Aquifer systems extending far offshore on the U.S. Atlantic margin

Area of Science:

• Geophysics
• Hydrogeology
• Marine Geology

Background:

• Low-salinity submarine groundwater on continental shelves is globally present but poorly quantified.
• Emplacement mechanisms include glacial processes and connections to onshore hydrologic systems.
• Limited observations hinder understanding of offshore groundwater distribution and volume.

Purpose of the Study:

• To image and constrain the extent of offshore aquifers using geophysical methods.
• To investigate the connection between onshore and offshore hydrologic systems.
• To identify structural controls on submarine groundwater distribution.

Main Methods:

• Shallow water electromagnetic geophysical surveys were employed.
• Data were collected offshore New Jersey and Martha's Vineyard.
• Aquifer continuity and extent were mapped.

Main Results:

• Laterally continuous aquifers were imaged extending 90 km offshore.
• A connection between modern onshore and offshore hydrologic systems was identified.
• Clinoforms were identified as a novel structural control on groundwater extent and upwelling.
• A 350 km long submarine aquifer system containing approximately 2800 km³ of low-salinity groundwater was delineated.

Conclusions:

• The U.S. Atlantic margin hosts a significant, extensive submarine groundwater system.
• Clinoforms play a crucial role in controlling offshore groundwater.
• Findings improve models of continental shelf processes and provide insights into shelf biogeochemistry.