A warm core eddy was detected south of the Brazil -Malvinas (Falkland) Confluence (BMC) region in satellite images of the southwestern Atlantic Ocean in late 2002. The structure was also sampled by in situ instruments deployed by a ship in 2 days of November 2002. An analysis of satellite data was performed to account for the lifecycle, dimension, surface temperature, surface chlorophyll concentration, surface height anomaly and displacement of the eddy since it was detached from the Brazil Current in September 2002. Satellite data were derived from several sources such as the AMSR-E, MODIS and radar altimeter. The structure lasted 64 days at south of the Brazil -Malvinas Confluence region later being re-assimilated by the Brazil Current return flow. In situ data collected during 2 days showed that the eddy was about 150 m deep, 5.5 -C warmer and 1 practical salinity unit saltier than adjacent waters. The salt anomaly associated to the eddy was estimated as 1.37 Â 10 12 kg while its heat content was 4.24 Â 10 18 J. These are typical estimates for eddies present at the BMC region. Sea surface temperature (SST), chlorophyll concentration, and sea surface height anomaly time series were analyzed for the eddy's center along its trajectory path throughout its lifetime. Mean translational velocities for the eddy during its lifetime were computed from visual interpretation and by using an adaptation of the Maximum Cross-Correlation (MCC) method on AMSR-E SST images. The overall deviation between the two methods was 26%. This suggests that the MCC method has a potential to be applied in monitoring programs to automatically account for the translational velocities of eddies in the BMC region. D

6 t/y, as it was induced by precipitation in the upper basin and materials were retained by the dams. The results exemplify that spatial differences of precipitation in the basin in relation to the location of the dam cascade generate different water run-off and material yields to the coast.

The Sargasso Sea, named due to the floating presence of Sargassum fluitans and S. natans, is usually reported for the tropical region of the Northern Hemisphere. On 14 July 2011, at 02°45’ N and 48°28’ W, samples of pelagic seaweed masses were collected by the Patrol Ship Bracuí of the Brazilian Navy. The seaweed was identified as S. natans, previously considered as of doubtful occurrence in Brazil.

Turbidity plumes of São Francisco, Caravelas, Doce, and Paraiba do Sul river systems, located along the NE/E Brazilian coast, are analyzed for their dispersal patterns of Total Suspended Solids (TSS) concentration using Landsat images and a logarithmic algorithm proposed by Tassan (1987) to convert satellite reflectance values to TSS. The TSS results obtained were compared to in situ collected TSS data. The analysis of the satellite image data set revealed that each river system exhibits a distinct turbidity plume dispersal pattern. The behavior, dimension and degree of turbidity of the São Francisco River plume have been greatly altered by the construction of a cascade of hydroelectric dam reservoirs in its hydrological basin. The plume has lost its typical unimodal seasonal pattern of material dispersion and its turbidity has decreased due to the regulation of river flow by the dams and TSS retainance by the reservoirs. In contrast, the Doce and Paraíba do Sul river plumes are still subject to seasonal pulsations and show more turbid conditions than the SF plume, as dams are less numerous, set in the middle river sections and the natural river flow has been maintained. The Caravelas Coastal System river plume is restricted to near shore shallow waters dominated by resuspension processes. During austral spring and summer when NE-E winds prevail, all plumes generally disperse southward. Short-term northward reversals may occur in winter with the passage of atmospheric cold fronts. The São Francisco and Doce river plumes tend to disperse obliquely to the coast and transport materials further offshore, while the Caravelas and Paraíba do Sul plumes tend to disperse mainly parallel to the coast, enhancing TSS retention nearshore.
O presente estudo analisa as plumas de turbidez dos sistemas dos rios São Francisco, Caravelas, Doce, e Paraiba do Sul localizados na costa NE/E do Brasil utilizando imagens Landsat e o algoritmo logarítmico para Total de Sólidos em Suspensão (TSS) proposto por Tassan (1987). Os resultados obtidos foram comparados com Total de Sólidos em Suspensão medidos in situ. A pluma de turbidez de cada sistema mostra padrões de dispersão distintos. O comportamento, a dimensão e o grau de turbidez da pluma do Rio São Francisco têm sido drasticamente alterados devido à cascata de barragens e seus reservatórios presentes em sua bacia de drenagem. Já as plumas dos rios Doce e Paraíba do Sul apresentam pulsações sazonais e maior turbidez, uma vez que as barragens nesses rios localizam-se no setor médio e mantiveram a pulsação sazonal da vazão. A pluma do sistema costeiro de caravelas permanece restrita às águas rasas dominadas por processos de ressuspensão. Durante a primavera e verão, quando os ventos de NE-E prevalecem, as plumas dos quatro sistemas se dispersam na direção sul. Durante o inverno, inversões do padrão de dispersão podem ocorrer com a passagem de frentes frias. As plumas dos sistemas São Francisco e Doce tendem a se dispersar obliquamente à costa, favorecendo o transporte de material para...

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Chlorophyll-a concentration (Chl-a) is a crucial parameter for monitoring the water quality in coastal waters. The principal aim of this study is to evaluate the performance of existing Chl-a band ratio inversion models for estimating Chl-a from Sentinel2-MSI and Sentinel3-OLCI observation. This was performed using an extensive in situ Rrs-Chl-a dataset covering contrasted coastal waters (N = 1244, Chl-a (0.03–555.99) µg/L), which has been clustered into five optical water types (OWTs). Our results show that the blue/green inversion models are suitable to derive Chl-a over clear to medium turbid waters (OWTs 1, 2, and 3) while red/NIR models are adapted to retrieve Chl-a in turbid/high-Chl-a environments. As they exhibited the optimal performance considering these two groups of OWTs, MuBR (multiple band ratio) and NDCI (Normalized Difference Chlorophyll-a Index)-based models were merged using the probability values of the defined OWTs as the blending coefficients. Such a combination provides a reliable Chl-a prediction over the vast majority of the global coastal turbid waters (94%), as evidenced by a good performance on the validation dataset (e.g., MAPD = 21.64%). However, our study further illustrated that none of the evaluated algorithms yield satisfying Chl-a estimates in ultra-turbid waters, which are mainly associated with turbid river plumes (OWT 5). This finding highlights the limitation of multispectral ocean color observation in such optically extreme environments and also implies the interest to better explore hyperspectral Rrs information to predict Chl-a.

Monthly composites of remote sensing reflectance at 555 nm wavelength (Rrs555) from ocean color imagery of the MODIS sensor onboard the Aqua platform were used to characterize the spatial and temporal variability of coastal plume in the Sofala Bank and its relation to river discharge, local rainfall, and wind speed. To achieve the objective, maps of monthly composites of Rrs555 over the Sofala Bank were inspected and statistical analysis was performed, including correlation, analysis of variance, and wavelet coherence between environmental variables and both plume area and Rrs555. Climatology of Rrs555 revealed that both plume dispersion and Rrs555 values are higher during June to December and lower during January to May. A positive correlation (r = 0.77) between wind speed and monthly time series of Rrs555, and a negative correlation between the Zambezi river discharge (r = −0.21) and rainfall (r = −0.67) with Rrs555 were found. These results suggest that variation of suspended matter in the Sofala Bank is mainly controlled by erosion and re-suspension by winds rather than the input of terrigenous matter by the Zambezi River discharge and rainfall, assuming that Rrs555 can be a valid proxy for the inorganic suspended matter. The southern portion of the Sofala Bank (i.e., near the mouths of the Pungue and Buzi Rivers) presented higher values of Rrs555 if compared to the center region near Zambezi river mouth and the northern region near Licungo river mouth. The higher Rrs555 values in the southern region might be associated with higher re-suspension rates due to increased tide mixing, dredging activities, and the shallower nature of bathymetry in the southern region. The dominance of wind in controlling the variability of suspended sediments and the eventual relatively greater contribution of Pungue and Buzi River than the Zambezi in supplying sediments could represent an evidence of weakening of Zambezi River supply of sediments, a process that might have started after damming the Zambezi Catchment.

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