Effects of topographic variability on the formation of upwelling centers off New Jersey: A theoretical model

A theoretical wind-driven, continuously stratified coastal ocean model with varying topography is developed to examine the formation of upwelling centers in coastal oceans, such as those observed along the New Jersey coast. In this simple model an Ekman transport layer is induced by a wind-driven shear friction profile to force the coastal ocean. An analytical perturbation solution, including a component of internal Kelvin waves, is solved for the coastal upwelling system with weak alongshore-varying topography. Under uniformly upwelling favorable winds, the model solutions show that alongshore-varying topography leads to the formation of upwelling centers along the coast by increasing upwelling on the downslope sides of topographic highs and decreasing upwelling on the upslope sides of topographic highs, similar to the observed features off the New Jersey coast during summer seasons. A conservation theorem is derived that indicates the topographic variation does not change the total amount of upwelled water but redistributes it unevenly along the coast to form enhanced upwelling centers. The theory suggests that alongshore-varying topography plays an important role in controlling the formation of upwelling centers as it enhances upwelling at some locations and induces downwelling at others. In addition, the variations of the upwelling fronts are further complicated by the topographically trapped Kelvin waves.