctic Continental Shelves Toward a New Future

波浪能的增加使北极大陆架走向新的未来

• DOI: 10.1029/2021jc018374
• 发表时间: 2022
• 期刊: Journal of Geophysical Research: Oceans
• 作者: Malito, John;Eidam, Emily;Nienhuis, Jaap
• 通讯作者: Nienhuis, Jaap

Seabed grain-size data from Harrison Bay (Beaufort Sea continental shelf), Alaska 2021

阿拉斯加哈里森湾（波弗特海大陆架）海底粒度数据 2021

• DOI: 10.18739/a2jw86p50
• 发表时间: 2023
• 期刊: NSF Arctic Data Center
• 作者: Eidam, Emily

Blossom Shoals water-column, seabed sediment, and bathymetry data. Icy Cape, Chukchi Sea, Alaska. 2019-2020.

Blossom Shoals 水柱、海底沉积物和测深数据。

• DOI: 10.18739/a2862bd1g
• 发表时间: 2023
• 期刊: NSF Arctic Data Center
• 作者: Eidam, Emily;Thomson, Jim;Malito, John;Hosekova, Lucia
• 通讯作者: Hosekova, Lucia