Geologic influence on groundwater salinity drives large seawater circulation through the continental shelf. Issue 20 (21st October 2016)

• Record Type: Journal Article
• Authors: Michael, Holly A.; Scott, Kaileigh C.; Koneshloo, Mohammad; Yu, Xuan; Khan, Mahfuzur R.; Li, Katie
• Is Part Of: Geophysical research letters. Volume 43:Issue 20(2016)
• Page Start: 10, 782
• Page End: 10, 791
• Publication Date: 2016-10-21
• Subjects: submarine groundwater discharge -- coastal groundwater -- groundwater modeling -- seawater intrusion -- geologic heterogeneity -- groundwater‐surface water interactions; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL070863
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Observations of offshore freshened groundwater and saline groundwater discharge along continental shelves have important implications for water resources, ecosystem function, and the composition of the ocean, but they cannot be explained by basic theory. We show that these independent observations are linked and result from processes that drive variable‐density groundwater flow through the spatial heterogeneity that is ubiquitous in geologic formations. We use lithologic data to develop geostatistical models that mimic the architecture of coastal aquifers. Simulation of groundwater flow and salt transport through these random realizations shows that heterogeneity produces spatially complex subsurface salinity distributions that extend tens of kilometers offshore, even at steady state. The associated density gradients drive high saline groundwater circulation rates that cannot be predicted by equivalent homogeneous models. Results suggest that these phenomena may be common along continental shelves, potentially altering estimates of ocean chemical budgets and impacting coastal water management for future generations. Key Points: Geologic heterogeneity creates offshore freshwater and complex salinity distributions in coastal aquifers Salinity gradients drive high rates of saltwater exchange along the continental shelf Conditions may be common in coastal aquifers worldwide with implications for water supply and ocean chemistry