Suspended matter mean distribution and seasonal cycle in the Río de la Plata estuary and the Adjacent Shelf from ocean color satellite (MODIS) and in situ observations.

CLAUDIA G. SIMIONATO; DIEGO MOREIRA; FRANCIS GOHIN; FLORENCE CAYOCCA; MOIRA LUZ CLARA TEJEDOR

Puerto Madryn

Conferencia; 9th International Conference on Tidal Sedimentology; 2015

ASOCIACIÓN ARGENTINA DE SEDIMENTOLOGÍA

The Río de la Plata (RDP) is one of the largest and most turbid estuaries of the world, carrying a total of 160 million tons y-1 of suspended sediments. The knowledge of their spatial distribution and their scales of variability is fundamental for management and scientific reasons, but has been limited by the scarcity of observations. During 2009 and 2010, in-situ data (CTD and turbidityprofiles, and water and bottom sediment samples) were collected at 26 sites during six repeated cruises and from three fixed instruments deployed in the frame of the FREPLATA/FFEM Experiment (Figure 1). Oceanographic cruises were performed every two months approximately, and provided quasi-synoptic fields and profiles of the estuary. Water samples were analyzed for SM concentration and turbidity.Additionally, we used time series gathered at three fixed points of the RDP, providing high temporal resolution observations of waves, winds and turbidity, so as tidal observations. We complement the study with ten years of 1 km-resolution MODIS-Aqua ocean color observations in the RDP and the adjacent shelf, processed for surface SM concentration with the IFREMER algorithmfor coastal turbid waters.The aim of this work is to provide a comprehensive characterization of the annual mean suspended matter concentration distribution, to study its variability on seasonal time scale and to identify the involved physical mechanisms (Figure 2).The simultaneous use of in-situ and remote observations has allowed, for the first time, a robust characterization of the mean distribution pattern of the SM concentration and turbidity in the Río de la Plata and its variability on seasonal time scales, so as the identification of the most likely drivingprocesses. The mean surface suspended matter concentration inferred from the color remote observations using the IFREMER algorithm and their variability compare well with those derived from the in-situ observations. There is a good correspondence in the magnitude and the spatial distribution of the maxima, minima and gradients. A marked resemblance is observed between the spatial patterns of the surface SM concentration and turbidity. A linear link between both variables is observed over the whole estuary, without apparent spatial differences.