Effect of interannual climate oscillations on rates of submarine groundwater discharge

Submarine groundwater discharge (SGD) is an important component of the coastal hydrologic cycle, affecting mixing and biogeochemistry in the nearshore environment. El Niño–Southern Oscillation (ENSO) influences rates of precipitation and groundwater recharge in many regions, including barrier islands of the southeastern U.S. coast; however, the influence of ENSO on SGD is poorly understood for this region. Here we investigate the role of ENSO in controlling recharge and SGD at interannual time scales, using modeling results for both real and generic barrier island environments. Results of our 57 year simulations show that the freshwater component of seasonally averaged SGD as well as groundwater discharge velocity, water table elevation, and submarine groundwater recharge are significantly correlated with ENSO for a real barrier island (Hatteras Island, North Carolina) and, under certain conditions, for generics. These correlations persist for lag times as great as 5 months during winter, creating anomalies of up to 35% between El Niño and La Niña conditions and suggesting that both hydrologic cycling and biogeochemical cycling in these systems are significantly influenced by ENSO.