Impact of Groundwater‐Surface Water Interaction on the Chesapeake Bay Density, Stratification and Mixing Under Normal and Extreme Weather Conditions

Abstract

Submarine Groundwater Discharge (SGD) is often omitted from estuarine circulation modeling systems despite its potential to alter salinity, density, and stratification. So, this study employed a one‐way coupled PARallel Flow (ParFlow)–Finite Volume Community Ocean Model (FVCOM) framework to investigate the hydrodynamic influence of terrestrially derived meteoric groundwater discharge on the Chesapeake Bay. The results show that SGD effects vary spatially and seasonally, whereas the groundwater recharge/discharge is more likely to echo the precipitation events. Submarine Groundwater Discharge effects become more significant during the low river flow conditions, especially in summer and in Middle Bay due to the high SGD to river discharge ratio. Under baseline conditions, SGD slowly enhances stratification (0%–2%) by freshening the bottom layer and sharpening the adjacent halocline where river discharges being trapped above the pycnocline barely modifies the deeper and denser layers. During Hurricane Ida, prolonged period of precipitation elevated the SGD, which resulted in a 20% salinity reduction, however, wind driven mixing dominated stratification during the storm peak and SGD‐driven bottom freshening re‐establishes stratification during post‐storm recovery. Sensitivity experiments addressing uncertainties in SGD volume show that an ideal tenfold SGD intensification produces an 8% salinity reduction and a 10% (30%) stratification enhancement (reduction) throughout the bay (shallow Upper Bay). While river discharge dominates the estuarine freshwater budget, SGD exerts a physically distinct and disproportionate secondary influence on deep‐layer density, salt intrusion, exchange circulation, and stratification, with implications for oxygen dynamics and biogeochemical cycling in this vulnerable estuary.