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An integrated hydrodynamic and Lagrangian transport model was used to estimate the average residence time in the Bahia Blanca estuary (Argentina) for wind conditions of different seasons. The Bahia Blanca estuary consists on an elongated system of meandering bays surrounded by tidal flats and salt marshes where the tide is the principal forcing. Modelling results show that both the tidal amplitude and wind forcing affect significantly the residence time, since river discharge is very low. An increase in the wind intensity along the bays main axis causes a considerable increase in the intensity of the residual current and thus a modification of the average residence time over the model domain. In all seasons, the overall residence time ranges from 12 to 77 days. The values allow establishing a hydrodynamic performance for each of the estuary sectors over each seasonal period. These findings provide useful information to quantify the transport processes on the different sectors of the Bahia Blanca estuary necessary to understand temporal and spatial variations.

The Brazil–Malvinas Confluence Zone (BMCZ) is characterized by high environmental variation, which could be reflected in several optical types of water, from one containing only phytoplankton and sea water to other optically more complex. In this paper, we analyze the spatio-temporal variability of the Chlorophyll-adetected by the ocean color sensor (CHLAsat) in BMCZ in order to understand its environmental variability. We use the MODIS-Aqua CHLAsatmonthly composites imagery from 2002 to 2015, and applied two statistical methods: the correlogram-based robust periodogram to identify, over a broad spectrum of temporal, the most significant periodicities, and the pixel gradient distribution to study the spatial-temporal gradients within the BMCZ and variations over the continental shelf and coastal waters. Our results point out to the predominance of the annual cycle over most of the investigated area, although an area from latitude 37°S in direction NE, alongshore of Uruguay to Brazil, evidences interannual periodicities, possibly related to variations in the discharge of the Rio de la Plata associated with the El Niño phenomena. The ocean color spectroradiometric signature in terms of pixel gradient presents a relatively high variability (∼0.0 to 0.65mgm−3); in particular the high values of the pixel gradient correspond to saline front of the estuarine system of Rio de la Plata, and to the strip of the platform that extends along the isobaths of 80m (coast of Uruguay), especially in the center and south of the study area.

The collision of the warm and salty southward flowing Brazil Current and the cold and relatively fresh northward flowing Malvinas Current produces a strong frontal zone known as the Brazil–Malvinas Confluence Zone (BMCZ). This is featured by intense presence of eddies and meanders and is one of the most energetic areas of the world oceans. We apply the statistical method of Fisher–Shannon (FS) to the time series of sea surface temperature, derived from the satellite Advanced Very High Resolution Radiometer (AVHRR) imagery, acquired from 1984 to 1999. The FS method consists of the joint application of Fisher information measure (FIM) and Shannon entropy (SE), measuring respectively the degree of organization and the disorder of a system. Our findings indicate that the FS method is able to locate very clearly the BMCZ, which corresponds to the less organized and more disordered area within the area of confluence between the Brazil and Malvinas Currents.

Abstract: By using the recent method of the visibility graph, three time series of oceanic tide level in central Argentina were investigated. The degree distributions show a rich structure; in particular the maximum is due to the main periodic oscillations at 24hours and 12hours and higher harmonics. The degree distributions of the residuals (obtained removing from the original signals the cyclic components) suggest that the local effects, linked with the particular coastal conditions of the sites, are discernible for the degree k <20, while the global effects, linked with linked with the more general and common atmospheric forcing and ocean current conditions, are visible for k >100. Although a relationship between the spectral exponent α and the exponent of the degree distribution γ of tidal signals can be recognized, this cannot be simply stated due to the very rich and complex structure of time dynamics of tides. The present study, even if still preliminary, show the importance of the visibility graph method in investigating the complex time dynamics of observational and experimental signals. [Copyright &y& Elsevier]