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Coastal and shelf circulation in the vicinity of Camamu Bay (14 degrees S), Eastern Brazilian Shelf

AMORIM, F. N.; CIRANO, M.; SOARES, I. D.; LENTINI, C. A. D.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.32%
The Camamu Bay (CMB) is located on the narrowest shelf along the South American coastline and close to the formation of two major Western Boundary Currents (WBC), the Brazil/North Brazil Current (BC/NBC). These WBC flow close to the shelf break/slope region and are expected to interact with the shelf currents due to the narrowness of the shelf. The shelf circulation is investigated in terms of current variability based on an original data set covering the 2002-2003 austral summer and the 2003 austral autumn. The Results show that the currents at the shelf are mainly wind driven, experiencing a complete reversal between seasons due to a similar change in the wind field. Currents at the inner-shelf have a polarized nature, with the alongshore velocity mostly driven by forcings at the sub-inertial frequency band and the cross-shore velocity mainly supra-inertially forced, with the tidal currents playing an important role at this direction. The contribution of the forcing mechanisms at the mid-shelf changes between seasons. During the summer, forcings in the two frequency bands are important to drive the currents with a similar contribution of the tidal currents. On the other hand, during the autumn season, the alongshore velocity is mostly driven by sub-inertial forcings and tidally driven currents still remain important in both directions. Moreover...

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

Lopes, Alexandre Bernardino; Harari, Joseph
Fonte: INST OCEANOGRAFICO, UNIV SAO PAULO; SAO PAULO Publicador: INST OCEANOGRAFICO, UNIV SAO PAULO; SAO PAULO
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.12%
The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

The influence of large-scale circulation, transient and local processes on the seasonal circulation of the Eastern Brazilian Shelf, 13 degrees S

Amorim, Fabiola Negreiros de; Cirano, M.; Soares, I. D.; Campos, Edmo Jose Dias; Middleton, J. F.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.29%
The circulation at the Eastern Brazilian Shelf (EBS), near 13 degrees 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 mesa/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...

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

Lopes, Alexandre Bernardino; Harari, Joseph
Fonte: Universidade de São Paulo, Instituto Oceanográfico Publicador: Universidade de São Paulo, Instituto Oceanográfico
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.12%
The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

Ondas instáveis no sistema de correntes de contorno oeste ao largo de Abrolhos; Unstable Wares in the western boundary currents system off Abrolhos

Soares, Saulo Muller
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/06/2007 PT
Relevância na Pesquisa
66.35%
O sistema de correntes de contorno oeste que flui ao largo da costa leste brasileira entre 15°S e 22°S, é composto pela Corrente do Brasil (CB) fluindo para sul, a Sub-Corrente Norte do Brasil (SNB) fluindo para norte e a Corrente de Contorno Oeste Profunda (CCP) também fluindo para sul. Vigorosos meandros e vórtices são observados à jusante dos Bancos de Abrolhos (BA) e Royal Charlotte (BRC) e da Cadeia Vitória-Trindade. O objetivo central desta dissertação é o estudo da estabilidade deste sistema de correntes, aqui denomidado Sistema CB-SNB-CCP, utilizando o modelo oceânico da Universidade de Princeton (POM) em um cenário idealizado. Buscamos responder o quão instável é este sistema e quais seriam as características das ondas instáveis geradas a fim de contribuir para o conhecimento acerca da rica dinâmica de meso-escala observada nesta região. Objetivamos também, elucidar o papel dos BA e BRC nesta dinâmica. Embasados na alta baroclinicidade do sistema de correntes de contorno ao largo do sudeste brasileiro, optamos por representar o escoamento CB-SNB-CCP através de um modelo paramétrico do campo de massa, calibrado com os dados hidrográficos oriundos dos Cruzeiros Abrolhos [Silveira et al., 2006]. Mantendo o caráter idealizado do estudo...

Variabilidade subinercial das correntes na plataforma continental ao largo de Cabo Frio (RJ): observações; Subtidal variability of the currents on the continental shelf off Cabo Frio (RJ): observations

Santos, Luis Felipe Silva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/03/2010 PT
Relevância na Pesquisa
36.1%
Este trabalho foi desenvolvido dentro do contexto da hidrodinâmica da plataforma continental, com o objetivo de estudar a variabilidade subinercial das correntes no extremo norte na Plataforma Continental Sudeste brasileira. A região de estudo está localizada nas proximidades de Cabo Frio (RJ) e Arraial do Cabo (RJ) (aproximadamente 23º S / 42º W). Apesar de ser uma região bastante conhecida e estudada, em função do fenômeno da ressurgência costeira que ocorre em suas proximidades, pouco se conhece sobre a circulação subinercial nessa localidade. Devido à importância das correntes subinerciais, por serem responsáveis pelo transporte de substâncias dissolvidas ou em suspensão nas águas, tais como sedimentos, nutrientes e poluição, este trabalho tenta contribuir com um maior conhecimento desses campos de corrente, a partir da análise, no domínio do tempo e da frequência, de séries temporais de intensidade e direção das correntes e do vento local. Foram utilizados dados coletados no Projeto DEPROAS (Dinâmica do Ecossistema de Plataforma da Região Oeste do Atlântico Sul) a partir de correntógrafos e ADCP fundeados, numa radial em frente a Cabo Frio, sobre as isóbatas de 50, 100 e 200 m, bem como de uma bóia e de uma estação meteorológicas. Trabalhamos com as séries temporais do inverno de 2001 e do inverno e verão de 2003. A partir desse estudo foi possível verificar que a variabilidade subinercial domina o fluxo das correntes na região...

Dinâmica quase-geostrófica do sistema corrente do Brasil no embaiamento de São Paulo (23,5º - 27º S); Quasi-geostrophic dynamics of Brazil current system in The São Paulo Bight (23.5º - 27ºS)

Godoi, Sueli Susana de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 02/09/2005 PT
Relevância na Pesquisa
36.24%
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...

A Dinâmica Sazonal da Plataforma Continental Leste Brasileira entre 10ºS e 16ºS; The Seasonal Dynamics of the Eastern Brazilian Shelf between 10ºS e 16ºS.

Amorim, Fabiola Negreiros de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 10/10/2011 PT
Relevância na Pesquisa
46.25%
A circulação sazonal da Plataforma Continental Leste Brasileira (PCLB) entre 10oS e 16oS é investigada com base em um inédito conjunto de dados in situ e em modelagem hidrodinâmica. Os dados observados possibilitaram a compreensão da dinâmica da circulação em partes específicas da região de estudo e a sua interação com os diversos mecanismos forçantes, ilustrando a forte influência da circulação atmosférica e oceânica de meso/larga escalas, de processos transientes e da topografia local, na circulação regional, apresentando cenários distintos entre as estações do ano. Os resultados da modelagem hidrodinâmica não só complementaram os estudos observacionais, como também permitiram uma maior compreensão da variabilidade sazonal e espaço-temporal da circulação na PCLB, assim como a sua interação com os diversos mecanismos forçantes, para uma região mais ampla (10oS-16oS). A PCLB é fortemente afetada pela sazonalidade de larga escala do regime dos ventos alísios e da latitude da Zona de Convergência Intertropical (ZCIT). Seguindo esta dinâmica, durante as estações de primavera/verão, as correntes na Plataforma Continental (PC) ao sul de 12oS ficam sujeitas a ventos preferenciais de E-NE e, no oceano...

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

Lopes,Alexandre Bernardino; Harari,Joseph
Fonte: Universidade de São Paulo, Instituto Oceanográfico Publicador: Universidade de São Paulo, Instituto Oceanográfico
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2012 EN
Relevância na Pesquisa
46.12%
The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.

Variation in the strength of continental boundary currents determines continent-wide connectivity in kelp

Coleman, M.; Roughan, M.; Macdonald, H.; Connell, S.; Gillanders, B.; Kelaher, B.; Steinberg, P.
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
46.45%
1. Determining the extent to which coastal oceanographic processes facilitate connectivity of marine organisms underpins our understanding of the ecology and evolution of marine communities. Continental boundary currents are a dominant physical influence on marine connectivity, but determining their effect has proved elusive because of difficulties in achieving replication of currents within the distribution of a single species. 2. Australia provides an unparalleled opportunity to address such questions because it has three replicate boundary currents within narrow latitudinal ranges that share continentally distributed species. We tested whether the strength of continental boundary currents influences coastal connectivity of a dominant foundation species (the kelp Ecklonia radiata). 3. Variation in the strength of different boundary currents produced entirely different patterns of connectivity in kelp with high connectivity in strong currents and low connectivity in weak currents. Spatial patterns of genetic structuring were also correlated with the nature and strength of currents. 4. SYNTHESIS. This result has global implications; continental boundary currents are key drivers of marine connectivity and give predictive ability with which to understand variable ecologies of temperate coastlines world-wide.; Melinda A. Coleman...

Temperate shelf water dispersal by Australian boundary currents: implications for population connectivity

Coleman, M.; Feng, M.; Roughan, M.; Cetina-Heredia, P.; Connell, S.
Fonte: Duke University Press Publicador: Duke University Press
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
46.34%
Boundary currents have been recognized as potential drivers of spatial heterogeneity in the ocean because of their role in physical transport and influence on large-scale coastal processes. In this study, we used particle tracking methods in a data-assimilating eddy-resolving ocean circulation model to determine the effect of multiple boundary currents on connectivity around temperate Australia during the austral winter. Results demonstrated that oceanographic connectivity was asymmetric around Australia, having greater eastward trajectories due to more favorable ocean boundary currents during this season. We validated connectivity patterns with genetic data from an ecologically important species, the kelp, Ecklonia radiata, which has greater genetic similarity between the west and south coasts of Australia, compared with the east coast, likely due to predominantly eastward propagule dispersal. Boundary current circulation was a coarse predictor of kelp genetic connectivity on multigeneration time scales, and the nature of these relationships varied among the three boundary current systems according to mean current strength.; Melinda A. Coleman, Ming Feng, Moninya Roughan, Paulina Cetina-Heredia and Sean D. Connell

Dynamics of eastern boundary currents and their effects on sound speed structure

Guthrie, Vanessa M.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado
Relevância na Pesquisa
36.05%
Identifying the influence of eastern boundary current (EBC) dynamical processes on sound speed structure can provide better ocean models for acoustic predictions in littoral regions. This study will explore the effects of currents, wind and eddies on the sound speed structure of two different EBC models, the North Canary Current System (NCCS) and the Leeuwin Current System (LCS). These systems represent classical features of EBCs as well as regional anomalies. This study seeks to introduce sound speed analysis to the sigma coordinate primitive equation models and determine which regions of EBCs experience the largest changes in sound speed and most intense gradients. Results of model runs show that the dynamics of EBCs lead to large changes in sound speed and distort the vertical sound speed profile. The greatest change in sound speed in either region is caused by upwelling in the NCCS. Surface and associated subsurface eddies in the LCS are the largest scale feature in the study. The undercurrent of the NCCS and Meddies present the most intense (horizontal and vertical) gradients of sound speed change.

Evolution of diurnal surface winds and surface currents for Monterey Bay

Foster, Michael D.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: 100 p.; 28 cm.
EN_US
Relevância na Pesquisa
36.1%
Approved for public release; distribution is unlimited.; The diurnal-period fluctuations of winds and surface currents are analyzed for September 1992 in and around Monterey Bay. Wind records are compared for three coastal stations and two mooring sites. Remotely-sensed surface current observations from two CODAR (HF radar) sites are used to explore the ocean's response to diurnal-period forcing. An average diurnal cycle is formed at each wind station and at all CODAR bins. The earliest sea breeze response is seen at the coastal wind stations where morning winds accelerate toward the coastal mountain ranges. A few hours later, the coastal winds accelerate to the southeast down the Salinas Valley. Offshore afternoon winds rotate from their normal alongshore orientation to also become aligned with the valley. The CODAR-derived surface currents respond in less than the two-hour sampling rate to the onset of the diurnal onshore winds. Currents accelerate in the direction of the Salinas Valley. As the day progresses, the more offshore currents rotate clockwise out from under the winds in a possible Ekman or inertial adjustment that continues throughout the night and spreads onshore. In the afternoon, a complicated eddy pattern develops near shore in a possible response to the coastal boundary.; Lieutenant Commander...

Shadows, currents and AdS fields

Metsaev, R. R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.27%
Conformal totally symmetric arbitrary spin currents and shadow fields in flat space-time of dimension greater than or equal to four are studied. Gauge invariant formulation for such currents and shadow fields is developed. Gauge symmetries are realized by involving the Stueckelberg fields. Realization of global conformal boost symmetries is obtained. Gauge invariant differential constraints for currents and shadow fields are obtained. AdS/CFT correspondence for currents and shadow fields and the respective normalizable and non-normalizable solutions of massless totally symmetric arbitrary spin AdS fields is studied. The bulk fields are considered in modified de Donder gauge that leads to decoupled equations of motion. We demonstrate that leftover on-shell gauge symmetries of bulk fields correspond to gauge symmetries of boundary currents and shadow fields, while the modified de Donder gauge conditions for bulk fields correspond to differential constraints for boundary conformal currents and shadow fields. Breaking conformal symmetries, we find interrelations between the gauge invariant formulation of the currents and shadow fields and the gauge invariant formulation of massive fields.; Comment: v3: 31 pages, RevTeX4. Appendix D devoted to modified de Donder gauge in AdS(d+1) x S(d+1) added. Footnotes 10...

Buoyancy driven rotating boundary currents

Yecko, P. A.; Meacham, S. P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/07/1997
Relevância na Pesquisa
46.25%
The structure of boundary currents formed from intermediately dense water introduced into a rotating, stably stratified, two-layer environment is investigated in a series of laboratory experiments, performed for Froude numbers ranging from 0.01 to 1. The thickness and streamwise velocity profiles in quasi-steady currents are measured using a pH activated tracer (thymol blue) and found to compare favorably to simplified analytic solutions and numerical models. Currents flowing along sloping boundaries in a stratified background exhibit robust stability at all experimental Froude numbers. Such stability is in sharp contrast to the unequivocal instability of such currents flowing against vertical boundaries, or of currents flowing along slopes in a uniform background. The presence of a variety of wave mechanisms in the ambient medium might account for the slower and wider observed structures and the stability of the currents, by effecting the damping of disturbances through wave radiation.; Comment: 9 pages with 2 figures to appear in Ann NYAS "Long range effects in physics and astrophysics"

A study on boundary separation in an idealized ocean model

Düben, Peter D.; Korn, Peter
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/07/2015
Relevância na Pesquisa
36.08%
In numerical ocean models coast lines change the direction from one grid cell to its neighbor and the value for viscosity is set to be as small as possible. Therefore, model simulations are not converged with resolution and boundary separation points differ in essential properties from flow separation in continuous flow fields. In this paper, we investigate the quality of the representation of boundary separation points in global ocean models. To this end, we apply well established criteria for boundary separation within an idealized ocean model setup. We investigate an eddy-resolving as well as a steady test case with idealized and unstructured coast lines in a shallow water model that is based on a finite element discretization method. The results show that well established criteria for separation fail to detect boundary separation points due to an insufficient representation of ocean flows along free-slip boundaries. Along no-slip boundaries, most separation criteria provide adequate results. However, a very sophisticated criterion based on dynamical system theory reveals that the representation of boundary separation is limited for these flows as well. We conclude that the representation of boundary separation points in numerical ocean models is not satisfying. This will have an impact on the separation of boundary currents in global ocean models.

The representation of boundary currents in a finite element shallow water model

Düben, Peter D.; Korn, Peter
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/02/2015
Relevância na Pesquisa
46.29%
We evaluate the influence of local resolution, eddy viscosity, coastline structure, and boundary conditions on the numerical representation of boundary currents in a finite element shallow-water model. The use of finite element discretization methods offers a higher flexibility compared to finite difference and finite volume methods, that are mainly used in previous publications. This is true for the geometry of the coast lines and for the realization of boundary conditions. For our investigations we simulate steady separation of western boundary currents from idealized and realistic coast lines. The use of grid refinement allows a detailed investigation of boundary separation at reasonable numerical cost.

Use of recent geoid models to estimate mean dynamic topography and geostrophic currents in South Atlantic and Brazil Malvinas confluence

Lopes, Alexandre Bernardino; Harari, Joseph
Fonte: Universidade de São Paulo. Instituto Oceanográfico Publicador: Universidade de São Paulo. Instituto Oceanográfico
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; Formato: application/pdf
Publicado em 01/01/2012 ENG
Relevância na Pesquisa
46.12%
The use of geoid models to estimate the Mean Dynamic Topography was stimulated with the launching of the GRACE satellite system, since its models present unprecedented precision and space-time resolution. In the present study, besides the DNSC08 mean sea level model, the following geoid models were used with the objective of computing the MDTs: EGM96, EIGEN-5C and EGM2008. In the method adopted, geostrophic currents for the South Atlantic were computed based on the MDTs. In this study it was found that the degree and order of the geoid models affect the determination of TDM and currents directly. The presence of noise in the MDT requires the use of efficient filtering techniques, such as the filter based on Singular Spectrum Analysis, which presents significant advantages in relation to conventional filters. Geostrophic currents resulting from geoid models were compared with the HYCOM hydrodynamic numerical model. In conclusion, results show that MDTs and respective geostrophic currents calculated with EIGEN-5C and EGM2008 models are similar to the results of the numerical model, especially regarding the main large scale features such as boundary currents and the retroflection at the Brazil-Malvinas Confluence.; A utilização de modelos geoidais na determinação da Topografia Dinâmica Média foi impulsionada com o lançamento dos satélites do sistema GRACE...

Potential vorticity dynamics of boundary currents in a quasigeostrophic ocean.

Lozier, Susan; Riser, S.C.
Fonte: Journal of Physical Oceanography Publicador: Journal of Physical Oceanography
Tipo: Artigo de Revista Científica
Publicado em //1989
Relevância na Pesquisa
36.07%
Boundary layer potential vorticity dynamics for a quasi-geostrophic, eddy-resolving general circulation ocean model are studied using both Lagrangian and Eulerian analyses. Active western boundary layers are found not only in the upper wind-driven layer but also in the lower layers, despite the lack of a direct vorticity input to the deep ocean. At the western wall dissipative and inertial boundary regimes are exclusively controlled by the time-mean dynamics except for the deepest layer where eddy fluxes drive the mean flow across mean potential vorticity contours. Boundary layers formed at the southern wall in this model are dynamically distinct from the western boundary layers; they are controlled solely by the eddy flux of potential vorticity found in this region of active baroclinic instability. Basin-integrated vorticity balances reveal a strong contribution to the vorticity cycle by the lateral boundaries with such input overshadowed by the vorticity exchange across the midbasin gyre boundary in the surface layer.

Reconstruction of Sea-Surface Temperatures from Assemblages of Planktonic Foraminifera: Multi-Technique Approach Based on Geographically Constrained Calibration Data Sets and its Application to Glacial Atlantic and Pacific Oceans

Kucera, Michal; Weinelt, Mara; Kiefer, T; Pflaumann, U; Hayes, Angela; Weinelt, Martin; Chen, Min-Te; Mix, Alan C.; Barrows, Timothy; Cortijo, E; Duprat, Josette; Juggins, Steve; Waelbroeck, Claire
Fonte: Pergamon-Elsevier Ltd Publicador: Pergamon-Elsevier Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
36.11%
We present a conceptual framework for a new approach to environmental calibration of planktonic foraminifer census counts. This approach is based on simultaneous application of a variety of transfer function techniques, which are trained on geographically constrained calibration data sets. It serves to minimise bias associated with the presence of cryptic species of planktonic foraminifera and provides an objective tool for assessing reliability of environmental estimates in fossil samples, allowing identification of adverse effects of no-analog faunas and technique-specific bias. We have compiled new calibration data sets for the North (N=862) and South (N=321) Atlantic and the Pacific Ocean (N=1111). We show evidence that these data sets offer adequate coverage of the Sea-Surface Temperature (SST) and faunal variation range and that they are not affected by the presence of pre-Holocene samples and/or calcite dissolution. We have applied four transfer function techniques, including Artificial Neural Networks, Revised Analog Method and SIMMAX (with and without distance weighting) on faunal counts in a Last Glacial Maximum (LGM) data set for the Atlantic Ocean (748 samples in 167 cores; based on the GLAMAP-2000 compilation) and a new data set for the Pacific Ocean (265 samples in 82 cores) and show that three of these techniques provide adequate degree of independence for the advantage of a multi-technique approach to be realised. The application of our new approach to the glacial Pacific lends support to the contraction and perhaps even a cooling of the Western Pacific Warm Pool and a substantial (>3°C) cooling of the eastern equatorial Pacific and the eastern boundary currents. Our results do not provide conclusive evidence for LGM warming anywhere in the Pacific. The Atlantic reconstruction shows a number of robust patterns...