International
Aaron Micallef / Eos

World - Freshened Groundwater in the Sub-Seafloor

Scientists are using a variety of geochemical, geophysical, and numerical methods to study offshore freshened groundwater and better understand its role in the global water cycle.

Offshore freshened groundwater (OFG) is water hosted in sediments and rocks below the seafloor. It can be found offshore of most continents around the world and could possibly become a source of potable water for human populations living near the coast. A recent article in Reviews of Geophysics describes a range of geochemical, geophysical, and modeling approaches that have been used to investigate OFG systems. Here, the lead author gives an overview of what we know about OFG and where it occurs, and what research questions remain.

What is offshore freshened groundwater?

Offshore freshened groundwater (OFG) is water that has a salinity lower than seawater and that is stored in sediments and rocks below the seafloor. Freshened groundwater ends up at the bottom of the ocean in various ways.

One way is the recharge of aquifers by rainfall, either in the past when sea-levels were lower (upper panel, right) or in the current day where onshore aquifers extend offshore (lower panel, right).

Another way is via glaciers with can deposit freshened groundwater offshore via basal melting and the development of sub-glacial streams and lakes.

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