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Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Earth and Planetary Sciences. / Vita. / Bibliography: leaves 324-329. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Vita. / Bibliography : leaves 227-236. / by Mary Josephine Richardson. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 92-98. / by Eric Arthur D'Asaro. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1981. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 95-96. / by Peter Reid Daifuku. / M.S.

Huge amounts of anthropogenic 129I have been and still are released to the environment through liquid and gaseous discharges from the nuclear fuel reprocessing facilities worldwide and in particular the ones in Europe. Most of this 129I signal has been accumulated in the marine environment which plays a major role in the iodine natural pool.  In this thesis, an overview of available 129I concentrations in waters of the oceans and marginal seas together with new data about 129I and 127I spatial distribution in surface seawater along a transect between the North Sea and the northeastern Atlantic Ocean are presented. After comprehensive chemical separation, the concentrations of iodine isotopes (127I and 129I) and their species (iodide and iodate) were analysed using accelerator mass spectrometry and inductively-coupled plasma mass spectrometry. The results show that, generally, changes in the 127I and 127I-/127IO3- are comparable to data from other marine waters which are related to natural distribution patterns. A considerable variation of 129I along the transect is observed with the highest values occurring in the eastern English Channel and relatively low values obtained in the northeastern Atlantic Ocean. Inventory estimations of 129I in the North Sea and the English Channel are 147 kg and 78 kg, respectively, where more than 90% resides in the Southern Bight and the eastern English Channel. Iodate is the dominant iodine species for both 127I and 129I in most seawater samples from the North Sea to the Atlantic Ocean. 129I species variability suggests a slow process of 129I- oxidation in the open sea. It takes at least 10 years for the 129I-/129IO3- pair to reach their natural equilibrium as the water is transported from the English Channel. The results suggest a main transport of 129I from the western English Channel via the Biscay Bay into the northeastern Atlantic Ocean. Further, high 129I/127I and distinctive 129I-/129IO3- values south of 40°N indicate possible contribution of 129I through Mediterranean Outflow Water. The environmental radioactive impact of 129I and possible applications in ecosystem studies are also discussed.

Zooplankton assemblages were examined from waters off the west coast of Scotland encompassing the Firths of Lorn and Clyde, the North Channel, and the Malin Shelf. Size fractionated samples (coarse, >1000μm; medium, 1000μm-330μm; fine, 330μm-180μm) were collected with a submersible pump from 10m and 30m depth in March (1987) and May (1986) providing a composite picture of the fauna in early and late spring conditions, respectively. The feasibility of using image analysis as a method for processing zooplankton samples was examined. Although a programme was successfully operated to obtain individual measurement data, much work is still required before a fully automated programme for routine use by planktologists is available. Total zooplankton numbers and biomass, and species distributions and relative abundances were examined. Species assemblages were identified using multivariate analyses. Biomass and abundance spectra by size were examined for the major station groupings. In general, meroplankton dominated the fauna in the Firth of Lorn while large numbers of Calanus spp. occurred in the Firth of Clyde. Small copepods such as Oithona spp. were characteristic of the assemblage on the Malin Shelf. Salinity, followed by temperature, showed the strongest association with the observed station clusters. Chlorophyll a and depth did not generally appear to influence station groupings. The potential for the mixing and exchange of zooplankton between the regions of the study area was evaluated. The results suggest that zooplankton may be entrained from the Firth of Clyde by the Scottish Coastal Current during the spring period. The Malin Shelf may also be an important source of zooplankton for the Firth of Lorn during winter months when an onshore flow of Atlantic water occurs.

L’objectif de ce travail était d’étudier la variabilité de la circulation océanique méridienne aux échelles de temps pluri décennales dans l’océan Atlantique nord au cours des deux mille dernières années, ainsi que son lien avec la variation de l’extension des gyres subtropicales et subpolaires. J’ai donc étudié, à partir de carottes de sédiments marins à fort taux de sédimentation, l’évolution de la température des eaux de surface et de la stratification de la colonne d’eau en lien avec le fonctionnement des gyres subpolaire et subtropicale.Compte tenu des difficultés spécifiques à la période de temps considérée, la première partie de mon travail a consisté à contraindre le milieu et la période de calcification des principaux foraminifères utilisés, à partir de la composition isotopique de l’oxygène analysée dans la coquille des foraminifères planctoniques. J’ai également précisé la calibration en Magnésium et en Calcium en fonction de la température. La deuxième partie de mon travail a consisté à reconstruire les conditions hydrologiques dans des zones clés de l’océan Atlantique Nord sur les deux mille dernières années. J’ai ainsi construit un index de la gyre subpolaire à partir d’un gradient de température Est-Ouest, qui traduit l’intensité dynamique de la gyre subpolaire et de la gyre subtropicale. L’apport de l’analyse des foraminifères planctoniques profonds a permis de reconstituer les variations de la colonne d’eau supérieure. La stratification plus ou moins marquée de la colonne d’eau est reliée directement à l’intensité des vents d’Ouest. Les similitudes entre les vents et l’index de gyre m’ont amené à proposer un couplage entre l’océan et l’atmosphère aux échelles de temps pluri décennales.La dernière partie de ma thèse s’est focalisée sur les conséquences des variations de la dynamique des gyres océaniques sur le transport de chaleur vers les hautes latitudes ainsi que sur l’impact des variations des vents d’Ouest sur le climat européen. / The purpose of this thesis was to study the surface oceanic circulation in the North Atlantic Ocean during the last 2,000 years, and its link with the intensity of the subpolar and the subtropical gyres. To fulfill these objectives, I studied sediment cores with a high sedimentation rate to reconstruct the multidecadal variability of the temperature and the water column stratification, controlled by the dynamic of oceanic gyres. To improve the marine paleoclimatic signal recorded from planktonic foraminifera, I constrained their growing season and their calcification depth by analyzing the oxygen isotopic composition of their calcitic shells. I also established calibrations between Mg/Ca ratio and temperature for the main species used.I applied these calibrations to reconstruct the hydrological conditions in key areas of the North Atlantic Ocean. I constructed an index of the subpolar gyre that traduces the dynamic intensity of the subpolar gyre and the subtropical gyre. I also studied the variability of the upper water column based on the analysis of deep-dwelling foraminifera. I interpret past changes in the water column stratification as resulting from changes in the intensity of Westerly winds. The similarities between the wind forcing evolution and the index of the subpolar gyre dynamics led me to propose a coupling between the ocean and the atmosphere on the multidecadal time scale. The consequences of the gyres dynamic on heat transport and the impacts of the change in westerly wind strength on European climate are studied in the last part of the manuscript.

A interação entre troposfera e estratosfera tem grande influência e é de grande importância nos processos de ciclogênese em superfície. Entretanto, não se conhece exatamente a frequência destas interações e nem como podem influenciar na intensidade de ciclones em geral. Este trabalho tem como objetivo geral estudar como os altos níveis da atmosfera afetam o desenvolvimento de ciclones em superfície na América do Sul e Oceano Atlântico Sul, utilizando o conceito de vorticidade potencial (VP). Através de dados de ciclones rastreados em superfície e VP em 300 hPa desenvolveu-se um algoritmo que associa automaticamente os ciclones em superfície com anomalias de vorticidade potencial (AVP). Para o período 1998-2003, fez-se então a separação dos ciclones em associados (AAVP) e não-associados (NAVP) a AVP. De forma geral, observou-se que a maior parte dos ciclones AAVP concentra-se na região oceânica extratropical e os NAVP preferencialmente na região continental próximo de 30°S e em latitudes subtropicais. Para todo o período analisado, o número total de ciclones AAVP (55%) superou o número de NAVP (45%), sendo o ano de 2002 o único que apresentou número maior de eventos NAVP. Quanto à distribuição sazonal, os ciclones AAVP são mais frequentes nos meses de inverno e primavera, enquanto que os NAVP nos meses de verão. O tempo de vida dos NAVP é menor que dos AAVP, além de possuírem menor intensidade (de acordo com a pressão central média). Além destes fatores, a distância percorrida e a velocidade médias dos ciclones NAVP são menores do que dos AAVP. As composições dos campos sinóticos mostram que nos eventos NAVP, independente da estação do ano, a troposfera é mais quente que nos AAVP. Nos NAVP a forçante térmica é essencial para a formação do ciclone, enquanto que nos AAVP a AVP induz vorticidade ciclônica primeiro em altos níveis, que então se propaga para baixos níveis. Através da análise dos campos sinóticos, notou-se maior baroclinia nos casos NAVP, pois tanto os cavados em altos e médios níveis quanto a corrente de jato permanecem favorecendo o desenvolvimento do ciclone em superfície, enquanto que nos AAVP o centro do ciclone em superfície está verticalmente quase alinhado ao cavado. Centros de vorticidade relativa ciclônica em 500 hPa desprendem-se do escoamento de oeste em todas as estações para os casos AAVP, porém, no verão, isto também é visto nos NAVP. / The process of troposphere-stratosphere interaction has influence and is very important on surface cyclogenesis. However, the frequency of these interactions and how they influence the intensity of cyclones is not known exactly. The main objective of this work is to study how the upper levels affect the development of surface cyclones in South America and South Atlantic Ocean using the concept of potential vorticity (PV). Cyclone tracking data and 300 hPa PV were used to develop an algorithm that automatically associates the surface cyclones with potential vorticity anomaly (PVA). For the period 1998-2003, the cyclones were separated as associated (APVA) and non-associated (NPVA) with PVA. In general, it was observed that most of the APVA cyclone was concentrated in extratropical oceanic region, while NPVA cyclones form over the continent preferably around 30°S and subtropics. The total number of APVA cyclones (55%) exceeds the number of NPVA (45%), except for 2002. In regard to seasonal distribution, the APVA cyclones are more frequent in winter and spring months while NPVA in summer months. The lifetime of NPVA cyclones is shorter and they are less intense than APVA (according to the average central pressure). In addition to these factors, the mean traveled distance and mean velocity are smaller in the NPVA than in APVA. The composites of the synoptic fields show that in NPVA events, regardless of the season, the troposphere is warmer than in APVA. In NPVA cases the thermal forcing is essential to the cyclogenesis, while in the APVA the cyclonic vorticity induced by PVA at upper levels propagating to low levels is more important. The NPVA cases present more baroclinic characteristics which the upper and mid-level troughs accompanied by the jet stream favoring the surface cyclone development, whereas in the APVA the surface cyclone center remains almost vertically aligned with these troughs. For APVA cases, the centers of cyclonic vorticity at 500 hPa detach from westerly flow in all seasons however in summer this is also seen in NPVA.

Sedimentos de mar profundo são ambientes estáveis e homogêneos, apesar disso, eles apresentam uma grande variedade de habitats disponíveis, possibilitando uma alta diversidade microbiana. A distribuição espacial dos micro-organismos é influenciada por fatores locais e regionais. Os fatores locais são associados à estrutura do ambiente e os fatores regionais, a limitação na dispersão dos micro-organismos que compõem as comunidades e eventos históricos que eventualmente podem modificar o ambiente. Eventos como a liberação de hidrocarbonetos das camadas mais profundas do sedimento para superfície podem alterar os padrões de distribuição espacial das comunidades microbianas, devido o aumento na disponibilidade de carbono e consequentemente selecionando as espécies capazes de degradá-los. Esses eventos são denominados de exsudações de asfalto e foram encontradas na região de estudo. Considerando a falta de conhecimento e a importância dos micro-organismos em sedimentos de mar profundo do oceano Atlântico Sul, o objetivo desse estudo foi compreender os padrões de diversidade microbiana nessas regiões e também investigar como o óleo proveniente da exsudação de asfalto influência as comunidades de micro-organismos no seu entorno. Esse estudo foi realizado na região do Platô de São Paulo que foi dividido em duas regiões, norte e sul. A diversidade microbiana foi estudada em 14 amostras de sedimento de mar profundo, nove amostras na região norte e cinco na sul. A exsudação de asfalto foi encontrada na região norte, influenciando diretamente três das nove amostras. As comunidades foram estudadas através dos métodos de eletroforese em gel de gradiente desnaturante (DGGE), PCR quantitativa (qPCR) e sequenciamento de última geração (Ion Torrent). A distribuição espacial das comunidades foi analisada em diferentes escalas espaciais: verticalmente, variando com a profundidade do sedimento (≤ 4 cm), localmente, em cada uma das regiões amostradas (1-34 Km) e regionalmente, comparando as regiões norte e sul (> 250 Km). O perfil da comunidade obtido com a técnica de DGGE mostrou que as comunidades microbianas foram menos similares entre as regiões e apresentaram relação com a distância geográfica para arqueia e bactéria. Os valores de similaridade foi maior localmente do que regionalmente. A similaridade obtida nas camadas de profundidade analisadas foi alta e não houve relação com a distância geográfica. O número de células entre as camadas de profundidades foi diferente, com tendência de diminuição com o aumento da profundidade. As classes bacterianas mais abundantes foram Alphaproteobacteria (30%), Acidimicrobiia (18%), Gammaproteobacteria (16%), Deltaproteobacteria e Gemmatimonadetes (3%). A composição das comunidades influenciadas pela exsudação de asfalto não teve relação com a presença do óleo ou com as camadas de profundidade. A distância geográfica e a exsudação de asfalto foram importantes fatores para determinação da distribuição geográfica das comunidades microbianas em sedimento marinhos profundos do Platô de São Paulo. Apesar da ausência de relação entre o óleo proveniente da exsudação de asfalto e a composição das comunidades, a alta abundância de Alphaproteobacteria e a importância da distância dentro da região norte são indicativos do aumento da heterogeneidade causado pela exsudação de asfalto. Mais estudos procurando compreender a composição geoquímica dos sedimentos e do óleo são necessários para explicar como esses fatores influenciam a estruturação das comunidades microbianas estudadas. / Deep-sea sediments are stable and homogeneous environments, however, they have a high variety of available habitats, allowing a high microbial diversity to occur. Microbial spatial distribution is determined by local and regional factors. Local factors are associated to environment structure and regional factors, to microbial dispersal limitation and historical events that may cause environmental changes. Historical events such as hydrocarbon emanation from sub-seafloor to seafloor may change the patterns of microbial spatial distribution, due to an increase of carbon, thus, selecting species capable to degrade them. These events are denominated as asphalt seep and they were found on the studied region. Considering the lack of knowledge and the importance of microorganisms on deep-sea sediments from South Atlantic ocean, this study aims to understand the patterns of microbial spatial distribution and how the oil from asphalt seep influence the microbial communities. This study was realized in São Paulo Plateau region. The plateau was divided in two regions, north and south. Microbial diversity was studied from 14 deep-sea sediment samples, nine samples from north region and five from south region. The asphalt seep was found in north region from São Paulo Plateau, directly affecting three of the nine samples. The communities were studied through denaturing gradient gel electrophoresis (DGGE), quantitative PCR (qPCR) and next generation sequencing (Ion Torrent). The spatial distribution of the communities was analyzed at different spatial scales: sediment depth (≤ 4 cm), local (1-34 Km) and regional (> 250 Km). Microbial communities were less similar between regions and showing relation with geographic distance to achaea and bacteria. Similarity values within regions were higher then between them, but the geographic distance was also important to both domains, despite samples being closer. Similarity values between sediment depths were high and have no relation with geographic distance. The cell number between sediment depths was different, with tendency to decrease with depth increase. The most abundant classes were Alphaproteobacteria (30%), Acidimicrobiia (18%), Gammaproteobacteria (16%), Deltaproteobacteria e Gemmatimonadetes (3%). The communities composition influenced by asphalt seep have no relation with oil presence and sediment depths. Geographic distance and asphalt seep were important factors to determine the spatial distribution of microbial communities in deep-sea sediments from São Paulo Plateau. Despite the absence of relation between oil from asphalt seep and communities composition, the high abundance of Alphaproteobacteria and the importance of distance within north region are indicative of heterogeneity increase caused by asphalt seep. More studies aiming to understand the geochemical composition from sediments and oil are necessary to explain how these factors influence the communities structure.