César Barbedo Rocha.

Estudos recentes mostram que é cada vez mais provável a ocorrência de mudanças abruptas no clima ainda no presente século. Um desses trabalhos, baseado no balanço de água doce no Oceano Atlântico, sugere um indicador capaz de antever em 25 anos mudanças abruptas do clima. Nesse estudo, modelo climático e produtos de reanálise mostram que o colapso do sistema de correntes oceânicas que ajuda a regular o clima poderia estar ocorrendo com velocidade tal que a adaptação seria simplesmente impossível. Entretanto, dada a insuficiência de informações fornecidas pelas atuais reanálises, somente observações continuadas poderiam fornecer uma estimativa mais confiável da distância do estado atual ao próximo ponto de mudança abrupta. O referido estudo sugere também que, para estimar quão próximo estamos do colapso, observações ao longo da latitude 34S no Atlântico Sul são de extrema importância e cruciais. Coincidentemente, desde 2008 um grande programa internacional de observações tem sido implementado no Atlântico Sul, com destacada liderança e contribuição do Brasil. Esse programa inclui uma série de plataformas observacionais instaladas ao longo da latitude 34.5S e no Canal de Vema, este último uma estreita passagem na topografia de fundo, conectando as regiões abissais das Bacias da Argentina e do Brasil. No presente projeto, propõe-se uma investigação minuciosa das condições médias e da variabilidade das águas profundas na região, e dos transportes de calor e água doce pela circulação oceânica no Atlântico Sul. Ênfase será dada ao estudo da variação temporal do transporte de água doce pela circulação de revolvimento meridional em 34.5S, o indicador de possíveis instabilidades e pontos de mudanças abruptas do clima. Serão analisados dados observacionais já disponíveis ou sendo coletados no Atlântico Sul. Adicionalmente, simulações numéricas e modelos de aprendizagem de máquina serão utilizados na estimativa das correntes e do transporte meridional de calor e água doce.

O Brasil é amplamente conhecido como um dos países mais biodiversos do planeta. Entretanto, boa parte desse foco está sobre os ecossistemas terrestres, embora o país detenha um território marinho de 3,6 milhões de km2. No Brasil, o desconhecimento sobre o ecossistema marinho fica ainda mais evidente ao se considerar que a educação sobre o oceano em escolas e a pesquisa oceânica em universidades fora da zona costeira é bastante limitada, e muitas vezes desestimulada, pela falta de compreensão sobre a influência que exercemos sobre o mar e o mar sobre nós. Com foco na conectividade, baseamos nossa proposta na criação de dois produtos, sendo (i) um relatório multidisciplinar visando responder a três perguntas fundamentais: (1) Quais as principais ameaças à biodiversidade marinha no Brasil hoje? (2) De que forma uma melhor compreensão sobre a influência do oceano na vida, saúde e bem estar do brasileiro pode contribuir para a preservação da biodiversidade marinha no Brasil? (3) De quais formas o oceano impacta e é impactado pela vida do brasileiro habitante do interior do país? Além dos problemas, o documento irá, também, apontar soluções. O segundo produto será (ii) uma ilustração baseada em ciência e dados na qual iremos narrar a trajetória de uma tampa de garrafa PET jogada em um rio no interior do Nordeste até sua chegada ao mar, indicando diferentes possibilidades de impactos ao longo da trajetória e, também, em seu destino, onde o efeito cumulativo de ações humanas resultam em múltiplas ameaças. A ilustração será apresentada em uma reportagem interativa a ser publicada pela Ambiental Media.

The ocean plays a central role in Earths changing climate. It has absorbed about 30 of carbon dioxide from burning fossil fuels in the industrial era and taken up, in the form of heat, about 90 of the radiation imbalance caused by the excess greenhouse gases, carbon dioxide included, that remained in the atmosphere. Global warming and its consequences thus depend crucially on the rates at which heat and carbon dioxide are absorbed at the air-sea interface, sequestered into the ocean interior, and redistributed across the global ocean. This in turn depends on eddying processes that stir and mix and transport heat, carbon and other tracers, whose physics are by and large poorly understood and whose models are largely divorced from robust in-situ measurements.This project focuses on a class of relatively small eddying processes called submesoscales fronts, instabilities and eddies with horizontal scales of several hundreds of meters to about 20 km. We will test the hypothesis that submesoscale phenomena in the upper ocean play an important role in large-scale ocean circulation and climate. To that end, we will analyze unprecedented observations of submesoscale flows that we recently collected as part of the Submesoscale Ocean Dynamics Ex- periment (SMODE) and of sea-surface height and derived geostrophic velocities from the recently launched Surface Water Ocean Topography (SWOT) satellite mission. From SMODE velocity and water density measurements collected with an array of robotic sailboats traveling in subme- soscale formation, we will calculate kinematic quantities such as vertical vorticity and horizontal divergence and estimate the vertical velocity across different submesoscale flows (fronts, instabili- ties, etc). More important, we will use these data and analysis to inform the development and test the predictions of a hierarchy of theoretical and numerical models that we will develop with the goal of characterizing the lateral and vertical transport by submesoscale flows. These include ideal- ized models with simple geometry and reduced equations (surface quasi-geostrophic model, stacked- Eady quasi-geostrophic model, Young-and-BenJellou model), models with simple geometry but full Boussinesq hydrostatic equations, and realistic submesoscale-resolving models in the Southwestern Atlantic. From the SWOT data, we will characterize the statistics and structure of submesoscale geostrophic velocities. SWOT geostrophic velocities will also be used to advect tracers and particles to estimate the eddy diffusivity due to balanced submesoscale flows.By the end of this project, we expect to produce a nuanced, quantitative characterization and phys- ical understanding of submesoscale eddy transport, based on solid theoretical ground and constrained by in-situ observations. Such an understanding is crucial to developing physically meaningful pa- rameterizations of submesoscale eddy transport in climate models and therefore can pave the way for more accurate long-term climate forecasts. We also expect to produce a global estimate of the contri- bution of submesoscale phenomena to the total eddy transport in the global ocean. The project will support the Principal Investigatora young scientist who was recently recruited back to Brazil after 9.5 years in the United Statesto establish his research group at Universidade de Sa #771;o Paulo, starting a new research line in the country while maintaining his broad array of international collaborations. The project will fund two graduate and four undergraduate students, who will be trained in ocean and climate physics through cutting-edge research, learning skills highly valued in academic research and transferable to many careers in industry.

The global overturning circulation (GOC) is a set of large-scale ocean currents that transport copi- ous amounts of heat. Changes in the GOC, particularly in its Atlantic branch, the AMOC (Atlantic Meridional Overturning circulation), are intimately linked to variability in Earths climate. Research in the past 20 years has established that the MOC upper cell is closed by wind-driven upwelling of deep waters in the Southern Ocean. Much less is known about the mechanisms responsible for the AMOC bottom cell. This is a proposal to test the hypothesis that the variability of the AMOC bottom cell is set by fluctuations in vertical mixing due to small-scale turbulence caused by breaking internal waves in the abyssal ocean. We will use high-quality density and horizontal velocity profiles collected over the past 13 years to infer small-scale eddy kinetic dissipation rates and diapycnal diffusivities via finescale parameterizations. We will also use a set of idealized numerical simulations of stratified shear turbulence to assess the underlying assumptions of such parameterizations and to describe and quantify the processes linking internal waves to instabilities to turbulence and mixing. The estimated turbulence and mixing will be used to investigate whether mixing can explain the observed annual to decadal variability in the AMOC bottom cell transport. Our results will illuminate the dynamics of ocean processes that are critical to understanding the oceans role in Earths climate and could help improve numerical models for the prediction of climate variability and change.

A defasagem em matemática de vários alunos do Bacharelado em Oceanografia é um relevante gargalo para seu desempenho e aproveitamento. Visando aliviar esse gargalo, identificado na reformualação do Projeto Político Pedagógico do Bacharelado em Oceanogra, o presente proojeto PUB-Ensino visa desenvolver material didático para em matemática voltado a discentes do Bacharelado em Oceanografia, que servirá para o nivelamento dos ingressantes no Bacharelado em Oceanografia bem como de material de apoio para a disciplina IOF027 Oceanografia Física I (a primeira disciplina do eixo de oceanografia física). Espara-se que o material desenvolvido, com foco em aplicações relevantes para Oceanografia, melhore o aprendizagem e a retenção de conhecimento em cálculo diferencial e integral. contribuindo para uma melhora no aproveitamento do curso e, possivelmente, para a diminuição da evasão. A(o) bolsista auxiliará o docente na elaboração de testes de conhecimento, notas de aula, listas de exercícios de pré-calculo e cálculo diferencial e integral. Como parte do projeto, a(o) bolsista desenvolverá diversas habilidades e compotências transferíveis, como elaboração e solução de problemas, redação e edição de documentos matemáticos em LaTeX e edição de vídeos.

Estudos sobre o registro geológico da ação da Água Intermediária Antártica no Atlântico Sudoeste são bastante escassos, apesar de seu papel fundamental na cisculação meridional. Essa massa de água, transportada pelo Giro Subtropical, sofre uma bifurcação quando atinge a margem oeste do Atlântico Sul, formando a Bifurcação de Santos. Neste projeto propomos o estudo da Bifurcação de Santos em diversas escalas temporais, numa abordagem interdisciplinary, que envolve sua variabilidade espacial ao longo de dezenas a minhares de anos. Ao estudar a variabilidade da Bifurcação, os autores entendem ser possível o reconhecimento da própria variabilidade da Água Intermediária Antártica. A abordagem metodológica envolve desde medições de velocidades de correntes até analyses paleoceanográficas, envolvendo o estudo de testemunhos e modelagem em larga escala. O projeto envolve pesquisadores de três institutos do Estado de São Paulo, um do Paraná e um dos Estados Unidos.

This project aims to advance the science and technology of data assimilation of surface wind, sea wave, and surface ocean current in the 3 Dimensional- Real Time Mesoscale Analysis (3D-RTMA). Analysis of marine variables require an effective exploitation of observational information and the integration of models that capture key processes and air-sea interactions occurring over a wide range of spatial and time scales. The proposed system aims to improve the blending of global and local-scale weather and oceanographic variability in the RTMA by expanding the JEDI protocols to include marine observations, and by using sound scientific principles of mesoscale modeling. The products of the operational (2D) RTMA are used for guidance, monitoring, and forecast verification in NWS forecast offices. This project will extend this capability to support offices in charge of providing marine and ocean analysis products by establishing skillful estimates of the state of waters at the margins of the continental U.S., and to facilitate a community of practice for observing data integration and coastal model evaluation. Four key enhancements are pursued: physical consistency of the three-way interaction wind-waves-currents, reduced bias of the background fields, higher fidelity of fields, and improved analysis uncertainty estimation. To achieve the proposed enhancements the following objectives are pursued: (1) increase the robustness of the data quality control system for marine and ocean variables–especially the High Frequency radar and satellite altimetry data, (2) implement the IODA libraries for preparation of forward operators for each of the new observations to be included, (3) implement an appropriate configuration of the regional MOM6 ocean model to provide surface current’s first guess fields, (4) implement a field-alignment processing scheme for positional and amplitude error reduction in the background fields, (5) develop and evaluate configurations of the background error covariance across the three fields, and (6) design, develop, and test a hybrid EnVAR data assimilation scheme of wind-wave assimilation constrained to current conditions. These proposed advancements of the data assimilation scheme will leverage on the ongoing NOAA developments of the 3D-RTMA, the UFS, and the JCSDA’s developments of JEDI project. In turn, this project will lead developments towards future coupled wind-wave-current data assimilation schemes.

The South Atlantic is unique in that it transports heat equatorward instead of poleward, and recent studies suggest that the South Atlantic meridional overturning circulation (MOC) undergoes strong short-term variability, likely due to mesoscale eddies. Nevertheless, the Brazilian continental margin, upstream of the Brazil-Malvinas Confluence, lacks an in-depth characterization of mesoscale eddies. This project will develop a detailed characterization of the structure and variability of eddies in this region using a synergistic observational approach. The project will inform efforts to model carbon sequestration and redistribution, which requires an accurate representation of mesoscale eddies by providing an observational benchmark. Data from altimetric products (along-track and mapped absolute dynamic topography and sea-level anomalies as well as eddy-tracking trajectories), Argo floats (profiles and trajectories), and high-resolution XBT/CTD transects will be used. For the Brazilian continental margin region between about 20 to 35 degrees S, the project aims to characterize the synoptic horizontal and vertical structure of eddies, build eddy composites and estimate their anomalous heat and salt/freshwater contents. These approaches will be utilized to differentiate between local and remote eddies in the Brazil Current region, test the hypothesis that remote eddies contribute significantly to the mesoscale variability in the Brazil Current region, and produce a detailed look into the mesoscale variability of the Brazilian continental margin. Specifically, the project will (a) characterize the statistics of eddy characteristics and their seasonal and interannual variability, (b) study in detail representative individual eddies, (c) build two-dimensional and three-dimensional eddy composites and (d) quantify the anomalous heat and salt/freshwater content of eddies.

A major difficulty in simulating Earth's climate system is that there are interactions across scales, so that the large time and space scales can be sensitive to processes on small scales. As the computational resolution of global ocean models has improved, scientists have begun to suspect that kilometer-scale eddies and fronts, called "submesoscale" variability, have a net effect on ocean-atmosphere heat exchange that is larger than the heating from the greenhouse effect (Su et al. 2018). State-of-the-art computer models agree in predicting that these eddies have important long-term effects on the upper-ocean, but their predictions are sensitive to relatively small details in model physics and implementation. The resolution and detail of these simulations has surpassed our ability to "ground truth" them with spaceborne or in situ sensors. There is thus a pressing need for a comprehensive benchmark data set on these submesoscale motions to address this important source of uncertainty in simulating the global ocean.

This mission will test the hypothesis that submesoscale ocean dynamics make important contributions to vertical exchange of climate and biological variables in the upper ocean. This will require coordinated application of newly-developed in situ and remote sensing techniques, and it will provide an unprecedented view of the physics of submesoscale eddies and fronts and their effects on vertical transport in the upper ocean. The Sub-Mesoscale Ocean Dynamics Experiment (S-MODE) will use measurements from a novel combination of platforms and instruments, along with data analysis and modeling, to test the hypothesis.

The ocean energy budget is not well understood and there is uncertainty in the content of and fluxes between ocean energy reservoirs. Internal waves, which result from wind, tides and topographic interactions, are present throughout the ocean and contain about 10% of the ocean energy budget while the remaining 90% is associated with mesoscale eddies. In order to reach steady-state, the same amount of energy entering the system must leave the system; however, the method of removal is not clear. This group of researchers has recently obtained results that suggest a transfer of energy from the mesoscale flow to near-inertial waves. This loss of energy is also known as the stimulated loss of balance (SLOB), which influences mesoscale flow. This project seeks to quantify the impact of ocean internal waves on mesoscale flow as well as determine if internal tides also act as a source of energy transfer. The researchers plan to utilize theory and numerical simulations to investigate the role of internal waves in the mesoscale energy budget. The knowledge gained from this proposal will enhance understanding of internal waves, which can be used to advance climate models. A better understanding of internal tides will likely lead to more accurate interpretations of satellite altimeter data as well. Two postdoctoral research assistants will benefit from state-of-the-art physical oceanography and applied mathematics training through this project. This project supports an international collaboration between Scripps Institute of Oceanography and the University of Edinburgh. The resulting models and model output will be made available to other researchers for teaching and learning purposes.

Recent results produced by this group of researchers show that the advection and refraction of near-inertial waves by mesoscale flow is necessarily accompanied by a transfer of energy from the mesoscale flow to the inertial waves. Theoretical and numerical analyses will be used to develop a model that couples internal wave dynamics with that of balanced mesoscale flow to understand energy transfers from the mesoscale reservoir to internal waves via SLOB. The specific objectives of this project are to: assess and develop the hypothesis that SLOB plays a major role in the mesoscale energy budget, and to investigate SLOB by components of the internal wave spectrum, particularly the internal tide. The proposed methodology will also aid in the development and assessment of techniques with broad applicability to multi-scale problems involving the scattering and transformation of waves by turbulent flows. As a result of this project, a quantitative understanding of the role played by SLOB in the ocean energy budget will be obtained.

To support the interpretation of satellite altimeter data and the planning of the Surface Water Ocean Topography (SWOT) mission, I propose a computational, observational, and theoretical effort to characterize the mesoscale to submesoscale dynamics of unsteady currents in upper ocean, with particular focus on the energy transfers across different scales, the partition of KE between geostrophic and ageostrophic flows, and the consequences of energetic submesoscale flows. As part of this program I will:
I characterize the geographic and seasonal variability of the upper ocean wavenumber spectra of kinetic energy and SSH variance, and their relationship;
II investigate the wavenumber spectra of fully-developed geostrophic turbulence driven by different flavors of baroclinic instability in the ocean; and
III assess the implications of the observed spectra for the interpretation of high-resolution altimeter data and their application to quantify ocean mixing.
In the NASA spirit, this project breaks artificial barriers that separate analysis of observa-
tions, high-performance computing, and theory. The proposed study builds on the research that I carried out during my first two years at Scripps Institution of Oceanography (Rocha et al., 2015a, 2016). The altimeter and model output analysis applied to the Drake Passage region by Rocha et al. (2016) will be extended to several select regions of the ocean. The spectral code that I have been developing with colleagues (Rocha et al., 2015b) will be extended to ac- count simultaneously for surface and interior quasigeostrophic dynamics, e.g., using the Galerkin approximation developed by Rocha et al. (2015a), and applied to data-based basic states to elu- cidate the physics behind the observed spectra. The consequences of the observed KE spectra to altimeter-based studies of ocean mixing will also be investigated.
This better understanding of the global upper ocean wavenumber spectra will support the planning of the SWOT mission, and provide a modern framework for interpretation and application of SWOT measurements and of NASA's extraordinary heritage of altimeter data. While the development of parameterizations is not a main topic of this proposal, the results of this project will support the broader goal of incorporating the physics of submesoscale flows into coarse-resolution climate models.

The wind over the ocean generates oscillations called near-inertial waves (NIW). The subsequent downwards and equator-ward propagation of these NIWs is a main path for mechanical energy from the wind to travel from the surface into the deep ocean. Via wave-wave interactions and scattering, NIWs and internal tides energize the remainder of the internal wave band. Moreover, NIWs control the local stability of the water column that is relevant for breaking and mixing throughout the ocean's depths. A main dynamical reason for the dominance of NIWs which contain about half of the kinetic energy in the ocean is that the inertial frequency is the lowest available to the internal wave band, and the quasi-horizontal oscillatory motion of NIWs offers little impedance to surface wind stress and stratification. Because of their volatile response to atmospheric (wind) forcing, NIWs cannot be described as part of a "universal" wave spectrum of internal gravity waves and different approaches and theories are needed. 

A theoretical and computational effort will be directed at three problems related to the generation and propagation of ocean near-inertial waves (NIWs): (a) the interaction of NIWs with geostrophically balanced eddies, particularly the exchange of energy between eddies and NIWs; (b) the windy generation of NIWs, the role of the beta-effect versus eddy vorticity gradients in accelerating vertical radiation, and the reflection of NIWs from seafloor topography with bottom slopes that are comparable to, or larger than, the wave slope; (c) the interaction of surface gravity waves with NIWs and the partitioning of wind stress between the two modes during the generation process. The processes above control the rate at which the wind works on the ocean internal wave field, the damping of mixed-layer near-inertial oscillations and the downward and equatorward radiation of NIWs. These mechanisms act on time scales ranging from a few seconds (gravity wave frequencies) to weeks (surface-intensified geostrophic eddies). Theoretical developments involve multi-scale analysis, stochastic modeling and averaging. Although parameterization is not an immediate goal of this project, the process-oriented work proposed here is essential to the incorporation of internal-wave physics into comprehensive circulation models.

Neste projeto, propomos a avaliação de um método para a reconstrução da dinâmica de mesoescala da Corrente do Brasil (CB) a partir de imagens de temperatura da superfície do mar (TSM). Para tal, utilizaremos um modelo baseado na teoria quase-geostrófica superficial (QGS) (Held et al., 1995). Nossa hipótese é que a CB possui uma estrutura de vorticidade potencial confinada à superfície/subsuperfície (0-200 m), sendo portanto possível aplicar um modelo QGS em seu domínio. Propomos avaliar o método através de sua aplicação em três localidades (22, 25 e 28$oS), nas quais a CB possui caracteríticas dinâmicas distintas. A verificação/validação será feita através da comparação com séries temporais de fundeios correntográficos. A aplicação deste método é uma forma dinamicamente consistente de estimar os campos de velocidade superficial e subsuperficial. Dessa forma, será possível utilizá-lo em estudos para o melhor entendimento da dinâmica da CB, e como uma forma dinamicamente fundamentada de assimilação de dados de TSM em modelos numéricos para previsão oceânica, fundamentais para as atividades de exploração de petróleo e gás na região.

Embora seja comum a existência de recirculações nos giros dos oceanos mundiais, muito pouco se conhece a respeito do processo de recirculação na porção interna do Giro Subtropical do Atlântico Sul, pois há carência de conjunto de dados sinóticos que capturem essa feição. Como um passo inicial para entendimento da dinâmica da recirculação, propomos, no presente trabalho, representar o Sistema Corrente do Brasil-Célula de Recirculação (CBCR) por um simples modelo paramétrico baseado em sua estrutura de velocidade. O objetivo é descrever a estrutura tridimensional do Sistema CBCR. A partir do modelo paramétrico para a velocidade, propomos calcular o campo de função de corrente. Para reconstruir o campo de densidade potencial, propomos um modelo inverso baseado na assinatura quase-geostrófica do Sistema CBCR no campo de massa. Para reconstituir os campos de temperatura (T) e salinidade (S), propomos utilizar um sistema de duas equações formado por uma forma linear da \textit{Equação de Estado da Água do Mar} [$\rho = \rho(S,T,0)$] e um polinômio do segundo grau ajustado para a relação T-S [$S = S(T)$]. Por fim, propomos interpolar os campos de T e S junto com uma climatologia, introduzindo a energia em escala sinótica à circulação média climatológica. Esperamos obter funções simples para representar a estrutura de velocidade. Esperamos também obter uma boa representação dos campos de densidade, temperatura e salinidade, que nos permitam descrever a estrutura tridimensional da porção interna do giro.