Sustained upward groundwater discharge through salt marsh tidal creeks

Abstract

Salt marshes can export considerable nutrients and carbon to the ocean through submarine groundwater discharge (SGD). However, the complicated SGD processes in salt marshes remain poorly understood. Here, we first report the phenomenon of numerous highly saline artesian springs found in a salt marsh system of East China. Multiple methods including time‐series thermal monitoring, isotope signatures, and high‐resolution electrical resistivity tomography were combined to determine their origin and trajectory. Strong evidence suggests that these springs keep discharging even during high tide and represent a long‐term re‐distribution process of the ancient marine water trapped in the unconfined aquifer. This new pattern of spring‐derived groundwater flow indicates a hidden SGD pathway and has significant implications for studies concerning SGD‐derived fluxes in similar multi‐aquifer‐aquitard coastal systems.

The two salinity peaks mode of marine salt supply to coastal underground brine during a single tidal cycle

“…With the upgrading of hydrogeophysical monitoring instruments and the optimization of geophysical data interpretation methods, the Electrical resistivity tomography (ERT) is widely used to monitor and research groundwater hydrological processes in in-situ coastal zones. ERT survey results from different times can provide information about brackish water and seawater intrusion processes that can be analyzed and used to establish different types of coastal seawater-groundwater exchange models (Franco et al, 2009;Misonou et al, 2013;Fu et al, 2020;Zhang, 2021;Zhan et al, 2023;Zhang et al, 2023). Further, the Archie formula, Manning formula, and the salinity box model can be combined to support quantification of the groundwater discharge and salt flux in the tidal flat area Zhang Y. et al, 2021Zhang Y. et al, , 2023Xing et al, 2023).…”