Shallow-water circulation on the northern coast of Rio Grande do Sul, Brazil: A wave-dominated system

Alongshore currents in the surf zone are formed after incident waves break. This process depends on the characteristics of the incident waves and can be altered by the wind, and to a lesser extent, by bathymetry and tide. In order to understand the behavior of the alongshore currents on the north coast of Rio Grande do Sul (Brazil), two datasets were obtained in the field. The first one was acquired during oceanographic moorings and is composed of long time series of wave data. The other database corresponded to direct measurements of vertical profiles of velocities and direction of alongshore currents in the surf zone, both simultaneously acquired for the first time in this coastal region. The analyses of these data sets enabled identification and quantification of the processes associated with incident waves and winds. Circulation by currents in the surf zone is induced by oblique incidence waves breaking as a result of radiation-stress energy flow. It was also noted that wind can influence alongshore currents to a lesser extent. The findings indicated that height and angle of incidence of waves was the main driving force of alongshore currents. A pattern has also been identified, in which waves that come from the southeast (SE) and northeast (NE) generate northeasterly and southwesterly fluxes, respectively. (C) 2021 Elsevier B.V. All rights reserved.