Collaborative Research: Hydrogeophysical monitoring and modeling of heterogeneity in salinization processes across the marsh-upland transition

气候变化导致的海平面上升可能会改变沿海地貌，对全球经济产生深远影响。在沿海地区，咸水淹没土壤的增加扰乱了养分和碳在土壤、大气和海洋之间的自然循环。沿海沼泽是陆地碳的重要汇，沿海沼泽的碳积累速度超过了温带森林。海平面的逐渐上升会导致咸水地下水缓慢的、横向的内陆移动，而风暴和大潮会导致咸水迅速淹没土壤，推动盐分垂直运移到土壤中。这些过程的生态后果是肉眼可见的，特别是在沿海沼泽和森林高地之间的过渡阶段，那里不断增加的土壤水盐分导致树木死亡和“幽灵森林”的形成。然而，土壤和地下水地下盐度变化的模式尚不清楚，特别是由于可能存在许多正反馈和负反馈机制。例如，如果枯死的树根和周围的土壤作为咸水运输的优先通道，个别树木的死亡可能会在局部加强盐分的垂直运输。沼泽-旱地过渡地区土壤质地(例如，颗粒大小)的变化也可能导致短期风暴事件期间和海平面逐渐上升时盐碱化速率的变化。该项目将应用电子地球物理成像技术和咸水运输的水文模型，以更好地理解地下非均质性(地质和植被诱导的)在调节多个沼泽-旱地过渡地区渐进和快速(风暴潮)水文过程中的作用。电子地球物理成像方法提供了关于盐度变化的空间连续、非侵入性信息。在这个项目中，这些方法将被用来监测盐度变化的演变，以应对重大风暴事件。这项工作将[1]产生数据和模拟，以改进风暴事件引起的盐碱化的概念模型，纳入地下非均质性的作用；[2]制定战略，通过纳入在空间和时间上丰富的地球物理观测，改进咸水运输的水文模型的预测能力；[3)在广泛的跨学科科学家群体中提高对地球物理成像技术的认识，以调查沿海地貌；[4]让不同的学生和早期职业科学家参加研究沼泽-隆起和过渡的讲习班。该项目由水文科学和既定的激励竞争研究计划(EPSCoR)共同资助。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。

Rising sea levels driven by climate change threaten to transform coastal landscapes with profound, global economic implications. Within the coastal zone, increased flooding of soils with saline water disrupts the natural cycling of nutrients and carbon between soils, the atmosphere and the ocean. Coastal marshes are an important sink of terrestrial carbon, and carbon accumulation rates in coastal marshes exceed those of temperate forests. Whereas gradual sea-level rise results in slow, lateral inland movement of saline groundwater, storms and large tides cause rapid inundation of soils with saltwater, driving vertical transport of salt into soils. The ecological consequences of these processes are visible to the naked eye, particularly across the transition between coastal marshes and forested uplands, where increasing soil water salinity results in tree mortality and the formation of ‘ghost forests’. However, the patterns of salinity change beneath the subsurface in soils and groundwater are unclear, particularly as numerous positive and negative feedback mechanisms may exist. For example, the death of individual trees may locally enhance vertical transport of salt if dead roots and surrounding soil serve as preferential pathways for the transport of saline water. Variations in soil texture (e.g., grain size) across the marsh-upland transition may also result in variability in rates of salinization both during short-term storm events and in response to gradual sea-level rise.This project will apply electrical geophysical imaging technologies and hydrological models of saltwater transport to improve understanding of the role of subsurface heterogeneity (both geology and vegetation induced) in regulating gradual and rapid (storm surge) hydrological processes across multiple marsh-upland transition zones. Electrical geophysical imaging methods provide spatially continuous, non-invasive information of variations in salinity. In this project, these methods will be deployed to monitor the evolution of salinity changes in response to major storm events. The work will [1] produce data and simulations to improve conceptual models for salinization resulting from storm events by incorporating the role of subsurface heterogeneity; [2] develop strategies to improve the predictive capabilities of hydrological models of saltwater transport by incorporating spatially and temporally rich geophysical observations; [3] promote awareness of geophysical imaging technologies for investigating coastal landscapes within a broad community of interdisciplinary scientists; [4] engage a diverse body of students and early career scientists in workshops studying the marsh-upland transition. This project is jointly funded by Hydrologic Sciences and the Established Program to Stimulate Competitive Research (EPSCoR).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.