Assessing the Driving Forces of Submarine Groundwater Discharge

海底地下水排放（SGD）是营养物质和其他溶解成分从陆地到沿海海洋的重要途径，但在很大程度上尚未量化。沿海海洋学家和水文学家已经证明，只要有正水头的含水层与地表水体通过水力连接，新鲜地下水就会缓慢而持续地通过沉积物渗漏。现在人们认识到，相当数量的海水也通过沿海含水层系统再循环，淡水和咸水的输入都向沿海水域提供营养物质和其他溶解的固体。然而，驱动过程的相对重要性以及咸水流量与淡水排放耦合的程度仍然没有得到很好的理解，并且缺乏预测能力。出于这个原因，佛罗里达州立大学的研究人员将调查驱动淡水和含盐地下水排放的力量。由于陆地（水力梯度，季节性补给循环）和海洋（波浪设置，潮汐泵送，水位差异）的力量驱动地下流体流经沿海含水层和近岸沉积物，该科学家团队将通过跨学科的方法来研究这些过程。从两端（陆地和海洋）以及两个学科（水文学和海洋学）解决SGD问题至关重要，因为驱动力在时间和空间上是重叠的，通过沿海沉积物测量到的流体流动往往是复合强迫的结果。该项目将通过长期测量（即同位素示踪剂、渗透仪）、水文/地球物理调查和数值模拟的组合来分离和评估这些强迫功能。目标是开发与SGD及其驱动力相关的所有参数的长期数据集。由于许多SGD驱动器具有已知的时间变化，因此将测量参数的频率和随后的SGD响应，以解卷积力的影响。就更广泛的影响而言，这项研究将显著推进我们对SGD控制机制的理解。建议在沿岸发展前进行工程，可提供基线，以评估未来商业/住宅发展对沿岸含水层的影响。为向沿岸区管理人员发放有关新港发展及其影响的资料，我们会在计划的第三年举办工作坊。研究生和本科生将参与该项目的实地和实验室研究。

ABSTRACTOCE-0520723Submarine groundwater discharge (SGD) represents an important, yet largely unquantified pathway for nutrients and other dissolved constituents from land to the coastal ocean. Coastal oceanographers and hydrologists have shown that slow yet persistent seepage of fresh groundwater through sediments occurs wherever an aquifer with a positive head is hydraulically connected to a surface water body. It is now recognized that a considerable amount of seawater is also recirculated through coastal aquifer systems and that both fresh and saline water inputs contribute nutrients and other dissolved solids to coastal waters. However, the relative importance of the driving processes and the extent to which saline water flow is coupled to fresh water discharges is still not well understood and the predictive capabilities are lacking. For this reason, researchers at Florida State University will investigate the forces that drive both fresh and saline groundwater discharges. Since both terrestrial (hydraulic gradient, seasonal recharge cycle) and marine (wave setup, tidal pumping, water level differences) forces drive subsurface fluid flows through coastal aquifers and nearshore sediments, this team of scientists will examine these processes via a cross-disciplinary approach. It is critical to tackle the problem of SGD from both ends (terrestrial and marine), and from both disciplines (hydrology and oceanography) because driving forces overlap in time and space and the resultant fluid flow measured through coastal sediments is often a result of composite forcing. The project will separate and evaluate these forcing functions by a combination of long-term measurements (i.e., isotopic tracers, seepage meters), hydrological/geophysical investigations, and numerical modeling. The goal is to develop a long-term data set on all parameters that are relevant to SGD and its driving forces. Since many SGD drivers have known temporal variations, the frequency of the parameters and the ensuing SGD responses will be measured to deconvolute the influence of the forces.In terms of broader impacts, this study will significantly advance our understanding of the mechanisms controlling SGD. Proposing to carry out the work prior to coastal development at the site will provide a baseline from which to assess the impact of commercial/residential development on coastal aquifers in the future. To disseminate information to coastal zone manager on SGD and its implications, a workshop will be held during the third year of the project. Graduate and undergraduate students will be involved in the field and laboratory studies of the project.