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A very high-resolution modelling configuration was created for the estuary of Baia de Todos os Santos – BTS, Brazil (300 to 400 m), and adjacent coastal waters (600 to 1200 m). The adoption of a multi-corner domain approach allowed the variable spatial resolution required to resolve the shelf, the bay and their interactions. Seven years were simulated using realistic oceanic, atmospheric and riverine forcing. Model validation was done against observations showing the model skill to reproduce the thermohaline field, the tidal currents, as well as the variability of the free surface at tidal and sub-tidal time scales. The results provide the first representation of the tidal wave propagation along the bay, in terms of maps of amplitudes, phases and ellipses of the barotropic currents for the main tidal constituents. By analysing the residual currents at different depths, in terms of averages over the simulation period, several prominent structures were identified and named: (i) Salvador eddy (up to 0.2 m s−1); (ii) St Antonio current (up to 0.45 m s−1); (iii) Salvador current (up to 0.5 m s−1); (iv) Itaparica eddy (up to 0.2 m s−1); (v) Ilha dos Frades southern eddy (up to 0.1 m s−1); and (vi) Ilha dos Frades northern eddy (up to 0.2 m s−1). The model set-up proved to be highly efficient and robust simulating the BTS shelf-estuary region and such an approach may be suitable to other estuarine systems.

Near-inertial oscillations (NIO) are intermittent motions with a frequency close to the inertial frequency and represent an important fraction of the energy to the currents in the upper ocean. Based on hourly velocity records at the shelf break covering the top 50 m of the water column in 5 locations and one additional location at Cabo Frio upwelling system (22° S) covering the top 200 m of water column with hourly velocity and temperature measurements, the aim of the present study is to characterize NIO along the Brazilian continental shelf break (16° S–31.5° S) describing the spatial variability of inertial energy in the mixed layer and the role of the NIO in the high-frequency hydrodynamic. The sites between 31.5° S and 28.5° S were those that revealed more near-inertial energy and higher relative importance of the near-inertial band for the variance of the currents (29% and 31%, respectively). This is associated with the proximity between the inertial frequency and the sea breeze frequency in this region, which delimits an inertial resonance area for the NIO around 30° S. The near-inertial currents between 31.5° S and 23.5° S range between 30 and 50 cm s−1 and decrease toward the locations at lower latitudes, where the range is between 5 and 25 cm s−1. Vertical shear of the order of 10−3 s−1 was reached during NIO events between 31.5° S and 23.5° S in the upper layer of the ocean (mixed layer, seasonal thermocline, and upper permanent thermocline) and can play an important role in the vertical mixing along the Brazilian continental shelf break. The NIO events analyzed at Cabo Frio upwelling system exhibited a mean duration of around 7.6 days, upward vertical phase velocity of the order of 10−1 cm s−1, vertical wavelengths of the order of 102 m, and vertical downward group velocity of the order of 10−2 cm s−1. Nevertheless, the magnitude of the vertical propagation of energy and duration of the events demonstrate the importance of NIO as a source of kinetic energy to the ocean interior.

A bacia do Rio Parana e uma das bacias hidrograficas mais importantes para o setor de energia no Brasil e, com a bacia do Rio Paraguai, faz parte da segunda maior bacia hidrografica da America do Sul, a bacia Platina. Uma analise da precipitacao sobre as bacias do Rio Parana e do Rio Paraguai no seculo XXI e realizada utilizando modelos climaticos para avaliar mudancas no ciclo hidrologico. Alem da precipitacao, este estudo utiliza uma reanalise global na avaliacao da habilidade de tres modelos climaticos globais em representar os padroes climatologicos da circulacao de verao da America do Sul que afetam o ciclo hidrologico nas duas bacias. As integracoes climaticas utilizadas estao disponiveis para o periodo historico, 1975-2004, e para as projecoes, 2041-2070 e 2071-2100. As projecoes climaticas utilizadas neste estudo sao forcadas pelo Representative Concentration Pathway (RCP) 8.5, que e a trajetoria mais extrema do Fifth Phase of the Coupled Model Intercomparison Project. A regionalizacao, que permite analises mais detalhadas nas bacias, foi feita usando o RegCM4 no âmbito do Coordinated Regional Downscaling Experiment project. O RegCM4 usou condicoes iniciais e de contorno provenientes dos seguintes modelos globais, tambem analisados neste estudo: o ESM2M do Geophysical Fluid Dynamics Laboratory; o ESM-MR do Max Planck Institute; e o HadGEM2 do Hadley Center. Para o periodo historico, HadGEM2 e ESM2M concordam melhor com a reanalise global na representacao dos padroes atmosfericos na America do Sul do que o ESM-MR. A regionalizacao do HadGEM2 apresenta menores erros na precipitacao do que as demais regionalizacoes em comparacao com as observacoes nas bacias. Quanto a diferenca entre precipitacao e evaporacao, os resultados mostram pouca alteracao no clima futuro para o mes de janeiro, exceto no sudoeste da bacia do Rio Parana na regionalizacao do ESM-MR.

Ocean-estuary exchange variability was studied from 2008 to 2014 at a low latitude coastal plain estuary, Todos os Santos Bay, Brazil, near 13°S. Wind data from Climate Forecast System Reanalysis (CFSR) were used to complement the results of a high-resolution regional ocean model, ROMS. Volume exchange occurred under two distinct circulation patterns, namely Circ + and Circ − , that matched the down-estuary (spring/summer) and up-estuary (autumn/winter) wind regimes respectively. Circ + promoted water-column stratification, while Circ − lasted longer, induced more volume exchange, and reversed the estuarine circulation. In addition, a clockwise lateral circulation (looking into the estuary) occurred during Circ + , whereas a counterclockwise lateral circulation was observed during Circ − . Connectivity was observed between Jaguaripe River and Todos os Santos Bay entrance. Increases in Jaguaripe River discharge, in conjunction with up-estuary winds, promoted a northward advection of the river plume toward the main entrance of the estuary, creating a lateral density gradient over Todos os Santos Bay' western shoal. Our results demonstrate that findings about estuarine circulation at higher latitudes are applicable to low latitude estuaries when dynamical depth and/or basin's width indicate that Earth's rotation is relevant.

Upwelling and uplift events from 2008 to 2012 were analyzed at the South Equatorial Current bifurcation region and in the Salvador Canyon near 13°S. Wind data from Climate Forecast System Reanalysis (CFSR) were used to complement the results of a high-resolution regional ocean model. Upwelling and uplift events occurred predominantly during spring and summer. Previous studies have suggested upwelling implications for fisheries and fish diversity in the region. Uplift events were, on average, longer than upwelling events. Spatially, the strongest events were found over the adjacent shelf of Todos os Santos Bay and Salvador Canyon. This was also the region with the most frequent events. Analysis of forcing mechanisms revealed that wind-driven upwelling, mainly due to upward Ekman pumping, is dominant, with current-driven upwelling providing an additional contribution. Connectivity between Salvador Canyon and Todos os Santos Bay upwelling processes was observed in 20 events, preferentially during the austral summer. This connectivity was linked to a northward coastal undercurrent, which, in turn, advected upwelled/uplifted water from the canyon to the bay-adjacent shelf area. Connectivity occurred under two conditions: i) intense canyon upwelling and ii) low influence of the Brazil Current flow on the shelf. The results of this study demonstrate that wind-driven upwelling contributes directly to the connectivity phenomenon, whereas Brazil Current encroachment inhibits this process. Hence, the results shown herein are widely applicable to upwelling regions under the influence of Western Boundary Currents and/or submarine canyons where upwelling may occur.

This study investigates the propagation of coastal trapped waves (CTWs) along the Brazilian continental shelf between 34°S and 11°S using in situ data combined with the outputs from a high-resolution ocean simulation with HYCOM. The CTWs generation area covers a wide region ranging from the Patagonian shelf to the southern Brazilian shelf. The spectral analysis of coastal sea level series between 54°S and 10.5°S shows three bands of high energy associated with periods from 5 to 12 days, 15–22 days, and 25–40 days. The energy of the CTWs decreases along their propagation for all frequency bands, showing a drastic reduction north of 22°S, due to abrupt variations in the width and depth of the continental shelf between Tubarao Bight and Abrolhos Bank. Their phase speed propagation varies along the coast, being faster (>25 m/s) in the southernmost region (between 42°S and 41°S), reaching ~11 m/s north of 41°S, and reducing to ~3 m/s further north (equatorward of 24°S). The free Continental Shelf Wave theory supports the notion that the intense deceleration north of 24°S can be explained by the narrowing of the continental shelf. The stratification parameter indicates that the Brazilian continental shelf has a barotropic response to wind-generated disturbances.

Estuaries may have ideal technical conditions for tidal energy conversion: strong currents and proximity to the coast and urban/industrial infrastructures. This is the case of the estuary Baia de Todos os Santos, for which a numerical tidal potential density assessment was done. This study used a high resolution numerical configuration of the ocean model ROMS forced with realistic surface and lateral forcing, as well as with tides and river discharges into the bay. Strong currents were found along the main axis of the bay, particularly at the centre and left side of the bay’s main entrance, and for a considerable time fraction. In these regions, speeds higher than 1 m s −1 were found during about 30% of the time leading to a power density around 1300 W m −2 at the surface layer, reaching peaks higher than 2500 W m −2 . The energetic flow at the left side of the inlet is affected by a remarkable sand ridge, the St. Antonio Bank, which intensifies the flow between the shoal and the coast. Operation time versus tidal power (OTP) diagrams for the bay’s entrance show that even with a sharp reduction of operation time (50%) it is still possible to extract a high portion (95%) of the total power density available. Using tidally filtered time series of speed and power density, three important oscillations were found: fortnight associated with M 2 +S 2 spring-neap cycle; semi-annual caused by the S 2 +K 2 interference and responsible for about 1/4th of the total power density; and annual oscillation related with external forcings. The residual flow contributes substantially to the total power density. This contribution is however highly spatially variable, reaching at the bay’s entrance 33% and 17% at the isobaths 10 and 25 m, respectively (at sites separated 2.5 km). Besides the bay’s entrance, some regions inside the bay were identified as potentially interesting for tidal stream energy, but its study requires observations and also additional developments in the modelling configuration.

International audience; Integration of observations of the coastal ocean continuum, from regional oceans toshelf seas and estuaries/deltas with models, can substantially increase the value ofobservations and enable a wealth of applications. In particular, models can play a criticalrole at connecting sparse observations, synthesizing them, and assisting the design ofobservational networks; in turn, whenever available, observations can guide coastalmodel development. Coastal observations should sample the two-way interactionsbetween nearshore, estuarine and shelf processes and open ocean processes, whileaccounting for the different pace of circulation drivers, such as the fast atmospheric,hydrological and tidal processes and the slower general ocean circulation and climatescales. Because of these challenges, high-resolution models can serve as connectorsand integrators of coastal continuum observations. Data assimilation approachescan provide quantitative, validated estimates of Essential Ocean Variables in thecoastal continuum, adding scientific and socioeconomic value to observations throughapplications (e.g., sea-level rise monitoring, coastal management under a sustainableecosystem approach, aquaculture, dredging, transport and fate of pollutants, maritimesafety, hazards under natural variability or climate change). We strongly recommendan internationally coordinated approach in support of the proper integration of globaland coastal continuum scales, as well as for critical tasks such as community-agreedbathymetry and coastline products.

The Brazil Current (BC) is the Western Boundary Current of the South Atlantic subtropical gyre, the dominant dynamic feature in the South Atlantic Ocean. The importance of this current lies in that it is the main conduit of subtropical waters to higher latitudes in the South Atlantic Ocean. This study assesses the structure and variability of the BC across the nominal latitude of 22° S using data from the high-density eXpendable BathyThermograph (XBT) AX97 transect and from three numerical ocean models with data assimilation. This XBT transect was implemented in 2004 and represents one of the longer-term monitoring systems of the BC in existence. The goal of this work is to enhance the understanding of the temporal and spatial variability of the ocean dynamics in the southwestern South Atlantic Ocean by using a suite of hydrographic observations and numerical model outputs. In the present work, 37 XBT transect realizations using data collected between 2004 and 2012 are used. Daily outputs covering the same time period are evaluated from Hybrid Coordinate Ocean Model with the Navy Coupled Ocean Data Assimilation (HYCOM-NCODA) with a 1/12° horizontal resolution, and GLORYS2V3 and FOAM, both with a 1/4° horizontal resolution. These Ocean Forecasting and Analysis Systems (OFAS) are able to capture the mean observed features in the 22° S region, showing a BC core confined to the west of 39° W and an Intermediate Western Boundary Current between the depths of 200 and 800 m. However, the OFAS tend to overestimate the mean BC baroclinic volume transport across the AX97 reference transect and underestimate its variability. The OFAS show that the coastal region between the coastline and the western edge of the AX97 transect plays an important role in the mean BC total transport, contributing to up to 23 % of its value, and further that this transport is not sampled by the XBT observations with its current sampling strategy. In order to understand the variability of the BC, a statistical classification of the BC is proposed, with the identification of three different events: weak, intermediate, and strong.

The use of Expendable Bathythermographs (XBTs) is widespread throughout the world’s oceans. 15 XBT high-density transects are located only in the Atlantic Ocean. However, the only transect that exclusively monitors the Brazil Current (BC) is the NOAA/AOML AX97 transect, running from Rio de Janeiro to Trindade Island. The BC is the Western Boundary Current linked to the circulation of the South Atlantic subtropical gyre. Surface velocity field based on the AX97 XBT data reference transect and two different altimetry datasets (AVISO and ATOBA) are compared with the objective of assessing the impact of different horizontal resolution altimetry products on averaged BC dynamical features. Furthermore, a sensibility study is performed considering different approaches to estimate BC volume transports. Data from 43 AX97 cruises, covering the period from Jan/2004 to Dec/2013 were used. AVISO (ATOBA) data are daily (weekly) and present a spatial resolution of 1/4° (1/12°). AX97 geostrophic velocity values were calculated based on XBT data using the isopycnal of σ θ = 26 . 8 kg/m3 as the reference level of no motion, whereas the altimetry surface geostrophic velocities were obtained based on maps of absolute dynamic topography. About 80.5% (74.4%) of the time, at least one altimetry dataset observed the BC core at AX97 region. ATOBA dataset presented a better performance if compared to AVISO when the BC is highly unstable. Also, in coastal areas, where the flow frequently changes direction, a high-resolution altimetry product (ATOBA) tends to represent the horizontal structure of the BC better than AVISO, where BC horizontal pattern is smoother. Finally, the merge between AX97 data and altimetry datasets presented some inconsistencies when surface currents are in opposite directions. It is recommended to combine AX97 data with another type of data acquired in deeper regions, where near-zero velocities will propagate a smaller error along the water column.

River runoff into the continental shelf affects the coastal environment in many ways: from sediment input and marine sediments resuspension to meso-scale eddies formation in case of higher river discharges. Therefore, for ocean modeling is crucial to understand the seasonal and interannual river runoff variability. Brazil stands out when it comes to riverine discharge, since 6 out of the 50 largest rivers flows within the country limits. Here, a compilation of all river discharge data provided by the Brazilian National Water Agency resulted in the identification of 97 exorheic rivers (with time series longer than 15 years), including 10 unmonitored ones which had climatologies estimated by the proposed methodology. This compilation took a considerable effort, as streamflow stations were often far from the discharge location. It was also necessary to overcome the challenge associated with the Brazilian climate heterogeneity in order to apply the regionalization method. The riverine input into the ocean was estimated at the mouth of the rivers, with the overall discharge analysis taking into consideration a division of the Brazilian Continental Shelf in five sectors. These results analyzed here are also made available for public use. Overall, the Brazilian northern continental shelf receives about 95% of the total annual river runoff (212,148 m3 s−1), followed by the northeastern continental shelf with 1.5% (3345 m3 s−1), the eastern continental shelf with 1.4% (3097 m3 s−1) and the southern continental shelf with about 1.3% (2997 m3 s−1). The southeastern continental shelf receives only 0.8% of the total discharge (1909 m3 s−1). Throughout the year, the major river discharges were observed from summer to winter months, following the different climate and precipitation patterns along the country. The interannual variability of the discharges was assessed, also looking at similarities regarding both El Nino Southern Oscillation and Pacific Decadal Oscillation.

Upwelling events observed from the years 2003 to 2011 were analyzed. Our focus was on the Abrolhos–Campos region (ACR, 15°S–23°S), which is located along the Brazilian Margin and influenced by a western boundary current, the Brazil Current (BC). Satellite sea surface temperature, National Centers for Environmental Prediction (NCEP) and Global Forecast System (GFS) wind data were used to complement the results of a high-resolution regional oceanic model to investigate the occurrence of and the mechanisms responsible for intense upwelling events in this region. These events were more frequent from 20°S to 23°S. Over 90% of the identified upwelling events were influenced by favorable wind stress. Surface Ekman transport was found to be more important for the region from Prado (17°S) to Marataizes (21°S), whereas upward Ekman pumping played a more important role from 22°S to 23°S. Current-driven upwelling processes associated with the location of the BC as well as its velocity and meso-scale activity were also analyzed. The results showed that these mechanisms are highly influenced by the local topography. Topographic effects exerted via the acceleration of the BC are more obvious in the southern ACR, while in the Prado region, BC cyclonic meanders tend to be more relevant. Moreover, eddy-driven upwelling increases in the southward direction after the passage of the Vitoria-Trindade Ridge (20°S), an important submarine chain, which acts to constrain and modulate the southward flow of the BC.

On 5 November 2015, the Fundao tailings dam collapsed and its content first reached River Doce and then the Atlantic Ocean by 22 November. This study focuses on the oceanic time and space patterns of river discharge dispersion. By using an ocean model together with nLw(555) and RGB images from MODIS sensors, the river plume was followed for 2 months after the arrival of the tailings at the ocean. The results show the huge effect of this accident and reveal that riverine waters may have dispersed hundreds of kilometres, reaching regions as far as the shelf in front of the city of Rio de Janeiro. The movement of the freshwater was essentially to the south in accordance with the seasonal wind regime. Episodic frontal systems, leading to wind reversion, and oceanic mesoscale features contribute to the offshore dispersion of the plume. The region more often in contact with the riverine waters was located at the inner shelf between the river mouth and the city of Vitoria, turning to the outer shelf and shelf break at lower latitudes.

The circulation at the Eastern Brazilian Shelf (EBS), near 13°S, is discussed in terms of the currents and hydrography, associating large-scale circulation, transient and local processes to establish a regional picture of the EBS circulation. The results show that the circulation within the continental shelf and slope region is strongly affected by the seasonal changes in the wind field and meso/large-scale circulation. Transient processes associated to the passage of Cold Front systems or meso-scale activity and the presence of a local canyon add more complexity to the system. During the austral spring and summer seasons, the prevailing upwelling favorable winds blowing from E–NE were responsible for driving southwestward shelf currents. The interaction with the Western Boundary Current (the Brazil Current), especially during summer, was significant and a considerable vertical shear in the velocity field was observed at the outer shelf. The passage of a Cold Front system during the springtime caused a complete reversal of the mean flow and contributed to the deepening of the Mixed Layer Depth (MLD). In addition, the presence of Salvador Canyon, subject to an upwelling favorable boundary current, enhanced the upwelling system, when compared to the upwelling observed at the adjacent shelf. During the austral autumn and winter seasons the prevailing downwelling favorable winds blowing from the SE acted to total reverse the shelf circulation, resulting in a northeastward flow. The passage of a strong Cold Front, during the autumn season, contributed not only to the strengthening of the flow but also to the deepening of the MLD. The presence of the Salvador Canyon, when subject to a downwelling favorable boundary current, caused an intensification of the downwelling process. Interestingly, the alongshore velocity at the shelf region adjacent to the head of the canyon was less affected when compared to the upwelling situation.

Based on a vast set of in situ data, a first comprehensive overview of the oceanographic characteristics of Ba ´ia de Todos os Santos (BTS) is provided. BTS is the second largest coastal bay in Brazil (maximum area of 1223 km 2 and average depth of 9.8 m), and is located in the northeast Brazil, in the vicinity of Salvador city. The circulation inside the bay is mostly tidally driven and does not vary significantly throughout the year. On the other hand, the wet (winter) and dry (summer) seasons does alter significantly the distribution of water properties inside the BTS. During summer, the waters inside the bay have oceanic characteristics, with Tropical Water (TW) penetrating along the whole region, except for the mouth of Rio Paraguacu. The water temperature inside the bay is higher than in the coastal zone, and variations can be up to 3 ◦ C, reaching a maximum of nearly 30 ◦ C. During winter, with the increase of freshwater inflow, salinity variations of about 4 are observed between the innermost stations inside BTS and the adjacent coastal region. Salinity values inside the bay can be as low as 32.3, inhibiting the penetration of TW into the BTS, which is totally occupied by a locally formed Coastal Water (CW). An evaluation of the flushing time is also provided and shows that during summer, a 60-fold increase can be observed compared to winter (38 days). While the circulation does not vary seasonally inside the bay, the associated inner shelf is characterized by two different scenarios. During summer, the upwelling favorable easterlies drive a southwestward flow, while during winter the more frequent occurrence of cold fronts (southerly winds) tend to reverse the circulation.

The Camamu bay (BCM), located at central coast of Bahia, is a pristine region which has been the target of oil and gas activities that could put in jeopardy the whole...RESUMO. A baía de Camamu (BCM), localizada na porção central do litoral bahiano, é uma região considerada intocada que vem sendo alvo de atividades de exploração de óleo e gás, que...

The Abrolhos Bank is part of the so-called Eastern Brazilian Shelf and is an area of high ecological and economic importance. The bank supports the largest and richest coral reefs in the South Atlantic and the largest rhodolith bed in the world. The spatial and seasonal variation of phytoplankton concentration, however, and the dynamic processes controlling that variability have remained poorly known. The present study investigates the seasonal and spatial distributions of chlorophyll-a (Chl-a) and water conditions by analyzing nine years (2003-2011) of level-3 Moderate-resolution Imaging Spectroradiometer (MODIS) derived Chl-a, National Centers for Environmental Prediction (NCEP)/ETA model-derived winds, NCEP model-derived heat fluxes, thermohaline and velocity results from the Hybrid Circulation Ocean Model (HYCOM) 1/12o assimilated simulation. The results show that low/high concentrations occurred in austral spring-summer (wet season)/autumn-winter (dry season), with the highest values observed in the northern portion of the Abrolhos Bank. The typical meteorological and oceanographic conditions during austral summer favor the development of strong stratification. These conditions are 1) N-NE winds that favor an upwelling-type Ekman circulation; 2) coupling between the open ocean and the continental shelf through the western boundary current, which promotes cooler subsurface water to rise onto the shelf break; and 3) positive net heat flux. In contrast, the S-SE winds during autumn are in the opposite direction of the predominant current system over the Abrolhos Bank, thus reducing their speed and inducing an inverse shear. The warmer ocean and a somewhat cool and dry atmosphere promote the evaporative cooling of the surface layer. The above processes drive mixed layer cooling and deepening that reaches its maximum in winter. The blooming of phytoplankton in the Abrolhos Bank waters appears to be regulated by changes in the mixed layer depth, with Chl-a levels that start to increase during autumn and reach their peak in June-July.

The oceanic features in the eastern and southeastern brazilian shelf/slope south of 13S is investigated using ROMS (Regional Ocean Model System). The model integration was 9 years and it was forced with: i) 6-hourly synoptic atmospheric data from NCEP; ii) initial and boundary conditions from OCCAM (Ocean Climate Circulation Advanced Modelling) monthly mean climatology and iii) tidal forcing from TPXO 7.1 global data set. The model results were compared with observations, which consisted in thermodynamic MDL (Mixed Layer Depth) climatology, satellite data, measurements from tide gauges along the shelf and currents measurements values from literature. The simulated currents represented well the BC (Brazil Current)-IWBC (IntermediateWestern Boundary Current) System. The BC - IWBC system at 22S cross-shelf section, where the mean alongshelf velocity represents our simulation capability of reproducing the western boundary currents, showed poleward BC and a opposing IWBC. At this section, the BC velocity core is in 50 m with 0.41 m.s−1 and the IWBC core around 800 m with 0.15 m.s−1.

During the austral winter of 2008, thousands of penguins traveled to low latitudes along the South Atlantic coast of South America. The atmospheric and oceanic conditions from April to July 2008 may account for the penguins' unusual geographic distribution. During that period, South Atlantic coastal waters were cooler; the wind anomalies had northward and onshore components; the ocean's coastal region presented northward currents that favored the penguins to travel toward lower latitudes. This anomalous climate regime resulted from extreme meteorological frontal systems that occurred mainly during June 2008. Three consecutive extreme midlatitude cyclones produced strong wind shear that resulted in the northward oceanic flow along the South American eastern shoreline favoring the penguins to be spotted in northern tropical waters.

This study presents a comparative analysis of several theoretical oil spill scenarios occurring in the vicinity of the Abrolhos Reefs, a preservation area located off the Brazilian east coast. The following petroleum blocks were considered in the study: BM-CUM-1, BM-CUM-2, J-M-259 and ES-M-418, to verify the effect of the tide on the oil spreading on the continental shelf in the eastern Brazilian. The probabilistic oil spill simulations were carried out for 30 days and considered an oil of intermediate API (American Petroleum Institute) type. The simulations were performed by the OSCAR (Oil Spill Contingency and Response) model which was fed by synoptic wind data and hydrodynamic data simulated by the POM (Princeton Ocean Model) model. Two distinct seasonal scenarios were studied: the austral winter and the austral summer of 1989 and the results were discussed in terms of seasonal variability caused by the winter/summer winds and differences in mesoscale instabilities. The effect caused by tidal currents was analyzed through the comparison between simulations with and without the tides. It was concluded that the tide strongly influenced the probabilistic results of fate of oil in the spill scenarios. Many factors have influenced this fate of the spreading of oil in the absence of supra-inertial processes, such as the location of the spill, the behavior of the prevailing winds and tides in the region. The tide absence in the hydrodynamic data did not found the worst case scenarios of the spill in simulations in blocks BM-CUM-1, BM-CUM-2 and J-M-259, mainly in summer with use of intermediate oil, underestimating the real scenarios of spill. O presente estudo teve por objetivo realizar modelagens de diferentes cenários de derramamentos de óleo em blocos de petróleo (BM-CUM-1, BM-CUM-2, J-M-259 e ES-M-418) em áreas adjacentes ao Recife de Abrolhos, a fim de verificar o efeito da maré no espalhamento do óleo na plataforma leste brasileira. Foram realizadas simulações de 30 dias de derramamento de óleo de grau API (American Petroleum Institute ) intermediário, utilizando como ferramenta o modelo OSCAR (Oil Spill Contingency and Response), sendo alimentado com dados hidrodinâmicos simulados pelo modelo POM (Princeton Ocean Model ) e dados de vento sinótico simulados pelo modelo ETA, o qual foi alimentado com dados de reanálise do NCEP. Os períodos abordados foram o inverno e o verão do ano de 1989 e os resultados foram discutidos em termos das variações de intensidade e direção do espalhamento causado pelo vento sinótico de cada estação, assim como pelos processos de mesoescala e pela maré. O efeito causado pela maré foi analisado através da comparação de simulações com e sem maré. Concluiu-se que a maré influenciou fortemente nos resultados probabilísticos de destino do óleo nos cenários de derramamento. Muitos fatores mostraram influenciar nesse destino do espalhamento do óleo com a ausência dos processos supra-inerciais, como a localização geográfica do derramamento, os ventos predominantes e o comportamento da maré na região. A ausência da maré nos dados hidrodinâmicos não permitiu encontrar os cenários de pior caso de derramamento em simulações nos blocos BM-CUM-1, BM-CUM-2 e J-M-259, principalmente no verão com a utilização de óleo intermediário, subestimando os cenários reais de derramamento.

The dynamics of a large (∼ 22 km wide) and deep (∼ 600 m deep) submarine canyon was investigated using data from three ADCP transects perpendicular to the coast: i) at the canyon axis and ii) at the northern and southern adjacent shelves, as well as high resolution CTD data collected at various hydrographic stations located in each transect. In order to represent the seasonal cycle, the region was seasonally covered during a whole year. Preliminary results show that the wind forcing exerted a great influence on the coastal circulation at the northern and southern canyon’s adjacent shelves. At the canyon’s head, a topographically trapped cyclonic circulation was observed, being intensified during downwelling favorable winds. Its cyclonic circulation affected the coastal circulation at northern adjacent shelf, which showed a surface reversal in comparison to the preferential shelf flow. At depths around 200 m, and below the canyon rim, the flow field was also disturbed by the canyon topography. Vertical hydrographic profiles confirm the strong wind influence to the local dynamics. During the winter season a deeper isothermal layer (∼200 m deep) was observed, caused by the intense mixing promoted by stronger winds, due to the influence of cold front passages.Copyright © 2008 by ASME

The coastline of Bahia State, Brazil, in the eastern sector of the northeastern region of Brazil, has a total of 20 beaches, 14 of which are located on theopen sea (Atlantic Ocean), while the others are sheltered in the Todos os Santos Bay. Many of these beaches have been or are currently being affected by episodes ofsevere coastal erosion which are intrinsically related to both anthropogenic and natural processes. This study aimed to use statistical analyses of information and data,such as photos, texts from local newspapers, synoptic maps and reanalysis data from the National Centers for Environmental Prediction to identify severe erosion eventsrelated to meteorological tides on the Salvador coastline during the period from 1965 to 2006. The results show that most erosion events appear to be associated withthe occurrence of meteorological tides and have great destructive potential. We found that the combination of i) the occurrence of spring tides with ii) the arrival of coldfronts and/or coupling of a high pressure system with a trough in the lower levels of the atmosphere and iii) winds predominately from S and SE, that through Ekmantransport, promotes pilling up of water against the coast, favours the increase of the water level and wave height and range along the coast.Keywords: cold fronts, Ekman transport, spring-tides, severe coastal erosion. RESUMO. O litoral de Salvador, no Estado da Bahia, possui um total de 20 praias, das quais 14 estão localizadas em região de mar aberto, no setor leste do Nordeste brasileiro, banhadas pelo oceano Atlântico, enquanto que as demais se encontram abrigadas na Baía de Todos os Santos. Dentre estas praias, muitas foram ou estão sendo acometidas por episódios de erosão costeira severa, que estão intrinsecamente relacionados à ação tanto de origem antrópica quanto natural. O presente estudo visou, através de análises e estatísticas de informações e dados como fotos, textos de jornais locais e cartas sinóticas e reanálises do National Centers for Environmental Prediction dos EUA, identificar os eventos de erosão severa relacionados à ocorrência de marés meteorológicas na orla de Salvador, no período de 1965 a 2006. Os resultados mostram que a maior parte dos eventos erosivos parece estar associada à ocorrência de marés meteorológicas, com grande potencial destrutivo. Este estudo permitiu constatar que a combinação: i) da ocorrência de marés de sizígia, com ii) a chegada de frentes frias e/ou o acoplamento de uma alta pressão a umcavado, nos baixos níveis da atmosfera, e iii) a predominância de ventos de S e SE, que através do transporte de Ekman, promovem empilhamento de água contra acosta, cria uma conjunção que favorece a sobre-elevação da altura e do alcance das ondas ao longo da costa.Palavras-chave: frentes frias, transporte de Ekman, maré de sizígia, erosão costeira severa.

This paper is concerned with the planning, implementation and some results of the Oceanographic Modeling and Observation Network (REMO) for Brazilian regional waters. Ocean forecasting has been an important scientific issue over the last decade due to studies related to climate change as well as applications related to short-range oceanic forecasts. It is a challenge to design an ocean forecasting system for a region with poor observational coverage of in situ data such as the South Atlantic Ocean. An integrated approach is proposed here in which the large-scale circulation in the Atlantic Ocean is modeled in a first step, and gradually downscaled into higher resolution regional models. This approach is able to resolve important processes such as the Brazil Current and associated meso-scale variability, continental shelf waves, local and remote wind forcing, and others. This article presents the overall strategy to develop the models using a network of Brazilian institutions and their related expertise along with international collaboration. This work has some similarity with goals of the international project Global Ocean Data Assimilation Experiment OceanView (GODAE OceanView), in which REMO takes part. Keywords : ocean models, ocean measurements, data assimilation. RESUMO . Este artigo apresenta o planejamento, implementacao e alguns resultados da Rede de Modelagem e Observacao Oceanografica, com acronimo REMO, para aguas territoriais brasileiras. A previsao de condicoes oceânicas tem sido um importante topico de pesquisa cientifica ao longo da ultima decada, devido a estudos relacionados com mudancas climaticas assim como interesse por previsoes sinoticas de curto prazo de variaveis tais como correntes marinhas e temperatura da agua. E um desafio realizar o projeto de um sistema de previsao para uma regiao oceânica com baixa disponibilidade de medicoes, como o Oceano Atlântico Sul. Uma proposta de desenvolvimento integrado e apresentada neste trabalho, onde um modelo de circulacao oceânica de todo Oceano Atlântico foi implementado como passo inicial, e gradualmente foram aninhados modelos regionais com maior resolucao espacial. Este artigo apresenta a estrategia de desenvolvimento destes modelos oceânicos utilizando o conhecimento cientifico disponibilizado por pesquisadores de uma rede de instituicoes brasileiras, com eventual colaboracao de pesquisadores internacionais. Esta iniciativa brasileira possui pontos comuns com um projeto de cooperacao cientifica internacional, denominado Global Ocean Data Assimilation Experiment OceanView (GODAE OceanView), da qual a REMO faz parte. Palavras-chave : oceanografia operacional, modelagem oceânica, sensoriamento remoto, medicoes oceanograficas, assimilacao de dados.

The results of two high-resolution ocean global circulation models – OGCMs (Hybrid Coordinate Ocean Model – HYCOM and Ocean Circulation andClimate Advanced Modeling Project – OCCAM) are analyzed with a focus on the Western Boundary Current (WBC) system of the South Atlantic Ocean. The volumetransports are calculated for different isopycnal ranges, which represent the most important water masses present in this region. The latitude of bifurcation of the zonalflows reaching the coast, which leads to the formation of southward or northward WBC flow at different depths (or isopycnal levels) is evaluated. For the Tropical Water,bifurcation of the South Equatorial Current occurs at 13◦-15◦S, giving rise to the Brazil Current, for the South Atlantic Central Water this process occurs at 22◦S.For the Antarctic Intermediate Water, bifurcation occurs near 28◦-30◦S, giving rise to a baroclinic unstable WBC at lower latitudes with a very strong vertical shearat mid-depths. Both models give similar results that are also consistent with previous observational studies. Observations of the South Atlantic WBC system havepreviously been sparse, consequently these two independent simulations which are based on realistic high-resolution OGCMs, add confidence to the values presentedin the literature regarding flow bifurcations at the Brazilian coast.Keywords: Southwestern Atlantic circulation, water mass, OCCAM, HYCOM. RESUMO. Resultados de dois modelos globais de alta resolução (HYCOM e OCCAM) são analisados focando o sistema de Corrente de Contorno Oeste do Oceano Atlântico Sul. Os transportes de volume são calculados para diferentes níveis isopicnais que representam as principais massas de água da região. É apresentada a avaliação da latitude de bifurcação do fluxo zonal que atinge a costa, permitindo a formação dos fluxos da Corrente de Contorno Oeste para o sul e para o norte emdiferentes níveis de profundidades (ou isopicnal). Para a Água Tropical, a bifurcação da Corrente Sul Equatorial ocorre entre 13◦-15◦S, originando a Corrente do Brasil, e para a Água Central do Atlântico Sul ocorre em 22◦S. A bifurcação daÁgua Intermediária Antártica ocorre próximo de 28◦-30◦S, dando um aumento na instabilidade baroclínica da Corrente de Contorno Oeste em baixas latitudes e com um forte cisalhamento vertical em profundidades intermediárias. Ambos os modelos apresentamresultados similares e consistentes com estudos observacionais prévios. Considerando que as observações do sistema de Corrente de Contorno Oeste do Atlântico Sul são escassas, essas duas simulações independentes com modelos globais de alta resolução adicionam confiança aos valores apresentados na literatura, relacionadosaos fluxos das bifurcações na costa do Brasil.Palavras-chave: circulação do Atlântico Sudoeste, massas de água, OCCAM, HYCOM.

The oceanic features in the eastern and southeastern Brazilian shelf/slope between 13◦-31◦S are investigated using ROMS (Regional Ocean Model System). The model was integrated for 9 years and it was forced with: i) 6-hourly synoptic atmospheric data from NCEP; ii) initial and boundary conditions from OCCAM (Ocean Climate Circulation Advanced Modelling) monthly mean climatology and iii) tidal forcing from TPXO 7.1 global data set. The model results were compared with observations, which consisted in thermodynamic MDL (Mixed Layer Depth) climatology, satellite data, measurements from tide gauges along the shelf and currents measurements values from literature. The simulated currents represented the BC (Brazil Current)-IWBC (Intermediate Western Boundary Current) System. The BC-IWBC system at 22◦S cross-shelf section represents our simulation capability of reproducing the western boundary currents, it showed poleward BC and a opposing IWBC. At this section, the BC velocity core is in 50 m with 0.41 m.s− 1 and the IWBC core around 800 m with 0.15 m.s− 1. Keywords : Western South Atlantic, ROMS, Western Boundary Currents. RESUMO . A circulacao oceânica na regiao da plataforma/talude do Brasil de 13◦-31◦S e investigada utilizando o modelo ROMS (Regional Ocean Model System). O modelo foi integrado por 9 anos e forcado com: i) dados atmosfericos sinotico a cada 6 horas do NCEP; ii) condicoes iniciais e laterais provenientes da climatologia mensal do modelo global OCCAM (Ocean Climate Circulation Advanced Modelling) e iii) forcamento de mare do modelo global TPXO 7.1. Os resultados do modelo foram comparados com observacoes, estas consistem em dados da profundidade da camada de mistura climatologica, dados de satelite, medicoes de maregrafos ao longo da plataforma e valores de medicoes de correntes disponiveis na literatura. As correntes simuladas representaram o sistema da CB (Corrente do Brasil)-CCI (Corrente de Contorno Intermediaria). O sistema CB-CCI na secao normal a costa em 22◦S representou a capacidade de simulacao das correntes de contorno oeste, mostrando a inversao de direcao das duas correntes. Nesta secao, o nucleo de velocidade da CB em 50 m apresentou valores de 0,41 m.s− 1 e o nucleo da CCI em 800 m apresentou velocidade de 0,15 m.s− 1. Palavras-chave: Sudoeste do Atlântico, ROMS, Correntes de Contorno Oeste.

Denomina-se Sistema Corrente do Brasil (CB) ao sistema de correntes de contorno oeste formados pela CB, fluindo para sul-sudoeste, e Corrente de Contorno Intermediária (CCI), fluindo para norte-nordeste, associado aos meandros e vórtices. O sistema bordeja a margem continental brasileira sudeste ao longo de 1200-1800 m. A investigação da dinâmica das ondas baroclínicas de vorticidade superpostas ao Sistema Corrente do Brasil é conduzida através exclusivamente de análise de dados hidrográficos de dois cruzeiros de meso-escala (verão e inverno de 1993) do projeto Circulação Oceânica da Região Oeste do Atlântico Sul - COROAS, a componente brasileira do World Ocean Circulation Experiment - WOCE. Estes cruzeiros foram realizados na porção central do Embaiamento de São Paulo (\'23,5 GRAUS\' - \'27 GRAUS\'S). Objetivando-se a aplicação do Método Dinâmico, estimativa quantitativa de um Nível de Referência (NR) é conduzida comparando-se duas metodologias diferentes e independentes. A primeira utiliza o fato de que a CB transporta Água Tropical (AT) e Água Central do Atlântico Sul (ACAS) e de que a CCI transporta dominantemente Água Intermediária Antártica (AIA). Aplica-se então um Critério Termodinâmico, no qual a interface que separa ACAS e AIA é estimada para os dois cruzeiros via aplicação dos Teoremas de Shtokman. A outra metodologia consiste na obtenção de padrões verticais de velocidade baroclínica absoluta a partir de simulações numéricas com a versão seccional do Princenton Ocean Model - POM inicializados com 14 campos termohalinos interpolados a partir dos dados - é o Critério Dinâmico. Os dois critérios apresentam resultado médio que difere apenas cerca de 7 dbar um do outro. Assim, adota-se valor de 480 dbar como NR para os cálculos geostróficos como nível isobárico que demarca a interface média entre CB e CCI. Mapas de função de corrente geostrófica são gerados através de mapeamento objetivo. Tais mapas apresentam evidências inequívocas de que os ciclones e anticiclones, observados nos experimentos de verão e inverno de 1993, são estruturas de vórtices associadas a meandros do Sistema CB. Este aparecem como estruturas vorticais postadas em lados diametralmente opostos ao eixo da CB: ciclones no lado costeiro, e anticiclones no lado oceânico. A variação vertical das estruturas dos meandros e a existência de uma única inversão de sentido permite comprovar e concluir que são ondas baroclínicas de primeiro modo, corroborando especulações presentes na literatura. A construção de um modelo quase-geostrófico de duas camadas para um oceano não-viscoso no plano \'beta\' e de fundo plano permite a realização de análise de vorticidade potencial. Tal análise permite concluir que o campo de vorticidade básico devido à CB suplanta o planetário e que estas ondas baroclínicas são ondas que devem sua existência ao cisalhamento vertical e horizontal da corrente. A variação frontal em vorticidade potencial baroclínica do Sistema CB é de \'1,7x10 POT.-5 s POT. -1\'. A dominãncia do termo da vorticidade de estiramento, que responde por 60% da variação de vorticidade na frente, permite estabelecer que as ondas capturadas na malha hidrográfica são ondas longas dentro da classe de meso-escala. O princípio de conservação de vorticidade potencial é invocado numa análise que envolve a superposição dos campos de vorticidade potencial e função de corrente para a primeira camada. Esta análise apresenta tanto evidências robustas de propagação das ondas baroclínicas quanto indícios de crescimento do meandro ciclônico, ou seja, de processo de instabilidade. Face aos achados das análises anteriores, teoria linear e método das perturbações são utilizados para obter uma relação de dispersão para as ondas baroclínicas da CB. Esta relação é dependente da velocidade da CB e do gradiente de vorticidade potencial através da corrente The Brazil Current System is formed by two western boundary currents that flow along the Southeast Brazil continental margin from surface to 1200-1800 m deep. These two currents are the southward-flowing Brazil Current (BC) and the northward-flowing Intermediate Western Boundary Current (IWBC). The investigation of the dynamics of the barociinic vorticity waves superimposed to the BC system is conducted in this work solely from hydrographic data anaiysis and manipulation from two oceanographic meso-scale surveys that were part of the COROAS Project, the Brazilian arm of the Worid Ocean Circulation Experiment. These two cruises sampled the central portion of the São Paulo Bight (23,5°- 27°S) in the summer and winter seasons of 1993. As it was intended to appiy the classical Dynamic Method to the data, a quantitative estimate of the reference levei (RL) is conducted through the comparison of two different and independent methodoiogies. The first uses the previous knowiedge that the BC transports Tropical Water and South Atlantic Central Water (SACW) as well as that the IWBC transports mainly Antarctic Intermediate Water (AAIW). This method, referred here as the Thermodynamic Criterion applies the Shtokman theorems to estimate the interface depth between SACW and AAIW. The second methodology, designated here as the Dynamic Criterion, consists of modeiing absolute baroclinic velocities for all 14 hydrographic transects using the sectional version of the Princeton Ocean Model. The results of the two methods differ oniy in 7 dbar and a RL of 480 dbar is adopted as to represent the average interface isobaric level between BC and IWBC in the following geostrophic calculations. Horizontal distributions of geostrophic stream function are generated using objective mapping. These distributions present unequivocal evidences of cyclonic and anticyclonic structures in both Summer and Winter 1993 cruises. These features are associated to meanders of the BC System. They are depicted in opposing sides of the current core. The cyclone is seen in the BC coastal side as the anticyclone is placed in its oceanic side. The vertical variation of these pattems with a single flow direction inversion confirms that these vortical features are part of a first baroclinic mode wave, which corroborates previous speculations found in the literature. In order to pursue a potential vorticity analysis, a data-derived two-layer quasi-geostrophic model is built assuming an invicid flat-bottomed ocean in the 3-plane. This analysis allowed to conclude that the basic vorticity field associated with both horizontal and vertical shear of the boundary currents are responsible for the baroclinic wave existence. The planetary vorticity gradient is one order of magnitude lower. The frontal variation in baroclinic potential vorticity is 1,7 x i0 s1. The dominance of the stretching vorticity, which accounts for 60% of the gradient variation, leads to classify these oscillatory motions as long meso-scale waves. The potential vorticity conservation principle is invoked on an analysis that consists of superimposing the first layer quasi-gesotrophic potential vorticity and geostrophic stream funtion maps. This analysis revealed that the baroclinic waves are propagating as well as evidences of meander growth, an indication of a possible geophysical instability mechanism, are seen. Given the findings of the previous analyses, linear theory and the perturbation method are used to derive a dispersion relation for the BC System first mode baroclinic waves. The wave frequency is function of the BC velocity as well as the potential vorticity cross-stream gradient.