每一個沿岸國皆多多少少擁有島嶼，不論是近岸島嶼或洋中島嶼。而全球島嶼面積共3,823,000平方英里，佔地表的百分之七(不包括內陸河流及湖泊中之島嶼)，有些國家甚至完全由島嶼構成。據統計，全球島嶼中，大於1,000平方英里者(相當於牙買加或賽浦路斯的大小)者至少有123個，其中共有61個面積達4,000平方英里(相當於盧森堡的大小)者。這些數據顯示了島嶼地位的重要性，因為在今日，島嶼的存在已不再只是一個單純的地理問題，在國際海洋法上，它不僅可以影響一國海域管轄權(領海、鄰接區、專屬經濟區和大陸礁層)的劃定，甚至足以引起海岸相鄰或相向國家海域管轄權的衝突。解決海域管轄權衝突的最基本辦法，即為針對重疊 區域的「平均分攤」。但此一「平均分配」有時反會因島嶼的存在而導致「不公平劃界」或「疆界線的扭曲」。由於上述結果易使當事國之一方劃得不成比例的海域，[甚至引發更複雜的海域糾紛，因此有必要在海疆劃界中適當控制島嶼的海域管轄權，即---藉賦與島嶼適當之效力，以達公平劃界之目的。本文之研究動機即在於此。而研究目的，則在於就公約規定、學者意見、國際司法判例及國家實踐四者，探討島嶼對海疆劃界的影響，找出解決島嶼造成劃界不公平之方，以及賦與島嶼適當效力之道。本文第一章為「島嶼」的概念性介紹，即何謂島嶼，其定義、種類、存在的形式及形成的過程為何?而一般所謂的島嶼與國際法上的島嶼又有何分別? 此皆為本章重點。第二章為島嶼與領海的關係，討論的焦點包括:(一)領海基線的劃定與島嶼的關係、(二)海灣島嶼的效力、(三)島嶼對領海劃界原則的影響以及(四)島嶼在海岸相鄰或相向國家領海劃界中可得之效力程度等等。三章重點在於介紹島嶼與大陸礁層、專屬經濟區劃界原則之關係，並從公約規定、學者意見、國際司法判例及國家實踐等方面探討島嶼存在時，大陸礁層與專屬經濟區的衡平劃界，以及島嶼在「衡平考量﹞U應得的效力。第四章除介紹「群島制度」的內涵，主要重點則為(一)關於劃定群島基線的國家實踐，以及(二)群島基線的劃定對劃界的影響。此外 南海問題亦是本章重點之一。

Continental margin sediments play an important role in marine biogeochemical cycles, partly due to high primary production rates and efficient export of organic matter to sediments in margin environments. This thesis presents studies of solute exchange in fine-grained sediments representative of slope and rise environments, and carbon and nitrogen cycling in sandy sediments dominant in continental shelves worldwide. Results of these studies advance understanding of the role of benthic processes on marine ecosystems. In fine-grained sediments, solute exchange by diffusion, biological mixing and bioirrigation can be quantified using in situ flux chambers with inert tracer additions. Mechanistic models of chamber tracer transport across the seabed indicate that in organic-rich sediments, bioirrigation and mixing dominate over a wide range of bottom water oxygen levels, reflecting the patchiness and versatility of benthic macrofaunal communities. Positive correlations between benthic oxygen and tracer fluxes appear site-specific. Reliable chamber volume estimates derived from mechanistic models reveal that empirical fits to chamber tracer datasets may overestimate chamber volume and benthic solute fluxes. The biogeochemistry of sandy, highly permeable sediments that dominate continental shelves is largely unknown because of the difficulty in sampling and studying them under natural conditions. Novel sediment reactors were developed and used to mimic in situ porewater advection and natural sedimentary conditions. Compositional changes of natural seawater, with and without the addition of

Carbonate platforms contain a wealth of information regarding the changing biota, sea level, ocean-chemistry, and climate of the Cretaceous Period. The Comanche platform of the northern Gulf of Mexico represents a vast, long-lived carbonate system that extended from west Texas through the Florida panhandle. In central and south Texas, excellent outcrops and an extensive suite of subsurface data provide an opportunity to document the evolution of this system, from the shoreline to the shelf-margin and slope. This study examines the changing facies, platform morphologies, and shelf-margin architectures of the mixed carbonate-siliciclastic, middle-Hauterivian to lower-Campanian interval. Stratigraphic results are integrated with stable-isotope geochemistry to document the detrimental effects of oceanic anoxic events on the carbonate platform. Seven second-order, transgressive-regressive supersequences of 3-14 Myr duration are defined in south Texas using sequence stratigraphic analysis of shelf-interior facies successions. Second-order supersequences are subdivided into several third-order depositional sequences of 1-3 Myr duration. In these sequences, facies proportions and stratal geometries of the shelf-interior are found to be the result of changing platform morphology and temporal evolution from distally-steepened ramp to rimmed-shelf depositional profiles. Shelf-margin trajectories, stratigraphic architectures, and facies proportions are a function of long-term accommodation trends expressed in second-order supersequences. These characteristics are modified by lateral variability in the underlying structural/tectonic setting and localized syndepositional faulting. The stratigraphic equivalents of oceanic anoxic events 1a, 1b, 1d, 2, and 3 are documented in the Cretaceous section of south Texas. These oceanic anoxic events coincided with maximum flooding zones of supersequences and are linked to carbonate platform drowning events on four separate occasions. The occurrence of oceanic anoxic events is found to be a fundamental driver of carbonate platform morphology, faunal composition, and facies evolution in transgressive-regressive supersequences of the northern Gulf of Mexico. / text

The objective of this dissertation is to gain a better understanding of the environmental and climatic effects on the temporal and spatial variability of phytoplankton biomass along the West Florida Shelf. Chapter 1 examines temporal and spatial patterns in chlorophyll concentrations using satellite data collected between 1997 and 2003. Chlorophyll data derived from the SeaWiFS sensor are validated with in-situ data and analyzed. Wind, current, sea surface temperature, river, and rain data are used to better understand the factors responsible for the patterns observed in the satellite data. My question is whether the standard OC4 algorithm is adequate for studying short-term variability of chlorophyll concentrations along the WFS. I will examine temporal and spatial trends using the OC4 and compare them to the Carder semianalytical algorithm which uses remote sensing reflectances at 412nm, 443nm, 490nm,and 555nm to estimate chlorophyll concentrations separately from CDOM estimates. In Chapters 2 and 3 the potential problems due to CDOM and bottom reflectance are examined. In Chapter 2 I analyze the influence of riverine induced CDOM. Water leaving radiances are analyzed in an effort to discriminate true chlorophyll patterns from CDOM contaminated signals. Chapter 3 examines the impact of bottom reflectance on the satellite signal by using the percentage of remote sensing reflectance at a wavelength of 555 to differentiate between optically shallow waters and optically deep waters. Optically shallow waters are defined as those with the percentage of Rrs at 555 due to bottom reflectance greater than or equal to 25 percent, while optically deep waters have percent bottom reflectance less than or equal to 25 percent. These analyses will help assess the validity of the temporal and spatial patterns ofchlorophyll concentration observed with the SeaWiFS data described in Chapter 1.

This thesis examines the utility of the Rényi entropy (RE), a measure of the complexity of probability density functions, as a tool for finding physically meaningful patterns in geophysical data. Initially, the RE is applied to observational data of long-lived atmospheric tracers in order to analyse the dynamics of stratospheric transitions regions associated with barriers to horizontal mixing. Its wider applicability is investigated by testing the RE as a method for highlighting internal boundaries in snow and ice from ground penetrating radar (GPR) recordings. High-resolution 500 MHz GPR soundings of dry snow were acquired at several sites near Scott Base, Antarctica, in 2008 and 2009, with the aim of using the RE to facilitate the identification and tracking of subsurface layers to extrapolate point measurements of accumulation from snow pits and firn cores to larger areas. The atmospheric analysis focuses on applying the RE to observational tracer data from the EOS-MLS satellite instrument. Nitrous oxide (N2O) is shown to exhibit subtropical RE maxima in both hemispheres. These peaks are a measure of the tracer gradients that mark the transition between the tropics and the mid-latitudes in the stratosphere, also referred to as the edges of the tropical pipe. The RE maxima are shown to be located closer to the equator in winter than in summer. This agrees well with the expected behaviour of the tropical pipe edges and is similar to results reported by other studies. Compared to other stratospheric mixing metrics, the RE has the advantage that it is easy to calculate as it does not, for example, require conversion to equivalent latitude and does not rely on dynamical information such as wind fields. The RE analysis also reveals occasional sudden poleward shifts of the southern hemisphere tropical pipe edge during austral winter which are accompanied by increased mid-latitude N2O levels. These events are investigated in more detail by creating daily high-resolution N2O maps using a two-dimensional trajectory model and MERRA reanalysis winds to advect N2O observations forwards and backwards in time on isentropic surfaces. With the aid of this ‘domain filling’ technique it is illustrated that the increase in southern hemisphere mid-latitude N2O during austral winter is probably the result of the cumulative effect of several large-scale, episodic leaks of N2O-rich air from the tropical pipe. A comparison with the global distribution of potential vorticity strongly suggests that irreversible mixing related to planetary wave breaking is the cause of the leak events. Between 2004 and 2011 the large-scale leaks are shown to occur approximately every second year and a connection to the equatorial quasi-biennial oscillation is found to be likely, though this cannot be established conclusively due to the relatively short data set. Identification and tracking of subsurface boundaries, such as ice layers in snow or the bedrock of a glacier, is the focus of the cryospheric part of this project. The utility of the RE for detecting amplitude gradients associated with reflections in GPR recordings is initially tested on a 25 MHz sounding of an Antarctic glacier. The results show distinct regions of increased RE values that allow identification of the glacial bedrock along large parts of the profile. Due to the low computational requirements, the RE is found to be an effective pseudo gain function for initial analysis of GPR data in the field. While other gain functions often have to be tuned to give a good contrast between reflections and background noise over the whole vertical range of a profile, the RE tends to assign all detectable amplitude gradients a similar (high) value, resulting in a clear contrast between reflections and background scattering. Additionally, theoretical considerations allow the definition of a ‘standard’ data window size with which the RE can be applied to recordings made by most pulsed GPR systems and centre frequencies. This is confirmed by tests with higher frequency recordings (50 and 500 MHz) acquired on the McMurdo Ice Shelf. However, these also reveal that the RE processing is less reliable for identifying more closely spaced reflections from internal layers in dry snow. In order to complete the intended high-resolution analysis of accumulation patterns by tracking internal snow layers in the 500 MHz data from two test sites, a different processing approach is developed. Using an estimate of the emitted waveform from direct measurement, deterministic deconvolution via the Fourier domain is applied to the high-resolution GPR data. This reveals unambiguous reflection horizons which can be observed in repeat measurements made one year apart. Point measurements of average accumulation from snow pits and firn cores are extrapolated to larger areas by identifying and tracking a dateable dust layer horizon in the radargrams. Furthermore, it is shown that annual compaction rates of snow can be estimated by tracking several internal reflection horizons along the deconvolved radar profiles and calculating the average change in separation of horizon pairs from one year to the next. The technique is complementary to point measurements from other studies and the derived compaction rates agree well with published values and theoretical estimates.

During the Late Pliocene and early Pleistocene, when the paleo-Orinoco delta system transited over the Amacuro Shelf and reached the paleo-shelf-break along the southeastern shoreline of Trinidad. At this time onwards, the shelf-edge delta clinoforms developed further eastward. These deltaic clastic wedges serve as the unique analog in the geological record for an accommodation-driven inner-shelf and shelf-edge delta, developed at an oblique foreland tectonic setting situated at a tropical-equatorial paleogeographic setting. These deposits were influenced by strong Atlantic longshore current, tropical storms, and phytodetrital pulses, and with an exceptionally high sediment accumulation rates. These four aspects make the clastic wedges unique candidates for sedimentological, ichnological, and stratigraphic investigation. The primary objectives of this thesis are to: (a) collect, analyze, and integrate outcrop data on lithofacies, trace fossils, and discontinuity surfaces into a comprehensive depositional and ichnological model for the first growth-fault-guided shelf-marginal pulse of the paleo-Orinoco delta, as recorded in the Mayaro Formation outcrops in southeast Trinidad; and (b) deduce the dominant sedimentary processes during the across shelf transit and their impacts on the benthic infauna as preserved in the Morne L’Enfer Formation outcrops of southwest Trinidad, which are possibly slightly older than the Mayaro Formation. The basal interval of the Morne L’Enfer Formation has specifically been investigated for this purpose, where the deltaic clastic wedges are preserved directly above shelf deposits. The entire Mayaro Formation megasequence is categorized into deposits belonging to twelve different subenvironments based on lithofacies associations and ichnological characteristics. Ichnological evidence indicates that the shelf-edge deltas are one of the most extreme marine environments for benthic metazoans to colonize. However, the combinations and ranking of stress factors affecting the colonizing fauna are diverse and distinct in every individual subenvironment indicating the relative dominances of river-influence, waves, and/or sediment-gravity-flows vis-à-vis slope instability. Due to variations in stress factors, the megasequence also displays dual ichnologic and sedimentologic properties of both the shelf-edge delta lobe(s) and the outer shelf delta lobe(s). A minor transient tidal influence can only be observed in the architectural elements, e.g. elongated interbar embayment and interlobe prodeltaic depocentres, which control topography and enhance tidal effect. Discovery of an unusual monospecific Glossifungites Ichnofacies along an incision surface in the midst of the Mayaro Formation succession enabled a substantial overhaul of the earlier understanding of the formation in terms of its depositional model and stacking pattern. The surface has been re-identified as a canyon/gully cut at the shelf-edge, which possibly acted as a conduit for (a) the mass movements and for (b) the coarse clastic (mostly silt to medium-grained sand) sediment transfer to deep marine settings. The monospecific nature of the Glossifungites Ichnofacies suite indicates that the incision surface was under substantial ecological stresses for the colonizing infauna. The stresses might have arisen from slope instability of the steep canyon/gully walls, mass movements above the incision surface, elevated water turbulence, and lowered salinity from river influx. Five different facies tracts have been identified within the canyon/gully-fill, which crosscuts the shelf-edge delta-front. The facies tracts are dominated by different types of sediment-gravity flow deposits, which are systematically stacked and are almost devoid of trace fossils due to rapid sedimentation rates and slope instability. They are also strikingly different from the surrounding deltaic facies. A high-frequency sequence stratigraphic model involving the influence of growth-fault tectonics on the relative sea-level curve has been invoked to explain the incision of the canyon/gully and its sequential filling processes. On the other hand, the transition from the open shelf to inner-shelf deltaic condition as displayed by the basal members of the Morne L’Enfer Formation is strongly dominated by evidences of river influence with the transient background action of fair-weather waves and storm waves. A peculiar pattern of disappearance of trace fossils produced by irregular sea-urchins highlight that the river influence was quite strong not only at the sediment-water interface but also in the water-column, which affected invertebrate larvae. The initial progradation of the clastic wedge on the shelf was dominated by hyperpycnal flows and waves in contrast to tidal domination in the younger members of the formation.

Este estudo tem como objetivo estudar o fósforo total e as especiações de fósforo nos sedimentos superficiais associados aos processos biogeoquímicos em dois sistemas estuarinos, na plataforma continental sudeste e na região polar antártica. Amostras de água de fundo foram coletadas em dois períodos sazonais (verão-inverno) nos estuários sob diferentes graus de impacto ambiental antrópico. A metodologia de extração das frações de (SEDEX) aplicada para obter as especiações químicas de fósforo foi testada com padrões certificados antes das análises. Os resultados foram reprodutivos e a eficiência da extração foi aceitável. As concentrações das espécies químicas de fósforo sedimentar nos dois estuários mostraram diferenças entre os setores seguindo as características granulométricas, influência da maré, condições redox das águas de fundo bem como, as ações antrópicas reveladas pelos dados quantitativos e qualitativos. Uma influência sazonal mínima foi observada. No caso da plataforma sudeste, altos valores de matéria orgânica foram observados em núcleos ao longo da plataforma, junto às estações externas das radiais de Santos e Ilha Grande mostrando uma diferenciação acompanhada pelas frações de fósforo orgânico e carbono orgânico. Nas demais radiais, altos valores de CaCO3 foram observados nas estações mais externas. Na Baía do Almirantado as frações predominantes foram P mineral, P detrítico, P-ligado à apatita autigênica, sendo que a forma orgânica foi baixa e associada a baixos valores de carbono orgânico. A quantificação e distribuição das espécies de fósforo nos sedimentos constituem importante ferramenta para compreender o ciclo biogeoquímico do fósforo e dos demais nutrientes nos ecossistemas marinhos. / This work aims to study the total and chemical species of phosphorus in the surface sediments associated to the biogeochemical processes in two estuarine systems, the southeastern continental shelf and Antarctic polar region. Bottom water samples were collected in two seasonal periods (summer-winter) in the estuaries under different degrees of environmental anthorpic impacts. The fraction extraction methodology (SEDEX) applied to obtain the chemical phosphorus species was tested in relation to the certified standards before analyses. The results were reproductive and the extraction efficiency was acceptable. The chemical species concentrations of sedimentary phosphorus in the two estuarine systems showed differences between sectors following the granulometric characteristics, tide influence, redox conditions of the bottom waters as well as anthropic actions revealed by quantitative and qualitative data. A minimum seasonal influence was observed. In the case of eastern continental shelf, high values of organic matter were found in nuclei distribution along the platform in the external stations of Santos and Ilha Grande radials showing a differentiation accompanied by organic phosphorus and C org., fractions. In the other radials high CaCO3 values were observed in the external stations. In the Admiralty Bay the predominant fractions were detrital apatite and authigenic/biogenic apatite, being that organic form was low, linked to low values of organic carbon. The quantification and distribution of P species in the sediments constitute important tools to understand the P and the other nutrient biogeochemical cycles in the sea ecosystems

Submitted by Maike Costa (maiksebas@gmail.com) on 2017-09-06T12:43:49Z No. of bitstreams: 1 arquivototal.pdf: 4989490 bytes, checksum: e588d94dcdcc484ca970d62d2e581dd7 (MD5) / Made available in DSpace on 2017-09-06T12:43:49Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 4989490 bytes, checksum: e588d94dcdcc484ca970d62d2e581dd7 (MD5) Previous issue date: 2016-08-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The aim of this study was to evaluate the inclusion of chitosan and modified chitosan (chitosan-glucose) in appropriate concentration to meet the health claim in sausages with reduced fat, on the technological functionality and shelf life of these sausages. For this, an initial study was conducted, in which chitosan (2% w/w) was added to sausages prepared with pork and three levels of fat (5%, 12.5% and 20% w/w). The sausages were submitted to cold storage at 4 ± 1 °C for 15 days and evaluated in terms of microbiological, physic-chemical and sensory parameters. Subsequently, considering the absence of studies on incorporation of chitosan in meat goat products, carried out a second study, similar to the above to evaluate the effect of incorporation of chitosan (2% w/w) in sausage made with goat meat, and similar levels of fat in the microbiological and physico-chemical quality during cold storage (4 ± 1 °C) for 15 days. Finally, in the third study was evaluated the effect of the derivative of chitosan (2% w/w) in comparison with chitosan base (2% w/w) in sausage made with goat meat and reduced fat content (10% w/w). The sausages were stored at 4 ± 1 ° C for 21 days and evaluated by microbiological, physic-chemical and sensory parameters. In all three studies a formulation without the addition of polymers (chitosan and modified chitosan) was used as control. The results indicated that the use of 2% (w / w) chitosan and its derivative (corresponding to 1 g of chitosan per sausage of 50g each in a portion of 150g) to ensure ingestion of 3 g of chitosan per day is technologically feasible for use in the preparation of sausage with pork and goat meat. In addition to the functional potential, chitosan and chitosan derivative provided increased stability of the treated sausages since it caused the reduction of microbial growth when compared to the control sample. Additionally, they provided an improvement in red color, resulting in positive effects on the appearance, a more stable emulsion for the greater ability to bind water and fat, and a firmer texture to increase the compression forces, without negatively affecting the sensory properties of sausages. The chitosan and modified chitosan showed similar behavior, but the use of chitosan resulted in higher antioxidant activity than its derivative, considering further reduction of TBARS values and increased content of unsaturated fatty acids and poly-unsaturated. However, the chitosan derivative promoted a greater red color (a *) and lower hardness than chitosan. Therefore, the results of the use of chitosan in the manufacture of goat sausages, which was studied for the first time, indicated that the chitosan and modified chitosan showed potential interest to be used in the preparation of meat products, since they can provide higher quality and shelf life, adding value to the raw material of low commercial value, besides allow to obtain of a functional product with the health claim and fat reduction. / O objetivo deste estudo foi avaliar a inclusão da quitosana e quitosana modificada (quitosana-glicose), em concentração adequada para atender a alegação de saúde, em salsichas com reduzido teor de gordura, sobre a funcionalidade tecnológica e a vida de prateleira destas salsichas. Para isso, um primeiro estudo foi realizado, no qual a quitosana (2 % m/m) foi adicionada em salsichas elaboradas com carne suína e três níveis de gordura (5%, 12,5% e 20%, m/m). As salsichas foram submetidas ao armazenamento refrigerado a 4 ± 1 ºC por 15 dias e avaliadas em relação aos parâmetros microbiológicos, físico-químicos e sensoriais. Posteriormente, considerando a inexistência de estudos sobre a incorporação de quitosana em produtos cárneos caprino, realizou-se um segundo estudo, semelhante ao anterior, para avaliar o efeito da incorporação da quitosana (2 % m/m) em salsicha elaborada com carne caprina e similares níveis de gordura na qualidade microbiológica e físico-química durante o armazenamento refrigerado (4 ± 1 ºC) por 15 dias. Por fim, no terceiro estudo foi avaliado o efeito do derivado da quitosana (2% m/m), comparando com a quitosana base (2% m/m), em salsicha elaborada com carne caprina e reduzido teor de gordura (10% m/m). As salsichas foram armazenadas a 4 ± 1 ºC por 21 dias, e avaliadas nos parâmetros microbiológicos, físico-químicos e sensoriais. Nos três estudos uma formulação sem adição dos polímeros (quitosana e quitosana modificada) foi usada como controle. Os resultados indicaram que o uso de 2% (m / m) de quitosana e seu derivado (correspondendo a 1 g de quitosana por salsicha de 50g cada em uma porção de 150g) para garantir a ingestão de 3 g de quitosana por dia é tecnologicamente viável para uso na elaboração de salsicha com carne de porco e cabra. Além do potencial funcional, a quitosana e o derivado da quitosana proporcionaram aumento da estabilidade das salsichas tratadas, uma vez que provocaram a redução do crescimento microbiológico quando comparadas a amostra controle. Adicionalmente, proporcionaram uma melhoria na cor vermelha, resultando em efeitos positivos na aparência, uma emulsão mais estável, pela maior capacidade de ligar água e gordura, e uma textura mais firme por aumentar as forças de compressão, sem afetar negativamente as propriedades sensoriais das salsichas. A quitosana e a quitosana modificada mostraram comportamento semelhante, mas o uso da quitosana resultou em maior atividade antioxidante do que o seu derivado, considerando a maior redução dos valores de TBARS e maior teor de ácidos graxos insaturados e poli-insaturados. Entretanto, o derivado da quitosana promoveu maior cor vermelha (a*) e menor dureza que a quitosana. Portanto, os resultados da utilização da quitosana na fabricação de salsichas caprina, a qual foi estudada pela primeira vez, indicaram que a quitosana e a quitosana modificada apresentaram potencial interessante para serem utilizados na elaboração de produtos cárneos, uma vez que podem proporcionar maior qualidade e vida de prateleira, agregando valor à matéria-prima de baixo valor comercial, além de permitir a obtenção de um produto funcional com alegação de saúde e redução de gordura.

La calotte polaire Antarctique conditionne un flux d’eau douce dans l’océan Austral par deux voies d’égale importance : une injection immédiate et localisée par fonte des plateformes glaciaires, et une injection « offshore » et différée par production (« vêlage ») puis fonte d’icebergs. On estime ainsi que les icebergs, en fondant, pourraient modifier les caractéristiques hydrologiques et biogéochimiques de la colonne d’eau. Les modèles numériques visant à estimer cet impact présentent des résultats contrastés. Ils sont limités dans leurs stratégies de représentations des icebergs, notamment parce que les connaissances sur la distribution spatiale et de taille des icebergs ou encore leurs mécanismes de perte de masse sont réduites. Une méthode récente exploitant des mesures par altimétrie satellitaire a permis la création d’une base de données cartographiant la distribution des icebergs Antarctiques avec une couverture spatiale et temporelle inédite. Notre analyse conjointe entre ces données et des champs de concentration en glace de mer met en lumière le transport d’eau douce injecté par les icebergs et son impact sur la banquise. On analyse également les liens entre icebergs de différentes tailles : les gros peuvent être vus comme des réservoirs de volume de glace, qu’ils diffusent dans tout l’océan en se fragmentant en petits icebergs de différentes tailles. On étudie alors l’évolution de deux icebergs géants, on propose une première paramétrisation du phénomène de fracturation et analyse la distribution de taille résultante. Ces résultats peuvent permettre une représentation plus réaliste du flux d'eau douce conditionné par les icebergs dans les modèles. / The Antarctic polar ice cap constrains a freshwater flaux into the Austral Ocean through two equally important pathways : a localized and immediate injection through the melting of ice-shelves bases, and a delayed offshore injection through the calving and subsequent melt of icebergs. Some studies reckon that melting icebergs have the capacity to alter the hydrological and biogeo-chemical characteristics of the water column. The numerical models trying to evaluate this impact have shown contrasting results. Yet, they might suffer from a poor representation of the icebergs, namely due to our limited knowledge on both the spatial and size distributions of the icebergs, or even the processes involved in their mass loss. A new method using satellite altimetry measurements has lead to the creation of a database mapping Antarctic icebergs distribution with an unprecedented spatial and temporal coverage. Our joint analysis between these data and sea ice concentration fields highlights a possible transport of the freshwater injected by an iceberg and its impacts on sea ice.We also analyze the links between icebergs of different sizes : the large ones can be seen as ice buffers that diffuse across the whole ocean when breaking into small fragments of various sizes. We finally study the evolution of two giant icebergs, suggest the first parametrization of the fragmentation process and analyze the subsequent size distribution of the fragments. These results can be valuable to account in a more realistic way the fresh water flux constrained by icebergs in models.

Made available in DSpace on 2015-03-13T17:08:41Z (GMT). No. of bitstreams: 1 SamiaFL.pdf: 2363626 bytes, checksum: 8067b8065fc31135e35d263ce60bc5e0 (MD5) Previous issue date: 2006-03-15 / The brazilian marginal basins have a huge potential to generate and accumulate petroleum. Incised valleys which are eroded in response to a fall of relative sea level are related to potential reservoir as well, modern drowned-valley estuaries serve as harbors to petroleum and salt industries, fisheries, waste-disposal sites and recreational areas for a significant fraction of the world s population. The combined influence of these factors has produced a dramatic increase in research on modern and ancient incised-valley systems. This research is one expression of this interest. The integrated use of satellites images and high resolution seismic (bathymetry, sides scan sonar) was used on the Apodi River mouth-RN to characterizes the continental shelf This area is located at the Potiguar Basin in the NE Brazilian Equatorial Atlantic margin. Through bathymetric and side scan sonar data processing, a digital Terrain Model was developed, and a detailed geomorphologic analysis was performed. In this way was possible to recognize the geomorphologic framework and differents sismofacies, which may influence this area. A channel extending from the ApodiMossor? river mouth to the shelf edge dominates the investigated area. This structure can be correlated with the former river valley developed during the late Pleistocene sea level fall. This channel has two main directions (NW-SE and NE-SW) probably controlled by the Potiguar Basin structures. The western margin of the channel is relatively steep and pronounced whereas the eastern margin consists only of a gentle slope. Longitudinal bedforms and massive ridges also occur. The first are formed doe to the shelf sediment rework and the reef-like structures probably are relics of submerged beachrock-lines indicating past shoreline positions during the deglacial sea-level rise. The sub-bottom seismic data allow the identification of different sismic patterns and a marcant discontinuity, interpreted as the Upper / As bacias marginais brasileiras t?m um grande potencial gerador e acumulador de petr?leo, em geral associados a um sistema de vales incisos que s?o desenvolvidos em resposta a queda do n?vel do mar. Esses sistemas est?o diretamente relacionados com atividades econ?micas desenvolvidas em regi?es costeiras, como portos para ind?stria petrol?fera, salineira, pesqueira e atividades recreativa para uma significante fra??o da popula??o mundial. Esta disserta??o apresenta a caracteriza??o geomorfol?gica e paleogeogr?fica da plataforma continental brasileira adjacente ? foz do rio Apodi-Mossor?/RN, atrav?s do uso integrado de imagens de sat?lite e geof?sica de alta resolu??o (batimetria, s?smica e sonar de varredura lateral). Essa regi?o est? localizada na Bacia Potiguar, na Margem Equatorial Atl?ntica. A partir dos dados batimetricos, foi confeccionado e aferido um modelo digital de terreno (MOT), e desenvolvida uma an?lise geomorfol?gica detalhada, que integrada aos dados hidrodin?micos proporcionou uma melhor compreens?o dos fatores oceanogr?ficos atuantes na regi?o, de forma a entender a resposta geomorfol?gica dessa regi?o afogada pela r?pida subida do n?vel do mar, no Holoceno. A principal fei??o identificada foi um canal submerso na plataforma interna, provavelmente relacionado com o sistema de vales incisos formado durante o rebaixamento do n?vel do mar no Pleistoceno. O canal tem duas dire??es principais (NW-SE e NE-SW), aparentemente controladas pelas estruturas tect?nicas da Bacia Potiguar. A margem oeste do canal ? relativamente soerguida em rela??o ? margem leste. Este soerguimento ? aqui relacionado ? presen?a do Alto de Icapu? a oeste da ?rea. Recifes e dunas submersas tamb?m est?o presentes na ?rea. Os recifes relacionados a estruturas reliquiares submersas como rochas de praia podendo indicar antigas linhas de costa posicionadas durante a subida do n?vel do mar. Com base nos dados s?smicos, foi poss?vel identificar uma descontinuidade presente em todas a ?rea interpretada como o limite Pleistoceno Superior/Holoceno Inferior, bem como sismof?cies referentes a diferentes padr?es de preenchimento e sedimenta??o do canal submerso e da plataforma durante a subida do n?vel do mar no Holoceno