Doctor en Ciencias, Mención Geología / Modificaciones del relieve provocados por procesos geológicos de gran escala como el alzamiento de cordilleras tiene importantes efectos en las condiciones climáticas y generan cambios significativos del paisaje. De esta forma, variaciones en las condiciones de temperatura y precipitación de una región afectan directamente la distribución, diversidad y composición de la vegetación. En la actualidad la dirección de flujo de los ríos en el sur de Sudamérica es principalmente hacia el oriente, sin embargo, aún no es claro cuál fue la dirección de las corrientes y las zonas de proveniencia en el pasado. Cambios en las direcciones de paleocorrientes ocurridos durante el Cenozoico en la Cuenca de Magallanes, junto con cambios de ambientes, pasando de marinos a transicionales y finalmente a ambientes continentales, procesos que fueron identificados en el sector de Sierra Baguales, al norte del Parque Nacional Torres del Paine, podrían vincularse con el levantamiento de los Andes Patagónicos, proceso que a su vez podría asociarse a cambios paleoclimáticos y paleoecológicos que habrían sido provocados por el efecto de sombra de lluvia y apertura del paso Drake durante el Oligoceno, cambios paleogeográficos que a su vez coinciden con modificaciones de las zonas de aporte de sedimentos a la Cuenca de Magallanes y la posición relativa de Península Antártica. El presente estudio evalúa cual fue el efecto de los procesos tectónicos como el levantamiento de los Andes Patagónicos, apertura del Paso Drake y cambios en las zonas de proveniencia. Se discute el vínculo entre la evolución de la Cuenca de Magallanes y la posición de la Península Antártica. Estos procesos fueron evaluados a partir de la evolución espacio-temporal de las paleocorrientes y el establecimiento de las zonas que aportaron detritos a la Cuenca durante el Cenozoico en Sierra Baguales, adicionalmente, junto con la evolución tectónica y sedimentológica del sector, se analiza la respuesta de la vegetación en términos de diversidad y composición, comportamientos analizados bajo un contexto de cambio climático global durante el Cenozoico donde especialmente se discute la respuesta de la vegetación frente a procesos de enfriamiento como el ocurrido durante el Oligoceno.

This work is an archaeological biography of three skeletons brought to Sweden from Tierra del Fuego in the late 1800s by scientist Otto Nordenskjöld and his Swedish expedition to the Magellan countries. These belonged to Selknam men killed by European farmers. In Sweden they were used in studies of comparative anatomy and as teaching and research material. They reflect the European colonial worldview of the 19th- and early 20th centuries, as well as a part of the colonial history of Patagonia and Tierra del Fuego. / Este trabajo es una biografía arqueológica sobre tres esqueletos traídos a Suecia desde Tierra del Fuego a fines de 1800, por el científico Otto Nordenskjöld y su expedición sueca a los países magallánicos. Estos pertenecían a hombres selknam, asesinados por estancieros europeos. En Suecia fueron utilizados en estudios de anatomía comparada y como material de enseñanza e investigación. Son un reflejo de la cosmovisión colonial europea de los siglos XIX y principios del XX, así como una parte de la historia colonial de Patagonia y Tierra del Fuego.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / O Oceano Austral é a região oceânica de maior extensão em que os macronutrientes necessários à produção primária permanecem em níveis elevados por todo ano. Essa condição é conhecida como High Nutrient Low Clorophyll (HNLC) e é determinada, em grande parte, pela relativa escassez de micronutrientes, particularmente o ferro. Diversos experimentos comprovaram que a entrada de ferro neste sistema intensifica a produção biológica, aumentando a fixação do carbono e, eventualmente, sua exportação para águas profundas. Este fenômeno recebeu muita atenção nos últimos 20 anos devido a sua possível influencia no clima, via ciclo do carbono. A relação inversa entre concentração de CO2 na atmosfera e o fluxo de poeira mineral observados em registros glaciais da Antártica Central sugere que a deposição atmosférica pode ser uma importante via para o aporte de micronutrientes. Porém, a contribuição da deposição de poeira mineral para a produção primária nesta região permanece para ser demonstrada e seu possível papel no sistema climático ainda não é conclusivo. No caso do setor Atlântico do Oceano Austral, que recebe influência da Patagônia, os baixos fluxos modernos de poeira mineral e a baixa solubilidade do ferro associado à estrutura dos alumíniossilicato levam muitos autores a postular que fontes oceânicas de micronutrientes sejam mais determinantes. Faltam, no entanto, evidências experimentais. Neste trabalho, abordamos o estudo da fertilização do setor Atlântico do Oceano Austral pela poeira da Patagônia utilizando duas ferramentas: (1) o sensoriamento remoto orbital de aerossóis minerais e clorofila-a em escala interanual; e (2) um experimento de fertilização, com poeira da Patagônia, realizado na Passagem de Drake, considerando fluxos estimados para a era moderna e para o último glacial. Após doze dias de bioensaio, os tratamentos de adição de poeira mostraram a elevação da clorofila-a e da abundância de células em níveis acima dos controles. Níveis intermediários e maiores de adição não diferiram entre si na intensidade de resposta biológica, separando-se apenas da menor adição. Esses resultados indicam que a poeira da Patagônia, mesmo nos fluxos atuais, é capaz de prover os micronutrientes escassos na coluna dágua, com potencial para deflagrar aumentos significativos de biomassa. Através da análise por sensoriamento remoto, identificamos uma região de alta correlação entre poeira e clorofila-a, que está localizada entre a Frente Subtropical e a Frente Polar, se estendendo da Argentina ao sul da África. Esta região difere das águas ao sul da Frente Polar pela menor profundidade da camada de mistura, menor concentração de silicatos, baixa biomassa de diatomáceas e, estima-se, maior estresse fisiológico devido à escassez de ferro e menor aporte oceânico deste nutriente. Em conjunto, essas características parecem criar condições que tornam a resposta biológica mais sensível à deposição de poeira mineral. Estes resultados lançam nova luz sobre o controle atual da produção primária na região e sobre a hipótese da regulação climática pelo fitoplâncton no Oceano Austral, mediado pela deposição de poeira da Patagônia. / The Southern Ocean is the larger ocean region where the macronutrients needed for primary production remain in high levels through the year. This condition is known as High Nutrient Low Chlorophyll (HNLC) and is conditioned, largely, by the relative shortage of micronutrients, particularly iron. Several experiments proved that the supply of iron to this system enhances biological production, increasing carbon fixation and, eventually, its exportation to deep waters. This phenomenon received much attention in the last 20 years due to its possible influence in the climate, through carbon cycle. The inverse relationship between the atmospheric CO2 concentration and the mineral dust flux observed on the Central Antarctic glacial records suggest that atmospheric deposition may be an important source for the supply of micronutrients. However, the contribution of mineral dust deposition for the primary production in this region remains to be demonstrated and its possible hole in the climate system its not yet conclusive. In the case of Atlantic Southern Ocean, thats influenced by Patagonia, the low modern flows of mineral dust and the low iron solubility associated with aluminum-silicate structure led many authors to state that oceanic sources of micronutrients are more determinants. However, experimental evidence are lacking. In the present work, we approach the study of fertilization of Atlantic Southern Ocean by Patagonian dust employing two different tools: (1) orbital remote sensing of mineral aerosols and chlorophyll-a on inter-annual scale; and (2) a fertilization experiment with Patagonian dust, carried through in Drake Passage, considering estimated flux for the modern era and for the last glacial. After twelve days of bioassay, the dust addition treatments showed increase on chlorophyll-a and cell abundance beyond controls levels. Intermediary and higher levels of addition didnt differ between each other regarding the intensity of biological response, separating only of the lower addition treatment. These results indicate that even modern Patagonia dust flux is capable of providing micronutrients that are scarce in the water column, with potential to deflagrate a bloom. Through remote sensing analysis we have identified a region with high correlation between dust and chlorophyll-a, thats located between the Subtropical Front and the Polar Front, extending from Argentina to south of Africa. This region differs from waters south of the Polar Front by means of a deeper mixed layer, lower silicate concentrations, low diatom biomass and, is estimated, greater iron physiological stress and lower iron oceanic supply. Together, these properties seem to create conditions to which biological response would be more sensible to dust deposition. These results cast new light over controls on modern primary production in the region and over the phytoplankton climatic regulation in the Southern Ocean, mediated by Patagonian dust deposition.

The southern Patagonian Andes record the Late Cretaceous closure and inversion of the Late Jurassic – Early Cretaceous Rocas Verdes marginal basin, subsequent development of the Patagonian retroarc fold-thrust belt and the Neogene to present tectonic superposition of a left-lateral strike-slip plate margin defined by the Magallanes- Fagnano fault zone. In this dissertation, I present new geologic maps, cross sections and detailed macro- and microscopic structural analyses that describe the geometry and kinematic evolution of the fold-thrust belt and superposed strike-slip deformation over ~200 km along-strike between 53° and 55° S latitude. Results are discussed in the context of the regional tectonic development of the southernmost Andes and are relevant to the understanding of important tectonic processes including the development of a retroarc fold-thrust belt, the formation of a basal décollement below and toward the hinterland of a fold-thrust belt and the spatial distribution of deformation along a strike-slip plate margin. New maps and balanced cross-sections of the Patagonian fold-thrust belt show that it developed during two main phases of Late Cretaceous to Paleogene shortening that were partly controlled by the antecedent geology and mechanical stratigraphy of the Rocas Verdes basin. During the Late Cretaceous, a thin-skinned thrust belt developed above a décollement that formed first in relatively weak shale deposits of the Rocas Verdes basin and later deepened to <1 km below the basement-cover contact. Ramps that cut mechanically rigid volcanic rocks of the marginal basin link the two décollements. Basement-involved reverse faults that cut the early décollements and probably reactivate Jurassic normal faults reflect Paleogene shortening. Shortening estimates increase northwest to southeast from 26 to 37% over 100 km along-strike and are consistent with regional models of the fold-thrust belt. Structural data, kinematic analyses, and microstructural observations from the lower décollement show that it is defined by transposition of several generations of northeast-vergent noncylindrical folds, shear bands, and a quartz stretching lineation that are kinematically compatible with first-generation structures of the fold-thrust belt. Quartz microstructural data from the décollement are consistent with deformation temperatures that decrease from ~500-650° C to ~400-550° C over ~75 km in the transport direction, indicating that the décollement dipped shallowly (~6°) toward the hinterland. The décollement decoupled the underthrust continental margin from the fold- thrust belt and exemplifies the kinematic relationship between shortening that occurs coevally in a retroarc fold thrust-belt and its polydeformed metamorphic ‘basement’. Fault kinematic data and crosscutting relationships show kinematic and temporal relationships between populations of thrust, strike-slip and normal faults that occur in the study area. Thrust faults form an internally compatible population that shows subhorizontal northeast-trending shortening of the fold-thrust belt and is kinematically distinct from populations of normal and strike-slip faults. Both strike-slip and normal faults crosscut the fold-thrust belt, are localized near segments of the Magallanes- Fagnano fault zone, have mutually compatible kinematic axes and are interpreted to be coeval. Strike-slip faults form Riedel and P-shear geometries that are compatible with left-lateral slip on the Magallanes-Fagnano fault-zone. Strike-slip and normal faults occur in a releasing step-over between two overlapping left-lateral, left-stepping segments of the Magallanes fault zone and record a tectonic event defined by sinistral transtension that probably reflects changing plate dynamics associated with the opening of the Drake Passage during the Early Miocene. / text

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

La présente recherche souligne l'importance de la pêche chez les chasseurs cueilleurs marins de la région centrale du détroit de Magellan et des mers adjacentes. L'approche méthodologique prend en compte l'analyse ichthyoarchéologique de 13 sites archéologiques couvrant une chronologie de 6000 à 1000 ans BP. La méthode de la sclérochronologie est appliquée aux vertèbres de l'espèce la plus importante (Salilota aust alis) afin d'évaluer la saisonnalité des activités de pêche. Les techniques de pêche sont abordées à partir des éléments de technologie découverts dans les gisements étudiés (poids lithiques, pointes en os, murets de pêcherie) et de l'information ethnographique. Les résultats permettent de discuter et de réévaluer le rôle de la pêche par rapport à la chasse aux mammifères marins, généralement estimée (avec les mollusques) comme l'axe principal de subsistance de ces sociétés nomades. Des changements radicaux sont observés dans le modèle d'exploitation des poissons à travers le temps. On observe à l'époque ancienne et moyenne (de 6000 à 2000 ans BP) une grande spécialisation dans des espèces démersales exploitées à différents moments de l'année, et l'emploi de technologies spécialisées standardisées. Au cours des derniers 2000 ans et jusqu'à la période ethnographique, la pêche est concentrée sur les bords de côte ; son rôle dans la subsistance est variable et on observe des stratégies opportunistes permises par l'usage de techniques de pêche variées. Le modèle d'exploitation observé tout au long de la séquence chronologique est différent de celui qui avait été suggéré par D. Zangrando pour les nomades marins du canal Beagle, où est observée une intensification progressive de la pêche à travers le temps. Finalement on remarque le haut niveau de spécialisation de la pêche chez les premiers indiens canoeros qui ont peuplé la région de Magellan, il y a 6000 ans, ce qui permet de discuter du degré d'adaptation de ces populations aux milieux marins. Cette observation renforce l'hypothèse, de plus en plus documentée, d'un peuplement maritime venu du nord, le long de la côte pacifique. / This research highlights the importance of fishing in marine hunter-gatherers of the central region of the Magellan Strait and adjacent seas. The methodological approach takes into account the ichthyoarchaeological analysis of 13 archaeological sites covering a chronology from 6000 to 1000 years BP. The Sclerochronology method is applied to the vertebrae of the most important species (Salilota australis) to estimate the seasonality of fishing activities. Fishing techniques are discussed from technology elements discovered in the studied deposits (weight lithic, bone points, fishing weirs) and ethnographic information. The results allow to discuss and reassess the role of fisheries in respect to the hunting of marine mammals, generally estimated to be (along with shellfish) the main source of subsistence nomadic societies. Radical changes are observed on fishing strategies over time. We observe in the Early and Middle Periods (6000 to 2000 years BP) a specialization in demersals species exploited at different moments of the year, and the use of standardized and specialized technologies. ln the last 2000 years until the ethnographic period, fishing is concentrated on the seashore; the role in subsistence is variable and opportunistic strategies enabled by the use of various fishing technics can be observed. The fishing strategies observed throughout the chronological sequence is different from the one suggested by F. Zangrando for the marine nomads of the Beagle Channel, where a progressive intensification of fishing through time is detected. Finally this research emphasizes the high level of the fishing specialization of the first canoeros Indians who populated the region of Magallanes, 6000 years ago, which allows us to discuss the degree of adaptation of these populations to marine environments. This observation strengthens the hypothesis, increasingly documented, of the existence of a maritime population from the Northern regions, along the Pacific Coast.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / O Oceano Austral é a região oceânica de maior extensão em que os macronutrientes necessários à produção primária permanecem em níveis elevados por todo ano. Essa condição é conhecida como High Nutrient Low Clorophyll (HNLC) e é determinada, em grande parte, pela relativa escassez de micronutrientes, particularmente o ferro. Diversos experimentos comprovaram que a entrada de ferro neste sistema intensifica a produção biológica, aumentando a fixação do carbono e, eventualmente, sua exportação para águas profundas. Este fenômeno recebeu muita atenção nos últimos 20 anos devido a sua possível influencia no clima, via ciclo do carbono. A relação inversa entre concentração de CO2 na atmosfera e o fluxo de poeira mineral observados em registros glaciais da Antártica Central sugere que a deposição atmosférica pode ser uma importante via para o aporte de micronutrientes. Porém, a contribuição da deposição de poeira mineral para a produção primária nesta região permanece para ser demonstrada e seu possível papel no sistema climático ainda não é conclusivo. No caso do setor Atlântico do Oceano Austral, que recebe influência da Patagônia, os baixos fluxos modernos de poeira mineral e a baixa solubilidade do ferro associado à estrutura dos alumíniossilicato levam muitos autores a postular que fontes oceânicas de micronutrientes sejam mais determinantes. Faltam, no entanto, evidências experimentais. Neste trabalho, abordamos o estudo da fertilização do setor Atlântico do Oceano Austral pela poeira da Patagônia utilizando duas ferramentas: (1) o sensoriamento remoto orbital de aerossóis minerais e clorofila-a em escala interanual; e (2) um experimento de fertilização, com poeira da Patagônia, realizado na Passagem de Drake, considerando fluxos estimados para a era moderna e para o último glacial. Após doze dias de bioensaio, os tratamentos de adição de poeira mostraram a elevação da clorofila-a e da abundância de células em níveis acima dos controles. Níveis intermediários e maiores de adição não diferiram entre si na intensidade de resposta biológica, separando-se apenas da menor adição. Esses resultados indicam que a poeira da Patagônia, mesmo nos fluxos atuais, é capaz de prover os micronutrientes escassos na coluna dágua, com potencial para deflagrar aumentos significativos de biomassa. Através da análise por sensoriamento remoto, identificamos uma região de alta correlação entre poeira e clorofila-a, que está localizada entre a Frente Subtropical e a Frente Polar, se estendendo da Argentina ao sul da África. Esta região difere das águas ao sul da Frente Polar pela menor profundidade da camada de mistura, menor concentração de silicatos, baixa biomassa de diatomáceas e, estima-se, maior estresse fisiológico devido à escassez de ferro e menor aporte oceânico deste nutriente. Em conjunto, essas características parecem criar condições que tornam a resposta biológica mais sensível à deposição de poeira mineral. Estes resultados lançam nova luz sobre o controle atual da produção primária na região e sobre a hipótese da regulação climática pelo fitoplâncton no Oceano Austral, mediado pela deposição de poeira da Patagônia. / The Southern Ocean is the larger ocean region where the macronutrients needed for primary production remain in high levels through the year. This condition is known as High Nutrient Low Chlorophyll (HNLC) and is conditioned, largely, by the relative shortage of micronutrients, particularly iron. Several experiments proved that the supply of iron to this system enhances biological production, increasing carbon fixation and, eventually, its exportation to deep waters. This phenomenon received much attention in the last 20 years due to its possible influence in the climate, through carbon cycle. The inverse relationship between the atmospheric CO2 concentration and the mineral dust flux observed on the Central Antarctic glacial records suggest that atmospheric deposition may be an important source for the supply of micronutrients. However, the contribution of mineral dust deposition for the primary production in this region remains to be demonstrated and its possible hole in the climate system its not yet conclusive. In the case of Atlantic Southern Ocean, thats influenced by Patagonia, the low modern flows of mineral dust and the low iron solubility associated with aluminum-silicate structure led many authors to state that oceanic sources of micronutrients are more determinants. However, experimental evidence are lacking. In the present work, we approach the study of fertilization of Atlantic Southern Ocean by Patagonian dust employing two different tools: (1) orbital remote sensing of mineral aerosols and chlorophyll-a on inter-annual scale; and (2) a fertilization experiment with Patagonian dust, carried through in Drake Passage, considering estimated flux for the modern era and for the last glacial. After twelve days of bioassay, the dust addition treatments showed increase on chlorophyll-a and cell abundance beyond controls levels. Intermediary and higher levels of addition didnt differ between each other regarding the intensity of biological response, separating only of the lower addition treatment. These results indicate that even modern Patagonia dust flux is capable of providing micronutrients that are scarce in the water column, with potential to deflagrate a bloom. Through remote sensing analysis we have identified a region with high correlation between dust and chlorophyll-a, thats located between the Subtropical Front and the Polar Front, extending from Argentina to south of Africa. This region differs from waters south of the Polar Front by means of a deeper mixed layer, lower silicate concentrations, low diatom biomass and, is estimated, greater iron physiological stress and lower iron oceanic supply. Together, these properties seem to create conditions to which biological response would be more sensible to dust deposition. These results cast new light over controls on modern primary production in the region and over the phytoplankton climatic regulation in the Southern Ocean, mediated by Patagonian dust deposition.

Tese(mestrado) - Universidade Federal Do Rio Grande, Programa de Pós-graduação em Oceanografia Biológica, Instituto de Oceanografia, 2013. / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-11-18T12:52:36Z No. of bitstreams: 1 AMABILE.pdf: 5765676 bytes, checksum: a4926b187c0614bc4d913a29b23870ab (MD5) / Approved for entry into archive by Angelica Miranda (angelicacdm@gmail.com) on 2013-11-18T19:07:50Z (GMT) No. of bitstreams: 1 AMABILE.pdf: 5765676 bytes, checksum: a4926b187c0614bc4d913a29b23870ab (MD5) / Made available in DSpace on 2013-11-18T19:07:50Z (GMT). No. of bitstreams: 1 AMABILE.pdf: 5765676 bytes, checksum: a4926b187c0614bc4d913a29b23870ab (MD5) Previous issue date: 2013 / Imagens de satélite da cor do oceano detectam intensas florações do fitoplâncton durante primavera e verão ao longo da quebra de plataforma Argentina, mas são escassas as medidas ópticas in situ na região. O objetivo geral desta tese foi investigar a variabilidade das propriedades ópticas das florações do fitoplâncton na quebra de plataforma Argentina e arredores. Entre 2006 e 2009, seis cruzeiros foram conduzidos com diversas medidas biológicas e físicas, incluindo medicões bio-ópticas, dentre as quais algumas inéditas na região. As seguintes medidas foram consideradas: coeficientes spectrais de absorção da luz pelo material particulado, que inclui o fitoplâncton e detritos; coeficiente de atenuação da luz pelo material particulado a 660nm; irradiância descendente e radiância ascendente da luz com alta resolução espectral, a partir das quais se obtém os coeficientes da atenuação difusa e a reflectância do sensoriamento remoto in situ; reflectância do sensoriamento remoto medida por satélite; concentração de clorofila-a total e fracionada por classes de tamanho do fitoplâncton estimada pelo método fluorimétrico; concentrações de clorofila-a e pigmentos acessórios do fitoplâncton, obtidas por HPLC; abundância taxonômica relativa do fitoplâncton estimada por CHEMTAX; e fator de tamanho celular do fitoplâncton estimado pelos espectros de absorção da luz pelo fitoplâncton. Grande variabilidade foi observada nos coeficientes de absorção, atenuação (e espalhamento) e atenuação difusa da luz para uma dada concentração de clorofila-a e vice-versa. Grande parte dessa variabilidade pôde ser explicada por variações no tamanho celular do fitoplâncton e, portanto, ao efeito “pacote”. A variabilidade nos espectros de reflectância do sensoriamento remoto (propriedade óptica aparente) medidos in situ revelou o fitoplâncton como componente dominante nas propriedades ópticas das florações na região. Porém, a variabilidade nos coeficientes específicos (i.e., normalizados por clorofila-a) de absorção e espalhamento (propriedades ópticas inerentes), devido a variações no tamanho celular do fitoplâncton, influenciou o desempenho de modelos bio-ópticos para estimar concentração de clorofila-a por satélite. As principais situações de composição taxonômica do fitoplâncton que ocorrem durante as florações na região (dominância por diatomáceas, haptofíceas, e com contribuições destes grupos e de outros, sem dominância) foram refletidas de forma coerente nos comportamentos espectrais de absorção da luz pelo fitoplâncton, indicando o potencial em discriminar as assembleias das florações na região através de dados ópticos. Particularmente, a identificação de dominância de diatomáceas e haptofíceas, a partir de um comprimento de onda, e também pelo fator de tamanho celular do fitoplâncton, que pode ser estimado por satélite, indica o potencial em identificar a dominância de tais grupos taxonômicos por sensoriamento remoto na região. / Satellite images usually detect intense phytoplankton blooms during spring and summer along the Argentina shelf break. Because in situ optical measurements are scarce in the region, six cruises were conducted from 2006 to 2009 to measure several physical, biological, and optical properties. Some of the bio-optical properties were gathered for the first time in the region. The aim of this thesis was to characterize the optical properties of phytoplankton blooms along the Argentina shelf break e adjacent areas. For this purpose, the following measurements and data were considered: light absorption coefficients of particulate material that includes phytoplankton and detritus; light attenuation coefficient of particulate material at 660 nm; hyperspectral downwelling irradiance and upwelling radiance, from which one obtains the vertical attenuation coefficients for downwards irradiance and upwards radiance and in situ reflectance of remote sensing; total and size-fractionated chlorophyll-concentration, estimated by fluorimetric method; concentrations of chlorophyll-a and accessory pigments of phytoplankton obtained by HPLC; relative taxonomic abundance of phytoplankton estimated by CHEMTAX; a cell size parameter for phytoplankton estimated from the phytoplankton absorption spectra. Large variability was observed for absorption coefficients of phytoplankton, scattering of particles and the vertical attenuation coefficients for downwards irradiance for a given chlorophyll-a concentration. Such variability could be largely explained by variations in cell size of phytoplankton and therefore the "package" effect, as indicated by the cell size parameter. The characterization of the variability in the remote sensing reflectance (apparent optical property) measured in situ revealed phytoplankton as the dominant component on the optical properties of algal blooms in the region. Nevertheless, the variability in absorption and scattering coefficients (inherent optical properties) due to variations in cell size of phytoplankton was shown to impact the performance of bio-optical models that relies on band reflectance ratios of remote sensing to retrieve chlorophyll-a from satellite. The main taxonomic composition of the phytoplankton blooms (dominance of diatoms, haptophytes, and mixed contributions of these and others groups, but with no dominance) was consistently reflected on the spectral shape of light absorption of phytoplankton. Our results indicate a potential to discriminate phytoplankton assemblages in the region through optical data. Particularly, the identification of diatoms or haptophytes using one wavelength or through a phytoplankton cell size parameter, which can be estimated from satellite, has a potential of identifying the dominance of such taxonomic groups from remote sensing in the region.

Ce travail de thèse est centré sur l'analyse des compositions isotopiques de la glace (d18O et dD) de deux nouvelles carottes de glace longues provenant des régions subtropicale et tempérée des Andes. La première carotte, longue de 42m, a été extraite en 2003 au col du glacier Coropuna au Pérou (72°39'W, 15°32'S, 6425m) et la deuxième de 122m au sommet du glacier San Valentin au Chili (46°35'S, 73°19'W, 4032m) en 2007. L'étude a porté sur la représentativité du signal isotopique comme archive du climat sur le dernier siècle, correspondant à la totalité de la carotte du Coropuna et les 70 premiers mètres au San Valentin, dans deux régions climatiques différentes. Nous avons observé que les enregistrements des signaux isotopiques sont affectés par des processus de post-dépôt. Au col du Coropuna, le signal est lissé par homogénéisation en dessous de 3m de profondeur à cause de la percolation d'eau de fonte et de la diffusion isotopique via un flux de vapeur, et aucune interprétation climatique n'est possible à partir du signal isotopique. Au so mmet du San Valentin, les vents forts, présents toute l'année, érodent et/ou redistribuent la majorité des précipitations annuelles en créant certainement des hiatus sur une voire plusieurs années ou, au contraire, des dépôts exceptionnels de plusieurs mètres. Ces conditions rendent l'identification des cycles isotopiques annuels difficile et aucune relation entre les isotopes et les paramètres climatiques n'a pu être établie due à une datation très incertaine. / This work is focused on the analyses of two new isotopic records (d18O and dD) from Andean ice cores in the subtropics and temperate latitudes. The first 42 m-long ice core was extracted in 2003 from the saddle of Coropuna glacier in Peru (72°39'W, 15°32'S, 6425 m), and the second 122 m-long core in 2007 from the San Valentin summit in Chile (46°35'S, 73°19'W, 4032 m). The isotopic signals were investigated for their suitability as climate archives over the last century, covering the 42 m-long ice core from Coropuna and the first 70 meters of the core from San Valentin, in two different climatic regions. We observed that the isotopic records are affected by post-depositional processes. At the saddle of Coropuna, isotopic homogenization occurs below 3 m as a result of meltwater percolation and isotopic diffusion, and thus the climatic interpretation is not possible. At the San Valentin summit, removal and/or re-deposition of snow by strong winds occurring throughout the year may create a lack of one or more annual snow layers or, on the other hand, may cause unexpected deposits of several meters. Due to these potential conditions, we cannot always identify the annual isotopic cycles and the isotopes histories show no significant correlation with the climatic parameters because of an uncertain dating.