Remotely sensed seasonal dynamics of an estuarine plume in the coastal zone of El Rincón system (Southwestern Atlantic Ocean)

In this work we analyzed 18 years (2003–2021) of MODIS-Aqua daily images and multi-annual monthly mean turbidity maps to provide a comprehensive characterization of seasonal patterns of turbidity in the transitional area between the mouth of the Bahía Blanca Estuary and the adjacent inner shelf (El Rincón coastal system, Argentina). Field measurements collected in the study area were combined with MODIS data processed under different schemes of atmospheric correction before turbidity retrieval. Then, an Empirical Orthogonal function (EOF) analysis was used to assess the temporal patterns of turbidity and their regional variability over the inner shelf. Through a Generalized Linear Model (GLM), changes in the turbidity plume were further associated with environmental forcing (i.e. tides, winds and precipitation) controlling the seasonal dynamics. A strong gradient of decreasing turbidity from the northeast (close to the estuarine region) to the southwest (coastal region) was detected, while a major spatial pattern of annual variability, characterized by decreasing seasonality from northwest to southeast was defined. According to our results, the frequency of northwest wind direction and the impact of the wind mixing are considered as primary factors that shape the seasonal variability of turbidity with a strong winter dominance of largest plume events. The results found in this study are key to understanding the general dynamics of biological activity in the regional waters and the implications that climate variability might have on this complex ecosystem.