SWAN: A surface-towed modular controlled-source electromagnetic system for mapping submarine groundwater discharge and offshore groundwater resources

What is it about?

Offshore freshened groundwater (OFG) is a vital resource for both nature and people, especially in coastal areas with high populations. However, understanding how OFG behaves beneath the seafloor has been challenging. We often rely on drilling and sampling, which have limitations. This paper introduces a new Controlled Source Electromagnetic (CSEM) system called SWAN for studying OFG and submarine groundwater discharge (SGD). Think of the SWAN system as a special tool for peering beneath the seafloor. It uses electrical signals to create high resolution images of the underground world, much like a camera captures pictures of the ground beneath the ocean. We send an electric current into the sub-seafloor from a transmitter on a boat. This current creates an electromagnetic field, akin to a signal, that travels through the ground. Sensors on the seafloor, acting as receivers, pick up this signal. By measuring how the signal changes, we can create a map of what's happening beneath the seafloor. Understanding underwater groundwater is crucial because it impacts our environment and drinking water. With the SWAN system, we can visualize where and how much OFG is. This information is invaluable for protecting our water resources and coastal ecosystems. We tested the SWAN system in the Adriatic Sea and obtained promising results. We could detect changes in the ground's electrical properties that indicated the presence of freshwater and even gas under the seafloor. This demonstrates that the SWAN system can enhance our ability to explore and manage underwater groundwater effectively. The SWAN CSEM system acts as a new set of eyes for investigating OFG and SGD. It's cost-effective, adaptable, and provides valuable insights. By employing this technology, we can gain a better understanding of the hidden world beneath the ocean and safeguard our precious water resources.

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Why is it important?

In our research, we introduce a groundbreaking approach to studying OFG and SGD using the SWAN system. What sets our work apart and makes it particularly timely are several key factors: 1. Innovative Technology: Our work showcases the development and application of the SWAN CSEM system, a novel technology that acts as a 'new pair of eyes' for exploring OFG and SGD. This innovative system allows us to gather data in a cost-effective and adaptable manner, providing unique insights into OFG dynamics. 2. Environmental Impact: Understanding OFG is more critical than ever due to its significant impact on our environment and drinking water resources. With coastal areas facing increasing challenges from rising sea levels and changing climate patterns, our research addresses a timely concern by shedding light on the availability of freshened groundwater today. 3. Resource Management: Our findings have direct implications for resource management. By mapping OFG and SGD, we offer a practical tool for safeguarding precious water resources. This aspect of our work can draw attention from policymakers and conservationists interested in sustainable resource management. 4. Promising Results: Our study in the Adriatic Sea yielded promising results, detecting changes in the ground's electrical properties that hint at the presence of freshwater and gas under the seafloor. This success demonstrates the real-world applicability of the SWAN CSEM system, making it an exciting development in the field of marine geophysics.

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