Reporter：Bradley A. Weymer
Location：Room 120, School of Oceanography
ZOOM Room：692 485 01401；Passcode：269186
Groundwater resources in coastal regions are facing enormous pressure caused by population growth and climate change with the recent crisis in Cape Town - a city with 4.5 million inhabitants that just escaped a total shutdown of fresh water supply - being the latest prominent example. Offshore aquifers - freshwater bodies located beneath the seafloor - have been proposed as an alternative source of freshwater. However, few studies have investigated whether offshore freshened groundwater systems are connected with terrestrial aquifers recharged by meteoric water, or paleo-groundwater systems that are no longer associated with terrestrial aquifers. Distinguishing between the two has important implications for the cycling of nutrients and trace elements to the global ocean as well as the potential use of offshore groundwater reserves to alleviate water stress for many coastal communities worldwide. Very little is known about these connections, mainly because it is difficult to acquire continuous subsurface information across the coastal transition zone. This talk explores emerging concepts and research efforts attempting to bridge this gap and focuses on near-surface terrestrial and marine electromagnetic (EM) methods as mapping tools to characterize the framework geology controls on the location and overall geometry of onshore/offshore coastal aquifers. Electromagnetic instruments are sensitive to geoelectrical contrasts between fresh (low conductivity) and saline (high conductivity) groundwater and are well equipped to advance our understanding of coastal hydrogeology across multiple spatial scales. Examples will be presented from two case studies 1) a sandy barrier island in south Texas, USA and 2) a mixed sand gravel beach along the South Island of New Zealand as a demonstration of the utility and limitations of EM methods for studying coastal hydrogeology. In this context, the fusion of geologic, geophysical, and geochemical principles in offshore aquifer research represents a new frontier in marine science and requires multidisciplinary approaches.
About the speaker：
Bradley A. Weymer is a coastal geologist by training and his main research interests focus on investigating the hydrogeology of coastal systems ranging from barrier islands, to gravel beaches, and carbonate coastlines. His area of expertise centers on marine and near-surface applied geophysics, especially electromagnetic and ground-penetrating radar methods, for solving environmental, engineering, water resources, and geologic problems. Current work includes examining if and how onshore and offshore groundwater aquifers may be used sustainably to relieve water scarcity for coastal communities around the world. Teaching interests include geology, sedimentology, geomorphology, applied geophysics, and coastal hydrogeology.