A complexa interação que ocorre entre os processos oceânicos e atmosféricos no Oceano Austral afeta a circulação oceânica global em diferentes camadas. O Mar de Weddell e o Mar de Ross possuem reconhecida importância na formação da Água de Fundo Antártica (AABW). O objetivo principal deste trabalho é caracterizar as massas de água dos Mares de Weddell e Ross, através dos dados mais recentes de reanálise oceânica SODA (Simple Ocean Data Assimilation). Através da técnica de separação de massas de água Análise Multiparamétrica Ótima (AMO) foi possível a identificação de 3 principais massas de água no Mar de Ross: Água Profunda Circumpolar Superior (UCDW), Água Profunda Circumpolar Inferior (LCDW) e Água de Plataforma de Baixa Salinidade (LSSW). A UCDW foi a que apresentou a maior variabilidade, não atingindo a Plataforma de gelo do MR durante os anos de 1950-1974. No Mar de Weddell foi possível a identificação das seguintes massas de água: Água Profunda Cálida (WDW), Água Profunda do Mar de Weddell (WSDW) e Água de Fundo do Mar de Weddell (WSBW). A WDW atingiu valores >70% à 800m. A WSDW possui em seu núcleo valores > 90% entre 2000 e 3500m. A WSBW, apresenta ~100% em profundidades > 4000m. / The complex interaction that occurs between the oceanic and atmospheric processes in the Southern Ocean affects global ocean circulation in different layers. The Weddell and Ross Seas have recognized importance in the formation of Antarctic Bottom Water (AABW). This work aims to characterize the water masses of the Weddell and Ross Seas, using the latest ocean data reanalysis SODA (Simple Ocean Data Assimilation). Through the water masses separation technique, Optimum Multiparameter Analysis (OMP), it was possible to identify three main water masses in Ross Sea: Upper Circumpolar Deep Water (UCDW), Lower Circumpolar Deep Water (LCDW) and Low Salinity Shelf Water (LSSW). UCDW showed the greatest variability, not reaching the Ross Sea Ice Shelf during the years 1950-1974. It was possible to identify the following water masses in Weddell Sea: Warm Deep Water (WDW), Weddell Sea Deep Water (WSDW) and Weddell Sea Bottom Water (WSBW). WDW reached values up to 70% in 800m. WSDW has in its core values > 90% between 2000 and 3500m. WSBW presents a contribution up to 100% at depths > 4000m.

As sociedades e instituições arqueológicas, como as demais organizações científicas, são espaços fundamentais no fomento e na manutenção da rede de intelectuais de sua área de pesquisa. Podem, através da veiculação de suas publicações, apontadas na seção editorial de boletins dessas organizações, reafirmar as tradições arqueológicas ou oferecer perspectivas inovadoras. Analisamos trinta e quatro editoriais das publicações The South African Archaeological Bulletin, Nyame Akuma e Nsi, intentando compreender a formação das múltiplas imagens dos arqueólogos africanos e africanistas na era pós-colonial, entre 1987 e 1993, que, a nosso ver, dar-se-ia diante daquilo que essas sociedades através de seus boletins consolidam. Segundo a ótica de seus editores, os boletins do corpus de nossa pesquisa eram meios de comunicação rápidos e eficientes para cumprir funções de possibilitar que os arqueólogos interagissem, que se informassem sobre o andamento das pesquisas de campo e que fossem comunicados quanto à realização de congressos entre seus pares. Nosso recorte temporal define-se pela circulação concomitante dos três boletins, exceto quanto ao Nsi, que foi, um ano antes, em 1992, assimilado ao Nyame Akuma. Esse recorte temporal, a propósito, foi marcado pelas correntes teóricas da Nova Arqueologia, do Pós-Processualismo, dos estudos pós-coloniais e pela divulgação da pesquisa arqueológica na África e sobre a África em face dessas abordagens. Apontamos a título de conclusão da análise que os boletins, sob o pretexto de favorecer os arqueólogos e a produção científica em arqueologia na África durante esse período, veiculavam, na verdade, as imagens ideais ou mesmo as rechaçadas dos arqueólogos interessados na África. Essas imagens eram construídas nos textos dos editores na prática discursiva que formulavam com temas ligados ao ofício do arqueólogo. / The archaeological societies and institutions, like others scientific organizations, they are fundamental spaces in the encouragement and in the support an intellectual\'s network of the research´s area. They can, through the distribution of its publications, like the newsletters, in the editorial section, to reaffirm traditions or offer innovative perspectives. We analyzed thirty and four editorial texts in The South African Archaeological Bulletin, Nyame Akuma and Nsi, intending to understand structure multiple images\' of Africans and Africanists Archaeologists in the post-colonial era, between 1987 and 1993, that, in our opinion, would it is happen before of that societies through its newsletters consolidate. According to the viewpoint their editors, the newsletters of our documental corpus were agile and efficient to fulfill the functions to make possible archaeologists interact, they knew about the fieldwork\'s progress, they were informed about the realization of Congress. Our temporal period is defined by the concomitant movement of the bulletins, with the exception of the year 1993, when Nsi was assimilated to Nyame Akuma. It\'s a period was marked by New Archaeology´s theoretical currents, Post-processualism, postcolonial studies and dissemination of archaeological research in the Africa and about the Africa in face of these approaches. We point as conclusion of the analysis like the bulletins, under the pretext of promoting the archaeologists and the scientific archeology in the Africa, during in this period, they conveyed, in fact, the ideal or rejected images of the interested archaeologists in Africa. These images were constructed in the editor\'s texts in discursive practice that they formulated. They were recurring statements of the contingent themes at the archaeologist´s work.

Submitted by Biblioteca de Pós-Graduação em Geoquímica BGQ (bgq@ndc.uff.br) on 2016-03-28T16:36:04Z No. of bitstreams: 1 Dissertação - Beatriz Andrade da Silva Marques.pdf: 4181094 bytes, checksum: 0f82a71603a769606e160fbeabb2e770 (MD5) / Made available in DSpace on 2016-03-28T16:36:04Z (GMT). No. of bitstreams: 1 Dissertação - Beatriz Andrade da Silva Marques.pdf: 4181094 bytes, checksum: 0f82a71603a769606e160fbeabb2e770 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Química. Programa de Pós-Graduação em Geociências-Geoquímica. Niterói, RJ / O vulcanismo é um potencial agente fertilizador de via eólica para os oceanos. Para as últimas décadas, o sensoriamento remoto tem sido uma ferramenta importante no sentido de avaliar em tempo quase-real alterações de parâmetros nos oceanos durante os episódios de erupção vulcânica, em geral com alta resolução temporal e espacial. Evidências experimentais ainda são pouco reportadas, sobretudo para o hemisfério sul. Este trabalho investiga a resposta biológica decorrente do aporte das cinzas expelidas durante o evento eruptivo de 2011 do complexo vulcânico andino Puyehue-Cordón Caulle em águas do Atlântico Sul / Oceano Austral. Duas abordagens foram empregadas no estudo: (1) sensoriamento remoto orbital; e (2) experimento de fertilização em microcosmo. A investigação feita por meio de sensoriamento remoto utilizou os parâmetros satelitais Espessura Óptica de Aerossol (AOT), Concentração de Clorofila-a (CHL-a) e Temperatura da Superfície do Mar (SST), aquisitados pelo sensor MODIS/Aqua e acessados através do portal Ocean Color mantido pelo OBPG/NASA. O contexto pós-erupção foi avaliado comparando os valores dos parâmetros para o ano (2011) com o valor da série histórica criada com dados de 2002 à 2010. O bioensaio de fertilização foi realizado com as cinzas vulcânicas do evento eruptivo em questão, com tréplicas do controle e outros três tratamentos, distintos em massa de cinzas inserida, em águas coletadas no centro da Passagem de Drake. Os resultados obtidos a partir das duas abordagens deste trabalho, sensoriamento remoto e bioensaio, não são taxativos sobre o acoplamento entre a deposição das cinzas da erupção do complexo vulcânico Puyehue-Cordón Caulle e a possível ocorrência de um evento de fertilização oceânica. Através da análise por sensoriamento remoto é possível notar para o período de intensificação dos ventos de oeste do mesmo ano – primavera-verão – que há picos nas medidas de espessura óptica da atmosfera e de concentração de clorofila, que atingem valores maiores que a média histórica. Isto indica que houve aporte de material continental e que este foi suficiente para propiciar maior desenvolvimento algal no oceano. Estes resultados indicam que a poeira mineral, constituída por material de erosão continental com a contribuição dos depósitos de composições distintas de cinzas expelidas nas diversas erupções andinas, é capaz de prover micronutrientes escassos na coluna d’água ao fitoplâncton, com aumento de biomassa algal de uma comunidade fitoplanctônica não limitada por outros parâmetros (condições de irradiação suficiente, temperaturas menos baixas, camadas de mistura mais rasas e pressão de predação menos intensa). A hipótese também poderia esclarecer a falta de resultados conclusivos do bioensaio feito apenas com as cinzas, sem qualquer beneficiamento de outras fontes continentais / Volcanism is a potential agent for fertilizing by wind the oceans. In the last decades, remote sensing has been an important tool that allows evaluations of near-real-time changes in oceanographic parameters during episodes of volcanic eruptions, in general with high temporal and spatial resolution. Experimental evidences are still poorly reported, especially for the southern hemisphere. This work investigates the biological response resulting from the input of ash expelled during the 2011 eruptive event of the Andean volcanic complex Puyehue-Cordón Caulle over waters of the Atlantic Ocean / Southern Ocean. Two approaches were employed in the study: (1) remote sensing; and (2) fertilization experiment. The research carried out by means of remote sensing, used the satellite parameters Aerosol Optical Thickness (AOT), Concentration of Chlorophyll-a (CHL-a) and Sea Surface Temperature (SST), acquired by MODIS / Aqua and accessed through the Ocean Color portal maintained by OBPG / NASA. The context of post-eruption was assessed by comparing the values of the parameters for the year (2011) with the value of climatology created with data from 2002 to 2010. The fertilization bioassay was performed with volcanic ash from the considered eruption event, with rejoinders of four treatments, different in volume, in water collected in the Drake Passage. The results from the two approaches this work, remote sensing and bioassay, are not exhaustive of the coupling between the deposition of ash from the eruption of the Puyehue-Cordón volcanic complex Caulle and the possible occurrence of an ocean fertilization event. Through remote sensing analysis it is possible to note that, with the intensification period of westerly winds of the same year - spring and summer, there are peaks in aerosol optical thickness measurements of the atmosphere and in concentration of chlorophyll, which reach values higher than the historical average. This indicates that there has been input of continental material, and that this was sufficient to provide greater algal development in the ocean. These results indicate that the mineral dust, formed by continental erosion material with the contribution of deposits of different compositions of ash expelled in several Andean rash, is capable of providing scarce micronutrients in the water column to phytoplankton, with an increase of algal biomass in a phytoplankton community not limited by other parameters (sufficient irradiation conditions, less low temperatures, shallower mixing layers and less intense predation pressure). The hypothesis could also explain the lack of conclusive bioassay results done only with the ashes without any contribution of other continental sources

En raison de leur ubiquité dans les assemblages archéologiques et les collections ethnographiques, les lames d’herminette en pierre ont longtemps été utilisées comme « fossiles-directeurs » afin de mettre en évidence des corrélations typo-chronologiques en Océanie. Néanmoins, les critères d’observations formels utilisés dans cette approche typologique ne permettaient pas de rendre compte de la complexité des processus techniques de fabrication. Après avoir rappelé les autres études expérimentales réalisées précédemment dans la région, nous proposons un premier référentiel des stigmates de taille sur roches basaltiques qui nous permet d’identifier différentes techniques de percussion utilisées dans la confection des lames d’herminette en pierre. La restitution des activités techniques qui ont abouti à la production de ces outils a été réalisée à travers l’analyse technologique d’assemblages archéologiques (produits finis ou semi-finis et déchets de taille) récoltés dans différentes sites de la côte Nord de l’île de Tubuai (Archipel des Australes, Polynésie Française). La caractérisation géochimique des gîtes géologiques et des artefacts taillés découverts en contexte archéologique a permis de restituer la répartition spatiale des différentes séquences de production au sein d’une même communauté ainsi que les transferts d’objets produits dans d’autres archipels. Parmi les différents réseaux d’approvisionnement identifiés dans l’île, j’ai choisi de suivre les activités techniques présentes au sein de deux sites : le premier est un complexe spécialisé dans la production des outils en pierre associant carrière d’extraction et ateliers de transformation, et l’autre un site d’habitat côtier.A travers la restitution des dynamiques de production, d’entretien et d’échange des lames d’herminettes en pierre, nous proposons un nouveau regard sur l’économie traditionnelle des chefferies de Polynésie centrale. Dans les assemblages étudiés, la confection de lames d’herminette a été essentiellement réalisée à travers la production d’éclats utilisés comme supports et transformés par façonnage. Cette combinaison des processus de débitage et de façonnage semble correspondre à une tradition technique qui prend son origine en Polynésie occidentale et qui est identifiée dans tous les archipels de Polynésie orientale. A partir des collections étudiées à Tubuai, il est possible de distinguer une production très standardisée de grandes lames au sein des ateliers spécialisés, et une production très peu standardisée de petites lames au sein des habitats côtiers. Grâce à la restitution des processus de production existant au sein d’une même communauté et des échanges intercommunautaires effectués à longue distance, nous discutons le rôle économique des herminettes à lame de pierre dans les chefferies polynésiennes. / The ubiquity of stone adze blades in archaeological sites and museum collections resulted in their use as “cultural fossils” to draw cultural evolutionary changes in the Polynesian islands. The typological approach proves useful for understanding the archaeological diversity in Oceania. Yet, it lacks efficiency when it comes to shedding light on the technical and economic choices involved in the production processes.After a discussion of previous knapping experimentations performed in Polynesia, I propose a panel of diagnostic criteria for identifying the use of hard and soft hammerstone in the manufacture of adze blades. Then, I focus on the production of blades from assemblages collected on the North coast of Tubuai Island (Austral Archipelago, French Polynesia). Along with the need to consider the whole manufacturing process and the post-production exchange networks comes the necessity to connect different archaeological assemblages. Geochemical characterisation of the geological sources and artefacts discovered within archaeological contexts were used to settle the favoured framework for understanding the series of production sequences and for identifying the transfer of tools produced within and outside the island. Among the different supply networks identified on the island, I chose to investigate the operational sequences located within two sites: a quarry complex involving several workshops and a coastal dwelling site.Through the investigation of manufacture, maintenance and exchange processes regarding stone adze blades, I propose a new insight on the economic system in the chiefdoms of central Polynesia. The technical tradition documented on Tubuai is related to the production and transformation of flakes used as blanks for adze blades manufacture. This association of flaking and shaping processes originated in Western Polynesia but was also spread over Eastern Polynesia. The size and the form of these adzes were directly linked to one’s capacity for producing standard-sized blanks and for shaping specific blades forms. Based on the Tubuai collections, I identified a highly standardised production related to specialist knappers’ workshops, as well as a production of heterogeneous forms of small adze blades within a non-specialised dwelling context. Thanks to the analysis of the production processes within the community and the long-distance intercommunity exchanges, I finally discuss the economic role of stone adzes in ancient Polynesian chiefdoms.

Le stade juvénile chez les animaux demeure souvent une période mystérieuse aux yeux des scientifiques. La survie juvénile est pourtant un facteur déterminant du futur des populations. Les animaux juvéniles sont connus pour leur mortalité importante durant les premiers mois après l’indépendance et leur taux de survie augmente avec l’âge. La théorie suppose d’une part que les juvéniles ont des capacités de survie moindres que celles des adultes. Ils seraient peu efficaces dans leur recherche de nourriture et auraient besoin d’une période d’apprentissage pour être capables de supporter les couts associés à la reproduction. De plus, des facteurs proximaux telles que les fluctuations environnementales et la compétition affectent également la survie des juvéniles. Des études sur les oiseaux terrestres, ont permis d’obtenir de nombreuses informations grâce à la possibilité de faire des observations directes et récemment des études télémétriques. Cependant collecter des données en milieu marin s’avère compliqué, en particulier lorsque l’on s’intéresse aux juvéniles. Les oiseaux marins longévifs ont en commun la longue durée de leur période d’immaturité (jusqu’à plus de 10 ans). Les jeunes, à l’indépendance, se dispersent seuls en mer durant plusieurs années, ne revenant à terre que pour se reproduire une fois adulte. Ainsi, les suivre durant leurs premiers mois afin de comprendre leurs comportements et leur écologie alimentaire constitue un véritable défi. Dans ce contexte, cette thèse a pour objectif d’élucider au moins en partie le mystère de la vie juvénile des oiseaux marins. Grâce à des technologies bio-télémétriques nous avons pu suivre par satellite un large panel de juvéniles de neuf espèces proches d’albatros et pétrels (procellariiformes) se reproduisant dans les Terres Australes et Antarctiques Françaises de l’Océan Austral : les îles Crozet, Kerguelen et Amsterdam. Les trajectoires ont été analysées grâce à différentes méthodes statistiques permettant de décrire les mouvements, le comportement alimentaire et les répartitions spatiales des jeunes après leur envol, le tout en lien avec les conditions environnementales. Les résultats obtenus sont discutés à la lumière de la comparaison avec les adultes des mêmes espèces. Grâce à ce jeu de données j’ai étudié les stratégies de dispersion des jeunes inexpérimentés qui quittent le nid. J’ai montré que ces stratégies ainsi que la proportion d’inné les contrôlant sont très variables selon les espèces et suivent ou non celles des parents selon les espèces. Le taux de variabilité dans les stratégies juvéniles peut refléter leur potentielle plasticité et leur capacité à répondre à des changements de l’environnement et in fine affecter la dynamique des populations. Par ailleurs, l’analyse de trajectoires de juvéniles de grand albatros a révélé qu’en plus de leurs capacités innées ils apprennent très rapidement les compétences de base requises pour survivre en mer puis optimiser leur recherche alimentaire. Cependant des différences perdurent par rapport aux adultes, suggérant que d’autres comportements non-observables (via nos données) nécessitent une période d’apprentissage plus longue. Enfin, quelle que soit la stratégie adoptée, elle semble en partie contrainte par la compétition intraspécifique avec les individus plus âgés puisque les juvéniles limitent celle-ci via une ségrégation spatiale. Ce dernier point souligne le besoin de prendre en compte la répartition spatio-temporelle âge-dépendante des espèces lorsque l’on veut mettre en œuvre des mesures de protection pour ces espèces. Ces travaux apportent de nouvelles connaissances sur plusieurs des aspects majeurs de l’écologie en mer d’individus inexpérimentés cherchant leur nourriture seuls dans un environnement hautement imprévisible. Nous apprenons ici comment de l’instinct et de l’expérience découlent des stratégies de vie juvéniles qui permettent aux oiseaux de survivre dans un environnement inconnu. / The juvenile stage of animals is often much of a mystery to scientists. Moreover, juvenile survival is known to be a strong determinant for the future of a population. Indeed, juvenile animals are known to face high mortality during the first months after independence, with survival rates improving with age. One ultimate hypothesis implies that juveniles have a lower survival rate than adults because of their lack of experience. Thus they are initially poor foragers and require a learning period (immaturity) to improve their efficiency before being able to bear breeding and its associated energetic costs. Proximal factors also influence juvenile survival, such as environmental fluctuations and competition. Studies on terrestrial animals have provided useful information thanks to the possibility of direct observation and, recently, bio-logging technologies. However, collecting data in the marine environment is more difficult, particularly when juveniles are concerned. Long-lived marine species such as seabirds have an extensive immature period extending from a few years up to more than ten years. The offspring of these species will usually leave their natal site and disperse at sea for several years before returning to breed on land, most of the time at their place of birth. This makes it difficult to obtain direct observations, and so documenting their first journey at sea to learn more about their behavioural and foraging ecology is a challenge. In this context, this PhD aims to unravel at least part of the mystery of juvenile seabirds’ early life by investigating the first months at sea of newly fledged individuals from several long-lived species of procellariiformes. Using state of the art advancements in biotelemetry, I was able to follow, at sea, by satellite a large set of juveniles from nine closely related species of albatross and petrel breeding in the French Southern Territories of the Southern Ocean : Crozet, Kerguelen and Amsterdam Islands. Some of these species had never been tracked before. Trajectories were analysed using various new statistical methods that allowed movement strategies, alongside foraging behaviour and spatial distributions, to be described, all in tight link with environmental conditions. The findings were discussed in the light of a comparison with adults of the same species. Using this huge dataset I first examined the dispersal strategies of young birds that had left their nest and were totally independent from their parents. I showed that the strategies, as well as the amount of innate information controlling them are highly variable depending on species. Their movements take them in various habitats following or not the parental strategies. The amount of variability in juvenile strategies is linked to potential plasticity when facing environmental changes. These parameters are related to the history life trait of species, and might affect demography and population dynamics. In addition, by analysing juvenile wandering albatross tracks I showed that although they quickly learn the basics of flight and foraging optimization required to survive at sea, behavioural differences with adults persist in time, suggesting that non-observable behaviours need a longer period of learning and memorisation. Finally, whatever the strategy adopted, it seems to be driven in part by intraspecific competition since juveniles mitigate competition with older birds by segregating spatially. This last point highlights the crucial need of acknowledging age-related distribution when making management decisions to protect seabird populations. This work provides new insights about several major aspects of the at-sea ecology of naïve individuals foraging alone in a highly unpredictable environment. We learn here how instinct followed by experience shape specific early life strategies that allow young birds to deal with environmental conditions and interspecific competition so as to be able to survive.

Durant les dernières décennies, la Péninsule Antarctique a été identifiée comme étant la région où le réchauffement récent est le plus marqué dans l’Hémisphère Sud. Cependant, au-delà de la période instrumentale, la variabilité climatique Holocène de cette partie du globe est en grande partie inconnue. Cette absence de données limite notre capacité à évaluer les l’amplitude des changements actuels dans le contexte de la variabilité historique ainsi que les mécanismes de forçage sous-jacents. Nous avons ainsi ciblé nos analyses sur des enregistrements sédimentaires prélevés à l’Est et à l’Ouest de la Péninsule Antarctique, avec pour objectif d’étendre les connaissances spatiales et temporelles des conditions de l’océan de surfaces dans ce secteur de l’Antarctique au cours du dernier siècle, du dernier millénaire ainsi que durant l’Holocène. La méthodologie de cette thèse est basée sur une comparaison multi-proxies qui inclut, comme outils principaux, les assemblages des diatomées et les biomarqueurs spécifiques de diatomées (HBIs). Nous avons pu ainsi documenter la réponse régionale environnementale aux variations climatiques à différentes échelles de temps, et définir les mécanismes forçant sur la variabilité des conditions d’océan de surface ainsi que la formation du couvert de banquise en Péninsule Antarctique. La comparaison de nos enregistrements avec des données issues des carottes de glace, a permis de mettre en évidence le rôle important des changements d’intensité des cellules atmosphériques sur la dynamique de la circulation océanique, la durée du cycle saisonnier de banquise et la productivité siliceuse. / The Antarctic Peninsula has been identified during the last decades as the region from the Southern Hemisphere which is the most affected by the recent warming. However, beyond the instrumental period, the Holocene climate variability of this area is largely unknown, limiting our ability to evaluate the current changes within the context of historical variability and underpin the underlying forcing mechanisms. We focused our analysis on sedimentary sequences from the Eastern and Western side of the Antarctic Peninsula, in order to expand the spatial and temporal knowledge of sea-surface conditions over the last century, the last millennium and throughout the Holocene in this Antarctic area. The inferences are based on a multi-proxy comparison mainly using diatom assemblages and diatom specific biomarkers (HBIs). We documented the regional environmental response to climate changes at different time scales and described the forcing mechanisms on the sea-surface conditions and sea ice cover variability in Antarctic Peninsula. Comparing our results with ice core data allowed us to highlight the large impact of atmospheric forcings on the oceanic circulation, the seasonal sea ice dynamics and the siliceous productivity.

Cette étude vise à montrer de quelles manières les récits de Francisco Coloane contribuent à la définition d’une identité régionale australe à travers la représentation d’un espace naturel exceptionnel et la peinture de sociétés humaines marginales dont le mode d’existence est déterminé par leur environnement. L’écriture portant cette représentation témoigne d’une volonté de lever le voile sur une réalité méconnue, isolée et fantasmée, de saisir l’essence du monde austral. L’espace exploré s'écrit d'abord à travers l’expérience personnelle de son auteur en Patagonie où il a découvert des hommes, mais surtout des lieux et une nature à part qui seront au fondement d’un univers poétique unique. En accord avec la nature du lieu où les récits sont ancrés, Coloane écrit l’aventure. Une lecture approfondie de ses romans révèle que celle-ci s’y confond avec l’apprentissage de soi : les héros australs sont confrontés à une quête identitaire dont le sens est également collectif dans la mesure où leur trajectoire romanesque est représentative du destin d’une communauté. Dans le même temps, au sein de l’espace marin, la littérature de Coloane prend une dimension universelle car l’aventure en mer, en imposant à l’homme une confrontation permanente avec la mort, devient l’occasion de questionnements métaphysiques. Les enjeux de l’aventure ne sont pas seulement ontologiques : les récits proposent une aventure intellectuelle pleinement ancrée dans le contexte physique et culturel australs, guidée par des narrateurs géographe, naturaliste et ethnologue, autant de figures de savants et d’enquêteurs sur le monde austral. Les textes se révèlent les médiums d’un vaste savoir sur la région australe, dont ils réalisent la transmission. Ils participent ainsi de la saisie d’un monde qui reste toutefois essentiellement mystérieux. Enfin, le souci de vérité qui sous-tend l’écriture de Coloane doit s’entendre aussi comme un désir de justice : ses textes s’attachent à rendre visibles les ouvriers oubliés de l’histoire officielle ainsi que les habitants originels du Grand Sud, les Indiens australs, décimés par les promoteurs de l’exploitation industrielle de la région. Dans cette double perspective heuristique et critique, Coloane dévoile une réalité tragique longtemps occultée par le voile d'une utopie qui a fait des confins chiliens une terre avant tout romantique. Pourtant, tout en se dégageant de ce mythe, Coloane pense la survie de l'identité australe dans la pérennité de liens intimes entre l'homme et son milieu. / This study aims to show how the narratives of Francisco Coloane contribute to the definition of a regional Austral identity through the representation of exceptional natural spaces and the description of maginalized human societies whose way of existence is determined by its natural milieu. Coloane’s writing testifies to a desire to lift the veil on an unknown, isolated and fantasized reality and to understand the essence of the Austral world. The space explored in Coloane’s stories and novels is first of all that of the author’s personal experiences in Patagonia, where he discovered men, but above all places, an otherworldly nature that would become the foundation of a unique poetic universe. In keeping with the settings of his narratives, Coloane’s novels are adventures. Close reading reveals, however, that adventure isalways confounded here with the quest for self-knowledge : Coloane’s Austral heroes are engaged in a pursuit for identity whose meaning is also collective, to the extent that their novelistic trajectory is representative of the destiny of a community. At the same time, maritime space, Coloane’s work takes on a universal dimension, for adventure at sea, imposing on man a permanent confrontation with death, becomes the occasion for metaphysical examinations. The stakes of this adventure are not only ontological: Coloane’s work is an intellectual adventure fully anchored in the physical and cultural context of Chile’s southern territories, navigated by erudite, investigative narrators—geographers, naturalists and ethnologists of the Austral world. Coloane’s texts are vehicules for the transmission of an encyclopedic range of knowledge about Chile’s southernmost regions. They participate in the understanding of a world that remains nevertheless essentially mysterious. Finally, the concern for truth which underlies Coloane’s writing must also be understood as a desire for justice : his texts make visible the workers forgotten by official history as well as the indigeneous inhabitants of the extreme southern territories, decimated by the promoters of industrial exploitation in the region. From this heuristic and critical perspective, Coloane unveils a tragic reality long obscured by the veil of a utopia that transformed Chile’s outermost regions into the stuff of romantic legend. Abandoning such myths, Coloane nevertheless imagines the survival of the Austral identity in the permanence of intimate connections between man and his milieu.

Antarctic ice shelves control the ice flux from the continent to the ocean. As such, they play a major role in the stability of the ice sheet and its potential contribution to sea level rise, especially in the context of global change. Below some of these ice shelves, marine ice can be found which is a product of the Deep Thermohaline Circulation. Due to its specific genetic process, marine ice has intrinsic physical (grain size, ice fabric, bubble content, ) and chemical (impurities, water stable isotopes) properties, that differ from those of 'meteoric ice' formed on the continent through snow metamorphism or 'sea ice' resulting from sea water freezing at the ocean-atmosphere surface. Until now however, the effect of these specific properties on marine ice rheology is still very poorly understood.<p><p>The principal objective being to include realistic mechanical parameters for marine ice in ice shelf flow models, uniaxial compression experiments have been performed on various types of marine ice samples. Technical developments are an important component of this thesis has they were necessary to equip the laboratory with the appropriate tools (pneumatic rig, automatic ice fabric data handling).<p><p>Results from experimental compression on isotropic marine ice show that it represents the higher boundary for meteoric ice viscosity throughout the whole temperature range, thereby validating Cuffey and Paterson's relationship with an enhancement factor equals to 1.<p><p>Marine ice is however often quite anisotropic, showing elongated crystals and wide single maximum fabric, that should impact its mechanical properties. Experiments on pre-oriented marine ice samples have therefore been carried out combining the study of epsilon_{oct} vs. tau_{oct} with a thorough analysis of microstructural data 'before' and 'after' the experiment. <p><p>Depending on the orientation of the sample in the applied stress field and on the intensity of the latter, anisotropic marine ice can be harder or softer than its isotropic counterpart, with n=4 often observed in Glen's flow law. Associating the experimental geometrical settings to potential natural equivalent, results suggest that anisotropic marine ice would strengthen ice shelf flow in most areas (for a same given temperature), apart from suturing areas between individual ice streams as they merge to form the ice shelf, where it could become weaker than meteoric ice in certain circumstances.<p><p>Finally, preliminary sensitivity studies, using a simple ice shelf model with our experimental parameters of Glen's flow law have allowed us to discuss the potential impact of rift location, rift size and thermal regime in the ice shelf behavior. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Trabalhos prévios mostram que a variabilidade do gelo marinho antártico em diversas escalas temporais está intimamente relacionada a mecanismos de teleconexões trópicos-extratrópicos. Com base nesta hipótese, este trabalho pretende estabelecer a resposta da passagem dos trens de ondas em latitudes médias, associados a fenômenos de escala intrasazonal (20-100 dias) como a Oscilação de Madden-Julian (Madden-Julian Oscillation ou MJO), nas camadas superiores do Oceano Austral (OA) e impactos no gelo marinho antártico. O período investigado neste estudo é 19892007, com ênfase no inverno e sobre o mar de Ross, localizado no setor Pacífico austral (região diretamente afetada pela passagem dos trens de ondas de latitudes médias). Composições com defasagens (lag composites) de anomalias intrasazonais da tensão de cisalhamento do vento (zonal e meridional) mostram que correntes oceânicas são geradas em resposta a essa forçante atmosférica sobre o oceano no setor Pacífico austral. O transporte zonal e meridional de massa na camada de Ekman oceânica indica que divergência de massa nessa camada precede os eventos extremos intrasazonais de retração do gelo marinho em Ross (EIR). Em contraste, convergência precede períodos de eventos extremos intrasazonais de expansão do gelo marinho em Ross (EIE). A divergência (convergência) de massa na camada de Ekman associada com anomalias intrasazonais do bombeamento de Ekman resulta em ressurgência (subsidência) que precede a ocorrência de EIR (EIE). Alguns trabalhos mostram que águas intermediárias antárticas, que são relativamente mais quentes no inverno em relação às águas superficiais que estão próximas ao ponto de congelamento (ou congeladas), são dirigidas para a superfície do oceano pelo bombeamento de Ekman e ocasionam o derretimento do gelo marinho. Anomalias do transporte meridional de calor na camada de Ekman oceânica mostram que durante os EIR (EIE), calor é transportado para dentro (fora) do mar de Ross entre 15 e 8 dias (12 e 8 dias) precedentes aos EIR (EIE). Anomalias intrasazonais do fluxo de calor na interface ar-mar mostram que precedendo o dia de observação dos EIR (EIE) o fluxo de calor é direcionado da atmosfera para o oceano (do oceano para a atmosfera), sendo essa configuração associada a um ganho (perda) de calor no oceano superior em Ross. Em todas as composições, observa-se a mudança de fase das anomalias nos dias posteriores (lags positivos) ao dia dos EIG e são consistentes com a propagação do modo conhecido como Pacific-South-American (PSA), identificado nesse trabalho por meio de anomalias intrasazonais da altura geopotencial em 200 hPa. Além disso, uma diferença notada em alguns casos nas lag-composities é que em períodos de MJO ativa, as anomalias parecem estar mais deslocadas para o sul do que em períodos de MJO inativa. Em períodos de MJO inativa foram observados 15 (13) eventos de EIR (EIE), enquanto que, em períodos de MJO ativa observou-se 25 (24) eventos de EIR (EIE). Observa-se ainda que há uma maior quantidade de ciclones quando a MJO está presente. Por exemplo, o número de ciclones com duração a partir de 12 horas para períodos sem MJO foi igual a 146 para os EIR e 130 para os EIE. Já o número de ciclones para períodos com MJO foi igual a 311 para os EIR e 278 para os EIE. Com isso, observa-se claramente o papel da MJO na circulação de latitudes média e possíveis associações com o gelo marinho, pois é sabido que a atividade ciclônica está relacionada à advecção de massas de ar sobre o gelo marinho, além da advecção do próprio gelo marinho. Para investigar em detalhes a interação oceano-atmosfera-gelo marinho foram examinados casos persistentes de EIR e EIE. Os casos mais persistentes de EIR (EIE) tiveram durações de 34 e 30 (26 e 25) dias, sendo esses os casos analisados. Mostra-se que as anomalias intrasazonais da circulação atmosférica em baixos níveis (em 850 hPa) estão associadas a advecções quentes (frias) na proporção de aproximadamente 0,5 1 (0,1 1) m.s-1 em períodos precedentes aos EIR (EIE). No geral, anomalias em latitudes médias da circulação atmosférica ciclônicas (anti-ciclônicas) e divergência (convergência) das correntes oceânicas superficiais aparecem relacionadas à ressurgência (subsidência) da ordem de 0,1 0,3 m2.s-1 em algumas pêntadas anteriores a pêntada que corresponde ao início dos supercasos de EIR (EIE). Os padrões mudam de fase com o tempo, o que sugere a propagação de um padrão de onda em escala intrasazonal. Estas anomalias mostram-se abrangendo dimensões espaciais que compreendem grande parte do setor Pacífico austral, incluindo o mar de Ross. Impactos associados a estas anomalias podem ser verificados diretamente no mar de Ross através das análises da concentração do gelo marinho em Ross. Anomalias intrasazonais negativas (positivas) da concentração do gelo marinho predominam sobre o campo do gelo marinho do mar de Ross nas primeiras pêntadas a partir daquela que indica o início dos casos persistentes de EIR (EIE). Durante os períodos de EIR, as anomalias intrasazonais negativas da concentração do gelo mostram-se da ordem de aproximadamente 5% a 10% no interior do mar de Ross e entre 15% a 30% nas bordas do gelo marinho de Ross. Já durante os períodos de EIE, as anomalias intrasazonais positivas da concentração do gelo marinho em Ross mostram-se da ordem de 10% a 30% nas bordas do gelo marinho do mar de Ross. Esse resultado mostra que a resposta do gelo marinho aos padrões atmosféricos e oceânicos em escala intrasazonal possui uma defasagem entre 5 e 1 pêntada(s). No geral, este trabalho cumpriu o objetivo de verificar as respostas do oceano às anomalias da circulação atmosférica e impactos associados no gelo marinho, em escala intrasazonal. / Previous works show that antarctic sea ice variability on several time-scales is close related to tropics-extratropics teleconections mechanisms. Based on this hyphotesis, this work intend to verify the responses in oceanic upper layers of Austral Ocean on intraseasonal time-scale (20-100 days) phenomenom and impacts on sea ice due to anomalous atmospheric circulation associated to the Madden-Julian Oscillation (MJO). The period analysed in this study is from 1989 to 2007, with emphasis on winter season and on Ross Sea (located at austral Pacific sector). Lag composities of zonal and meridional intraseasonal wind stress anomalies show that oceanic currents are generated as a response of these atmospheric forcings on austral Pacific sector. Zonal and meridional mass transport on oceanic Ekman layer, which are perpendicular and to the left of wind stress at Southern Hemisphere (SH), indicate that Ekman mass divergence precedes intraseasonal Ross sea ice extreme retraction (EIR). In contrast, convergence precedes the periods of extreme intraseasonal Ross sea ice expantion (EIE). Divergence (convergence) on oceanic Ekman layer associated to intraseasonal Ekman pumping anomalies results in upwelling (downwelling) wich precedes the occurrence of EIR (EIE). Some works have already shown that intermediate antarctic waters, wich are relatively warmer in the wintertime when compared to superficial waters that are next to the freezing point (or freezed), are headed to ocean surface due to Ekman pumping, generating sea ice melt. Intraseasonal anomalies of sea-air heat flux show that days before EIR (EIE) occurrences, the flux is headed from atmosphere to the ocean (from ocean to the atmosphere), which configuration is associated to the earn (loss) of heat at Ross upper ocean. In all compositions, the change of anomalies phase on the days before EI occurrence (positive lags) is clearly noticed and is consistent to the propagations of the mode known as Pacific South American (PSA), revealed in intraseasonal anomalies of geopotencial height at 200 hPa. Furthermore, in some cases (as in the case of Ekman pumping and Sverdrup transport) the anomalies seem to be deplaced southward in active MJO periods than in inactive MJO periods. In inactive MJO periods were observed 15 (13) EIR (EIE) events, while in active MJO periods were observed 25 (24) EIR (EIE) events. Furthermore, the number of cyclones during EIR periods was bigger than during EIE periods. In addiction, more cyclones were observed when MJO is active. For example, the number of cyclones with duration of 6 (12) hours without MJO was equal to 174 (146) during EIR events and 169 (130) during EIE events. However, the number of cyclones with active MJO was equal to 393 (311) in EIR events and 364 (278) in EIE events. In order to investigate in details the interaction between ocean-atmosphere-sea ice, it was examinated persistents cases of EIR and EIE events. The cases more persistents of EIR (EIE) events had durations of 34 and 30 (26 and 25) days, which were the analised cases. It was observed that intraseasonal anomalies of atmospheric circulation at lower levels (in 850 hPa) and intraseasonal anomalies of superficial ocean currents were associates to hot (cold) advection during periods before EIR (EIR) events. In general, the medium latitude cyclonic (anticyclonic) anomalies of atmospheric circulation and divergence (convergence) of superficial ocean currents seem to be linked to upwelling (downwelling) in some pentads before the pentad which is correspondent to the beggining of EIR (EIE) supercases. The patterns observed change their phases along the time, suggesting the propagation of extratropical intraseasonal wave train pattern. Negatives (positives) intraseasonal anomalies of sea ice concentration were observed above Ross Sea in the first pentads after the beggining of EIR (EIE) persistents cases. This result shows that sea ice response to atmospheric and to oceanic patterns on intraseasonal time-scales has a lag between 5 and 1 pentad(s). In general, this work contributed to better understand the oceanic responses due to anomalies in atmospheric circulation and related impacts on sea ice, on intraseasonal time-scale.

Les tendances climatiques récentes montrent un réchauffement et un adoucissement des couches de surface dans la région du courant circumpolaire antarctique (ACC).Sur la même période, les vents d'ouest pilotant la circulation de l'océan Austral ont significativement augmentés. Cette augmentation est en partie liée à l'intensification du mode annulaire austral (SAM), principal mode de variabilité atmosphérique au sud de 20°S. Dans cette thèse, on s'intéresse à comprendre les effets de la tendance positive du SAM sur les propriétés des masses d'eau formées dans la région de l'ACC.A cette fin, on met en place une stratégie de simulations régionales couplées océan-glace de mer et forcées par une série de scénarios atmosphériques perturbés. Les scénarios atmosphériques sont construits à partir de réanalyses atmosphériques afin de décrire les différentes composantes (dynamiques et thermodynamiques) des changements liés au SAM.En réponse à l'intensification du SAM, les simulations montrent une forte salinisation de la couche de mélange océanique ainsi que des eaux modales (SAMW) et intermédiaires (AAIW).L'essentiel de ces changements peut être attribué aux composantes dynamiques du SAM. Dans les régions saisonnières englacées, les composantes thermodynamiques du SAM peuvent jouer un rôle important (en particulier en mer d'Amundsen et en mer de Weddell). Les simulations montrent également le rôle clef joué par la glacede mer dans la médiation des changements atmosphériques vers l'océan intérieur. Ces résultats de simulations suggèrent que le SAM ne serait pas le seul pilote des tendances climatiques récentes dans l'océan Austral. / Recent climate trends show a warming and freshening of the surface layers in the region of the Antarctic Circumpolar Current (ACC). Over the same period, the westerlies driving the circulation of the Southern Ocean have significantly increased. This increase is partly due to the intensification of the Southern Annular Mode (SAM), the main mode of atmospheric variability south of 20°S. In this thesis, we are interested in understanding the effects of the positive trend of the SAM onto the properties of water masses formed in the region of the ACC. To do so, we implement a strategy of regional coupled ocean-sea ice simulations forced by a series of atmospheric disturbance scenarios.These scenarios are constructed from atmospheric reanalyses in order to describe the various components (dynamic and thermodynamic) of the changes related to the SAM. In response to the increase of the SAM, the simulations show a significant salinification of the ocean mixed layer and of the mode water (SAMW) and intermediate water (AAIW).Most of these changes can be attributed to the dynamic components of the SAM. In Seasonal Ice Zone, the thermodynamic components of the SAM can play an important part (especially in Amundsen Sea and Weddell Sea). The simulations also show the key role played by sea ice in mediating atmospheric changes toward the interior ocean.These simulation results suggest that SAM is not the only driver of recent climate trends in the Southern Ocean.