Driving while under the influence: pumping-driven circulation under the influence of regional groundwater flow

摘要

Regional submarine or ambient groundwater discharge (AGD) along sea coasts interacts with current-driven interfacial pumping of seawater through shallow sediments,. We use numerical simulations to investigate this interaction for a turbulent current flowing over dune topography. AGD reduces the extent of the current-topography driven interfacial exchange zone (IEZ) and may prevent its development when AGD overpowers interfacial exchange. Under upwelling-AGD conditions (upward flux of deep ground-water into the water-column), the IEZ is centred on the stoss face of bedforms and AGD occurs near the crest, Under downwelling-AGD conditions (downward flux of seawater deep into the aquifer), the IEZ forms around the crest and water infiltrating along the stoss face into the sediments does not return to the sediment-water interface The IEZ depth, flux and residence time are functionally related to current Reynolds number (Re). For example, the IEZ water residence time, which follows a power-law distribution, is larger at lower current Re.