Multi-scale dynamics on the Eastern Brazilian margin

Doutoramento em FísicaEste trabalho combina esforços de simulação numérica e de análise de dados para investigar a dinâmica em diversos compartimentos (oceano aberto, plataforma continental e zona costeira-estuarina) e, em multiplas escalas, na Margem Continental Leste Brasileira (MCLB). A circulação de largo e mesoescala espacial e a propagação da maré barotrópica são investigadas através de uma configuração aninhada do modelo numérico ROMS. O estudo da dinâmica regional da Baía de Camamu (CMB) baseia-se na análise de dados locais. A MCLB, localizada a SW do Atlântico Sul entre 8±S e 20±S, possui plataforma estreita, batimetria complexa, e baixa produtividade primária. A sua dinâmica é influenciada pela divergência da Corrente Sul Equatorial (CSE). As simulações refletem as conexões sazonais e espaciais entre a Corrente do Brasil e a Contra Corrente Norte do Brasil , em conexão com a dinâmica da CSE. As simulações revelam atividades vorticais nas proximidades da costa e interações com a dinâmica costeira, cujos padrões são descritos. A validação do modelo em mesoescala é baseada em cálculos de energia cinética turbulenta e em dados históricos de transporte. A CMB, localizada a 13±400S, abriga uma comunidade piscatória tradicional e extenso de manguezal. Situa-se porém sobre uma bacia sedimentar com grande reservas de óleo e gás, estando em tensão permanente de impacto ambiental. Neste trabalho sumarizamos as condições físicas regionais e investigamos sua dinâmica interna, focando sua variabilidade em amostragens realizadas sob condições de seca (Setembro de 2004) e de chuva (Julho de 2005). Finalmente, o modelo numérico ROMS é forçado com o sinal de maré, empregando-se uma configuração simples (com coeficientes de atrito de fundo constantes e condições hidrográficas homogéneas), com o intuito de avaliar sua resposta e investigar a natureza da propagação da maré barotrópica na MCLB, convergindo na CMB. A análise da resposta do modelo à maré basea-se em séries históricas do nível do mar para a MCLB e dados recentes da CMB.This work combines numerical and data analysis efforts to investigate the multiscale dynamics on the ocean, shelf and estuarine compartments of the Eastern Brazilian Margin (EBM). The large and mesoscale circulation and the barotropic tidal propagation are investigated with a nested configuration of the Regional Ocean Modeling System - ROMS. Regional Baía de Camamu (CMB) dynamics is investigated based on the analysis of an original field data covering dry and rainy conditions. The EBM is an oligotrophic and bathymetrically complex zone, on the NW South Atlantic (8±S to 20±S), whose dynamics is influenced by the divergence of the South Equatorial Current (SEC). The oceanic circulation reflects the seasonal and spatial relations between the southward Brazil Current and the northward North Brazil Undercurrent (NBUC), in connection to the SEC dynamics. While on the top layer (0-100 m) the circulation presents a pronounced spatial variability, on subsurface waters (100-500 m) the NBUC connects the EBM continuously. A first order description of eddies activities and its interaction with the near-shelf dynamics were considered. Eddy kinetic energy (EKE) calculated from AVISO sea level anomaly and transport estimates provides a validation of the mesoscale model results. CMB is a shallow bay system that sustains artisanal fisheries and extensive mangrove, but lies over a sedimentary basin with large oil and gas reserves, being under environmental pressure. We summarize the regional CMB physical setting and investigate the inner dynamics, its variability and major driving factors along Sept. (2004) and July (2005) field survey. Finally, tidal signals are added to the numerical model system with the objective of evaluating the model response, by using a simple configuration (that applies constant bottom stress and homogeneous hydrographic conditions), and to investigate the nature of the barotropic tidal propagation along different spatial scales over the EBM and towards CMB. The model tidal response is evaluated with historical short period tidal gauge data for the EBM and recent CMB pressure sensor data

Mean circulation, seasonal cycle and eddy interactions in the Eastern Brazilian Margin, a nested ROMS model

A nested configuration of the Regional Ocean Modeling System (ROMS) is used to study the seasonal circulation patterns and mesoscale activity of the Eastern Brazilian Margin (EBM). The EBM encompass an oligotrophic and bathymetrically complex zone in the NW South Atlantic from 8uS to 20 uS. Sea-level anomaly data are used to validate the model. Analysis of the mean circulation reveals that the EBM is dominated by seasonal and spatial dynamics of the southward Brazil Current (BC) and the northward North Brazil Undercurrent (NBUC), as well as their connection to the South Equatorial Current (SEC) dynamics. The EBM can be divided in three dynamic provinces, which are seasonally connected either by the permanent main flow or by mesoscale process. In the northern province, from 8uS to 13 uS, the NBUC is the major permanent feature and the BC is just a thin flow, confined to the top few meters. As it moves southward, the BC gets deeper and stronger. In the middle province, from 13uS to 16 uS, the dominance of the top 0–100-m circulation is seasonally alternated between the southward BC flow and the northward NBUC flow. In the southern province, from 16uS to 20 uS, the BC appears as a dominating surface feature. While on the top (0–100 m) the main current presents a pronounced seasonal and spatial variability, on subsurface waters (100–500 m) the NBUC connects the EBM continuously. Finally, analysis of the regional simulation reveals well-defined cyclonic and anticyclonic eddies. They detach from the main flow and translate along the domain throughout the year. The translation patterns are associated with the seasonal variability of the main EBM flow, with anticyclonic mesoscale features translating southward and mesoscale cyclonic features translating northward. On their pathway, these features may come very close to the margin, interacting with the near-shelf flow.publishe

Plano de análise estatística para o estudo Balanced Solution versus Saline in Intensive Care Study (BaSICS)

OBJECTIVE: To report the statistical analysis plan (first version) for the Balanced Solutions versus Saline in Intensive Care Study (BaSICS). METHODS: BaSICS is a multicenter factorial randomized controlled trial that will assess the effects of Plasma-Lyte 148 versus 0.9% saline as the fluid of choice in critically ill patients, as well as the effects of a slow (333mL/h) versus rapid (999mL/h) infusion speed during fluid challenges, on important patient outcomes. The fluid type will be blinded for investigators, patients and the analyses. No blinding will be possible for the infusion speed for the investigators, but all analyses will be kept blinded during the analysis procedure. RESULTS: BaSICS will have 90-day mortality as its primary endpoint, which will be tested using mixed-effects Cox proportional hazard models, considering sites as a random variable (frailty models) adjusted for age, organ dysfunction and admission type. Important secondary endpoints include renal replacement therapy up to 90 days, acute renal failure, organ dysfunction at days 3 and 7, and mechanical ventilation-free days within 28 days. CONCLUSION: This manuscript provides details on the first version of the statistical analysis plan for the BaSICS trial and will guide the study's analysis when follow-up is finished