The following text is an artificial-intelligence-generated, expert-checked summary of a key research study cited in a feature article from Scientific American’s July/August 2023 issue: “Found: Giant Freshwater Deposits Hiding under the Sea,” by Rob L. Evans.
You can find the study itself here: “Offshore Freshened Groundwater in Continental Margins,” by Aaron Micallef et al., in Reviews of Geophysics, Vol. 59, No. 1; March 2021.
Offshore freshened groundwater (OFG) is a valuable resource that can help reduce water scarcity in coastal areas. A recent study by Aaron Micallef of the University of Malta and his team gives an in-depth look at OFG research, updating the global database of OFG records and examining their features, how they form and what factors control them. The study also looks at the different methods used to detect and study OFG systems, such as geophysical, geochemical and modeling approaches.
The researchers discovered that most OFG bodies are found within 55 kilometers of the coast and at a water depth of 100 meters. They are mainly found in siliciclastic aquifers, which are rock formations made of broken-down minerals. The most common way these OFG bodies form is through meteoric recharge during times when sea levels are low. The study emphasizes the importance of geologic features like permeability contrast (the difference in how easily water can flow through rocks) along the top of the OFG body, the connection between permeable (allowing water to flow) and confining (blocking water flow) layers, clinoform structures (sloping layers of sediment), buried ancient river channels and faults (cracks in the Earth's crust) in controlling where OFG occurs.
The authors suggest more research to fill in knowledge gaps about OFG systems. This includes drilling campaigns to directly access microbial communities (tiny living organisms) and studying fluid flow rates and pathways (how fast and where water moves). This information could help update estimates of cell density (how many cells are present) and understanding of the connection between land-based and underwater life.
As for potential uses, OFG has been suggested as an alternative source of freshwater in coastal regions where groundwater resources are running out or becoming polluted. The study points out Cape Town, South Africa, and Melbourne and Perth, Australia, as cities where OFG has the highest potential to be used as a resource. However, there are still challenges in finding and measuring OFG, assessing its technological and economic feasibility, evaluating its environmental impact and understanding legal implications.
In conclusion, this thorough review emphasizes the importance of ongoing research on OFG systems to better understand their features, how they form, what factors control them and how they can be used to address water scarcity in coastal areas.
