Influence of Wind on Subtidal Salt Intrusion and Stratification in Well-Mixed and Partially Stratified Estuaries

Abstract

An idealized width-averaged model is employed to study the influence of wind stress on subtidal salt intrusion and stratification in well-mixed and partially stratified estuaries. We show that even in mild conditions, wind forcing can influence the estuarine salinity structure in a substantial way. By studying the role of wind forcing on dominant salt transport balances and associated salt transport regimes, we unify and clarify ambiguous observations from previous authors regarding the influence of wind stress: the response of the estuarine salinity structure to wind forcing is different depending on the underlying dominant salt transport balance, which in turn was found to determine whether wind-induced salinity shear, wind-induced modulation of the longitudinal salt distribution, or wind-induced mixing dominates. SIGNIFICANCE STATEMENT: The purpose of this idealized study is to better understand how wind influences the salinity distribution in estuaries on large time scales. This is important because a change in winds can move saline water further inland, threatening freshwater availability and the natural balance of delicate ecosystems. We clarify the sometimes ambiguous observations regarding the influence of wind on the salt distribution and highlight the importance of including average wind forcing in analyses of estuarine dynamics on large time scales.