Submarine Groundwater Discharge: Updates on Its Measurement Techniques, Geophysical Drivers, Magnitudes, and Effects

Makoto Taniguchi,Isaac R Santos,Kimberly M Burnett,Ryo Sugimoto,Guebuem Kim,Henrietta Dulai,Nils Moosdorf,Thomas Stieglitz,William C Burnett

doi:10.3389/fenvs.2019.00141

Abstract

The number of studies concerning Submarine Groundwater Discharge (SGD) grew quickly as we entered the 21st century. Many hydrological and oceanographic processes that drive and influence SGD were identified and characterized during this period. These processes included tidal effects on SGD, water and solute fluxes, biogeochemical transformations through the subterranean estuary, and material transport via SGD from land to sea. Here we compile and summarize the significant progress in SGD assessment methodologies, considering both the terrestrial and marine driving forces, and local as well as global evaluations of groundwater discharge with an emphasis on investigations published over the past decade. Our treatment presents the state-of-the-art progress of SGD studies from geophysical, geochemical, bio-ecological, economic, and cultural perspectives. We identify and summarize remaining research questions, make recommendations for future research directions, and discuss potential future challenges, including impacts of climate change on SGD and improved estimates of the global magnitude of SGD.

Highlights

Some material pathways from land to the sea are obvious while others are not so apparent
We have updated the state of current research concerning Submarine Groundwater Discharge (SGD) focusing on findings over the last decade, the “mature stage” of SGD research
Our treatment centered on the updates of measurement techniques, geophysical drivers, magnitudes, and effects

Summary

INTRODUCTION

Some material pathways from land to the sea are obvious while others are not so apparent. Separating the relative contribution of the different physical processes driving saline SGD is important because longer residence times of seawater within sediments will have a greater impact on the geochemical composition of the exchanging seawater (Seidel et al, 2014; Tamborski et al, 2017a). The SGD input of dissolved nutrients was shown to be at least 5 times higher than river input

Geophysical Methodology

Geochemical Methodology

Findings

SUMMARY AND REMAINING QUESTIONS