The laser geodetic satellites Lageos and Starlette exhibit residual orbital motion with an unexplained seasonal component. In addition, recognized polar motion excitation sources do not account for a large portion of observed polar motion. It is hypothesized that air and ocean mass redistribution is the primary source of seasonal perturbations in satellite motion, and that wind-driven ocean mass redistribution is a major source for polar motion excitation. Average monthly variations in zonal spherical harmonic geopotential coefficients are estimated from NMC air pressure for 1958 through 1973, and from variations in continental water storage predicted by a global hydrologic model. These coefficients are used to predict average monthly perturbations in the longitude of the ascending node ([Omega]) for Lageos and Starlette, and in the eccentricity vector ([Psi]) for Starlette. WMO monthly air pressures and twice-daily Navy sea level pressures are used to predict time series of [Omega] and [Psi] perturbations for Lageos during 1976 through 1985, and for Starlette during 1980 through 1983. In addition, the Hellerman and Rosenstein wind stress field for world oceans and the Gill-Niiler bottom pressure equation are used to estimate annual and semi-annual ocean mass redistribution, and to predict polar motion excitation vectors and Lageos [Omega] perturbations. Comparison of predicted [Omega] and [Psi] perturbations with observed Lageos and Starlette behavior indicate that air pressure may be responsible for much of the unmodeled seasonal variation in the Earth's geopotential. In contrast, the water storage contribution is very small. Year-to-year variability in the observed Lageos and Starlette [Omega] times series is well matched by predicted perturbations. Even after the removal of annual and semi-annual components, significant coherence remains between predicted and observed [Omega] time series for both Lageos and Starlette at periods of less than one year. Comparison of predicted polar motion with ILS observations suggest that the effect of ocean mass redistribution is significant, and second only to air pressure in magnitude. Lageos [Omega] perturbations predicted from ocean mass redistribution indicate that non-isostatic sea level fluctuations should be readily observable by satellite laser ranging. / text

No description available.

Thesis (Ph.D.)--Flinders University, School of Chemistry, Physics and Earth Sciences. / Typescript bound. Includes bibliographical references: (leaves167-173) Also available online.

Thesis (Ph. D.)--Ohio State University, 2008.

Made available in DSpace on 2015-06-17T19:33:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-03-24. Added 1 bitstream(s) on 2015-06-18T12:47:40Z : No. of bitstreams: 1 000825926.pdf: 7141282 bytes, checksum: 32bb0e8b499321c636f40eef71e9f402 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Fundação para o Desenvolvimento da UNESP (FUNDUNESP) / FAPESP: 2009/54672-4 / FUNDUNESP: 1214/2010-DFP

Orientador: Adilson Fransozo / Coorientador: Fúlvio Aurélio de Morais Freire / Banca: Gustavo Monteiro Teixeira / Banca: Giovana Bertini / Banca: Valter José Gobo / Banca: Rogério Caetano da Costa / Resumo: Não disponível / Abstract: Not available / Doutor

A formação de águas profundas na Antártica afeta diretamente o clima global, uma vez que este processo conecta os ramos superior e inferior da circulação termohalina global (MOC). Avaliar os impactos das mudanças climáticas nestes processos é importante para compreensão do transporte global de calor pelos oceanos e para realização de projeções climáticas. Aplicando a forçante interanual Coordinated Ocean-Ice Reference (CORE), foi realizada uma simulação de 60 anos (1948-2007) utilizando o ROMS com módulos de gelo marinho e plataforma de gelo ativos. Uma rodada preliminar de 100 anos foi realizada com forçante do ano normal CORE, para gerar campos estáveis de inicialização da rodada interanual. Para ambos os experimentos adotou-se uma grade circumpolar periódica com resolução variável, alcançando cerca de 5 km na borda sul. Para investigar as massas de água foi aplicada a Análise Multiparamétrica Ótima - OMP. As principais massas de água do Mar de Ross foram identificadas: Água de Superfície Antártica (AASW), Água Circumpolar Profunda (CDW), Água de Fundo Antártica (AABW) e Água de Plataforma (SW), posteriormente separadas em Água da Plataforma de Gelo (ISW) e Água de Plataforma de Alta Salinidade (HSSW). Os resultados são consistentes com observações prévias (Bergamasco, 2002; Orsi & Wiederwohl, 2009; Budillon, 2011). A simulação interanual sugere que o Oceano Austral vem sofrendo um processo de aquecimento e diminuição de salinidade. Houve um aumento do calor advectado pela CDW e uma diminuição da salinidade das águas de plataforma e da AABW, consistente com as observações de Johnson & Doney (2006). A capacidade do modelo regional ROMS de reproduzir as águas de plataforma ISW, HSSW e a AABW é uma importante contribuição para estudos climáticos, visto que os modelos globais não conseguem representar tais processos. A inclusão de parametrizações explícitas dos processos de gelo marinho e plataforma de gelo capacita o ROMS para reproduzir os processos associados a criosfera, possibilitando a obtenção de projeções mais realísticas. / Dense water formation around Antarctica is recognized as a significant process that significantly impacts the global climate, since that\'s where the linkage between the upper and lower limbs of Global Thermohaline Circulation takes place. Assessing whether these processes may be affected by rapid climate changes and all the eventual feedbacks is crucial to fully understand the ocean heat transport and to provide quality future climate projections. Applying the Coordinated Ocean-Ice Reference (CORE) interannual forcing we have run a 50-year simulation (1948-2007) using ROMS with a new sea ice/ice shelf thermodynamics module. Another 100-year simulation forced with CORE normal year was previously run to provide stable starting fields. The normal year consists of single annual cycle of all the data that are representative of climatological conditions over decades and can be applied repeatedly for as many years of model integration as necessary. The 60-year forcing has interannually varying data from 1948 to 2007, which allows validation of model output with ocean observations. Both experiments employed a periodic circumpolar variable resolution grid reaching less than 5 km at the southern border. By applying the OMP water masses separating scheme, we were able to identify the main Ross Sea water masses: Antarctic Surface Water (AASW), Circumpolar Deep Water (CDW), Antarctic Bottom Water (AABW) and Shelf Water (SW), further separated into Ice Shelf Water (ISW) and High Salinity Shelf Water (HSSW). Results are consistent with previous observational studies (Bergamasco, 2002; Orsi & Wiederwohl, 2009; Budillon, 2011). The interannual simulation indicates that the Southern Ocean is becoming warmer and less salty. The CDW poleward heat transport increased while shelf waters salinity as well as the AABW salinity decreased during the simulation period, consistent with Johnson & Doney (2006), who have reported the export of less dense AABW. ROMS capability to represent ISW, HSSW and AABW is an important contribution to climate studies, since IPCC class models seem unable to provide reliable representations of such important processes, which may lead to projections of more realistic scenarios. This is significantly improved in this study by including more explicit sea ice/ice shelf parameretization. ROMS is able to reproduce cryosphere-linked mechanisms of dense water formation around Antarctica.

A formação de águas profundas na Antártica afeta diretamente o clima global, uma vez que este processo conecta os ramos superior e inferior da circulação termohalina global (MOC). Avaliar os impactos das mudanças climáticas nestes processos é importante para compreensão do transporte global de calor pelos oceanos e para realização de projeções climáticas. Aplicando a forçante interanual Coordinated Ocean-Ice Reference (CORE), foi realizada uma simulação de 60 anos (1948-2007) utilizando o ROMS com módulos de gelo marinho e plataforma de gelo ativos. Uma rodada preliminar de 100 anos foi realizada com forçante do ano normal CORE, para gerar campos estáveis de inicialização da rodada interanual. Para ambos os experimentos adotou-se uma grade circumpolar periódica com resolução variável, alcançando cerca de 5 km na borda sul. Para investigar as massas de água foi aplicada a Análise Multiparamétrica Ótima - OMP. As principais massas de água do Mar de Ross foram identificadas: Água de Superfície Antártica (AASW), Água Circumpolar Profunda (CDW), Água de Fundo Antártica (AABW) e Água de Plataforma (SW), posteriormente separadas em Água da Plataforma de Gelo (ISW) e Água de Plataforma de Alta Salinidade (HSSW). Os resultados são consistentes com observações prévias (Bergamasco, 2002; Orsi & Wiederwohl, 2009; Budillon, 2011). A simulação interanual sugere que o Oceano Austral vem sofrendo um processo de aquecimento e diminuição de salinidade. Houve um aumento do calor advectado pela CDW e uma diminuição da salinidade das águas de plataforma e da AABW, consistente com as observações de Johnson & Doney (2006). A capacidade do modelo regional ROMS de reproduzir as águas de plataforma ISW, HSSW e a AABW é uma importante contribuição para estudos climáticos, visto que os modelos globais não conseguem representar tais processos. A inclusão de parametrizações explícitas dos processos de gelo marinho e plataforma de gelo capacita o ROMS para reproduzir os processos associados a criosfera, possibilitando a obtenção de projeções mais realísticas. / Dense water formation around Antarctica is recognized as a significant process that significantly impacts the global climate, since that\'s where the linkage between the upper and lower limbs of Global Thermohaline Circulation takes place. Assessing whether these processes may be affected by rapid climate changes and all the eventual feedbacks is crucial to fully understand the ocean heat transport and to provide quality future climate projections. Applying the Coordinated Ocean-Ice Reference (CORE) interannual forcing we have run a 50-year simulation (1948-2007) using ROMS with a new sea ice/ice shelf thermodynamics module. Another 100-year simulation forced with CORE normal year was previously run to provide stable starting fields. The normal year consists of single annual cycle of all the data that are representative of climatological conditions over decades and can be applied repeatedly for as many years of model integration as necessary. The 60-year forcing has interannually varying data from 1948 to 2007, which allows validation of model output with ocean observations. Both experiments employed a periodic circumpolar variable resolution grid reaching less than 5 km at the southern border. By applying the OMP water masses separating scheme, we were able to identify the main Ross Sea water masses: Antarctic Surface Water (AASW), Circumpolar Deep Water (CDW), Antarctic Bottom Water (AABW) and Shelf Water (SW), further separated into Ice Shelf Water (ISW) and High Salinity Shelf Water (HSSW). Results are consistent with previous observational studies (Bergamasco, 2002; Orsi & Wiederwohl, 2009; Budillon, 2011). The interannual simulation indicates that the Southern Ocean is becoming warmer and less salty. The CDW poleward heat transport increased while shelf waters salinity as well as the AABW salinity decreased during the simulation period, consistent with Johnson & Doney (2006), who have reported the export of less dense AABW. ROMS capability to represent ISW, HSSW and AABW is an important contribution to climate studies, since IPCC class models seem unable to provide reliable representations of such important processes, which may lead to projections of more realistic scenarios. This is significantly improved in this study by including more explicit sea ice/ice shelf parameretization. ROMS is able to reproduce cryosphere-linked mechanisms of dense water formation around Antarctica.

La dorsale de Reykjanes est une structure topographique majeure de l’océan Atlantique Nord qui s’étend de l’Islande à la zone de fracture de Charlie Gibbs. Située entre le bassin d’Islande et la mer d’Irminger, la dorsale de Reykjanes influence fortement la circulation du gyre subpolaire et est une porte d’entrée vers les zones de convection profondes. Cependant, la circulation et la répartition des masses d’eau à travers la dorsale de Reykjanes n’ont jamais été directement quantifiées, de sorte que la caractérisation de la connexion entre le bassin d’Islande et la mer d’Irminger est encore incomplète. Dans le cadre du projet « Reykjanes Ridge Experiment », nous avons été capables d’analyser la circulation autour, au-dessus et à travers la dorsale de Reykjanes. Essentiellement à partir de sections hydrographiques perpendiculaires et le long de l’axe de la dorsale, l’objectif de cette thèse a été de quantifier et caractériser la circulation 3-D et les propriétés des courants qui longent et traversent la dorsale de Reykjanes. Nous avons commencé par quantifier précisément le transport géostrophique à travers les sections, ce qui a permis d’améliorer le traitement des données S-ADCP. A travers la dorsale de Reykjanes, l’intensité de la branche du gyre subpolaire qui rejoint la mer d’Irminger a été estimée à 21.9 + 2.5 Sv en Juin – Juillet, avec des intensifications dans la zone de fracture Bight (BFZ) et à 59 – 62°N. Dans la BFZ, les masses d’eau profondes sont influencées par la bathymétrie, de sorte que leurs propriétés hydrologiques se modifient lorsqu’elles traversent la dorsale de Reykjanes. Enfin, la bathymétrie et la circulation horizontale cyclonique du bassin d’Islande contrôlent les courants qui longent la dorsale en bloquant certaines masses d’eau, et donc sont à l’origine de la répartition de ces masses d’eau le long de la dorsale. En plus des masses d’eau du Bassin d’Islande, le Courant d’Irminger comprend également des masses d’eau qui proviennent de la mer d’Irminger. / The Reykjanes Ridge is a major topographic feature of the North-Atlantic Ocean that extends from Iceland to the Charlie Gibbs Fracture Zone. Located between the Iceland Basin and the Irminger Sea, the Reykjanes Ridge strongly influences the subpolar gyre circulation and is a gate toward the deep convection areas. However, the circulation and distribution across the Reykjanes Ridge has never been directly quantified such that the characterization of the connection between the Iceland Basin and the Irminger Sea is still incomplete. As part of the Reykjanes Ridge Experiment project, we were able to analyze the circulation around, above and across the Reykjanes Ridge. Mainly based on hydrographic sections along and perpendicular to the ridge axis, the aim of this PhD thesis was thus to characterize the 3-D circulation and properties of the flow along and across the Reykjanes Ridge.We started by accurately quantifying geostrophic transports across the sections, which led to improvements in the treatment of S-ADCP data. Across the Reykjanes Ridge, the intensity of the wesward branch of the subpolar gyre was estimated at21.9 + 2.5 Sv in June – July 2015 with intensifications at the Bight Fracture Zone (BFZ) and at 59 – 62°N. At the BFZ, overflow waters are influenced by the bathymetry such as their hydrological properties evolve as they cross the Reykjanes Ridge. Finally, both the bathymetry and the cyclonic horizontal circulation of the Iceland Basin regulate the evoluton of the along-ridge flows by blocking water masses, and thus shaping the water mass distribution over the Reykjanes Ridge. In addition to waters from the crossridge flow, the Irminger Current incorporates waters from the center of the Irminger Sea.

O trabalho aqui apresentado utiliza dados da fugacidade de CO2 (fCO2) coletados por onze cruzeiros oceanográficos no Oceano Atlântico Sudoeste (OAS) que fazem parte do banco de dados do SOCAT para analisar a variabilidade espacial da fCO2 e as principais variáveis relacionadas a suas variações. Foram utilizados dados do satélite AQUA para se estudar a fCO2 sobre os campos médios mensais de temperatura da superfície do mar (TSM) e concentração de clorofila. Também foram utilizados dados de reanálise para descrever os campos de vento e pressão atmosférica em superfície durante o período de cada cruzeiro. Através dos dados de vento em superfície foram calculados os campos de bombeamento de Ekman. Os resultados demonstram que a principal variável responsável pelas variações da fCO2 foi a TSM (em geral com coeficiente de correlação r>0,8) e que as distintas massas d'água na região apresentam diferentes fCO2, sendo que as massas d'água mais quentes apresentam valores mais elevados que as mais frias. As águas da Pluma do Rio da Prata apresentam uma fCO2 que chega a ser ate 1,5 vezes maior que as outras massas d'água. Descreve-se, pela primeira vez no OAS, a importância de se considerarem os padrões de vento em superfície (através do bombeamento de Ekman) e não somente os valores de TSM e concentração de clorofila para uma melhor análise da fCO2 em relação às massas d'água no OAS. / The work presented here uses CO2 fugacity data (fCO2) collected by eleven oceanographic cruises in the Southwestern Atlantic Ocean (SAO) that are part of the SOCAT database to analyze the spatial variability of the fCO2 and the main variables related to its variations. AQUA satellite data were used to study the fCO2 over the monthly averaged sea surface temperature (SST) and chlorophyll concentration fields. Reanalysis data were also used to describe the wind and surface atmospheric pressure fields during the period of each cruise. Through the surface wind data, the Ekman pumping fields were calculated. The results show that the main variable responsible for fCO2 variations was SST (in general with a correlation coefficient r> 0.8) and that the different water masses in the region present different fCO2, with the warmer water masses presenting higher values than the cold ones. The waters of the La Plata Plume present a fCO2 that is up to 1.5 times higher than the other water masses. It is described for the first time in OAS the importance of considering the surface wind patterns (through Ekman pumping) and not only the values of SST and chlorophyll concentration for a better analysis of fCO2 in relation to the water masses in the OAS.