Journal Article

Climate‐Induced Saltwater Intrusion in 2100: Recharge‐Driven Severity, Sea Level‐Driven Prevalence

Reager, J. T., Hamlington, Benjamin D., David, Cédric H., Sawyer, Audrey H., Buzzanga, Brett A., Adams, Kyra H.

2024

Overview

Saltwater intrusion is a critical concern for coastal communities due to its impacts on fresh ecosystems and civil infrastructure. Declining recharge and rising sea level are the two dominant drivers of saltwater intrusion along the land‐ocean continuum, but there are currently no global estimates of future saltwater intrusion that synthesize these two spatially variable processes. Here, for the first time, we provide a novel assessment of global saltwater intrusion risk by integrating future recharge and sea level rise while considering the unique geology and topography of coastal regions. We show that nearly 77% of global coastal areas below 60° north will undergo saltwater intrusion by 2100, with different dominant drivers. Climate‐driven changes in subsurface water replenishment (recharge) is responsible for the high‐magnitude cases of saltwater intrusion, whereas sea level rise and coastline migration are responsible for the global pervasiveness of saltwater intrusion and have a greater effect on low‐lying areas. Plain Language Summary Coastal watersheds around the globe are facing perilous changes to their freshwater systems. Driven by climatic changes in recharge and sea level working in tandem, sea water encroaches into coastal groundwater aquifers and consequently salinizes fresh groundwater, in a process called saltwater intrusion. To assess the vulnerability of coastal watersheds to future saltwater intrusion, we applied projections of sea level and groundwater recharge to a global analytical modeling framework. Nearly 77% of the global coast is expected to undergo measurable salinization by the year 2100. Changes in recharge have a greater effect on the magnitude of salinization, whereas sea level rise drives the widespread extensiveness of salinization around the global coast. Our results highlight the variable pressures of climate change on coastal regions and have implications for prioritizing management solutions. Key Points First global analysis of future saltwater intrusion vulnerability responding to spatially variable recharge and sea level rise is provided Recharge drives the extreme cases of saltwater intrusion, while sea level rise is responsible for its global pervasiveness Nearly 77% of global coastal areas below 60° north will undergo saltwater intrusion by 2100

• Publisher: John Wiley & Sons, Inc,John Wiley and Sons Inc
• Subject: Abrupt/Rapid Climate Change / Air/Sea Constituent Fluxes / Air/Sea Interactions / Aquifers / Atmospheric / Atmospheric Composition and Structure / Atmospheric Effects / Atmospheric Processes / Avalanches / Benefit‐cost Analysis / Biogeosciences / Climate / Climate and Interannual Variability / Climate change / Climate Change and Variability / Climate Dynamics / Climate Impact / Climate Impacts / Climate Variability / Climatology / Coastal aquifers / Coastal management / Coastal plains / Coastal processes / Coastal waters / Coastal zone / Coasts / Computational Geophysics / Cryosphere / Decadal Ocean Variability / Disaster Risk Analysis and Assessment / Earth System Modeling / Earthquake Ground Motions and Engineering Seismology / Effusive Volcanism / Explosive Volcanism / Freshwater / General Circulation / Geodesy and Gravity / Geological / Geology / Global Change / Global Change from Geodesy / Gravity and Isostasy / Groundwater / Groundwater Hydrology / Groundwater recharge / Hydrological Cycles and Budgets / Hydrology / Impacts of Global Change / Informatics / Inland water environment / Land/Atmosphere Interactions / Marine Geology and Geophysics / Mass Balance / Modeling / Mud Volcanism / Natural Hazards / Numerical Modeling / Numerical Solutions / Ocean influence of Earth rotation / Ocean Monitoring with Geodetic Techniques / Ocean/Atmosphere Interactions / Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions / Oceanic / Oceanography: General / Oceanography: Physical / Oceans / Paleoceanography / Physical Modeling / Policy Sciences / Radio Oceanography / Radio Science / Regional Climate Change / Regional Modeling / Research Letter / Risk / Saline water / Saline water intrusion / Salinization / Salt water intrusion / Saltwater intrusion / Sea level / Sea Level Change / Sea level changes / Sea level rise / Sea Level: Variations and Mean / Seawater / Seismology / Solid Earth / Subsurface water / Surface Waves and Tides / Theoretical Modeling / Tsunamis and Storm Surges / Volcanic Effects / Volcanic Hazards and Risks / Volcano Monitoring / Volcano Seismology / Volcano/Climate Interactions / Volcanology / Water Cycles / Watersheds