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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Equatorial ocean dynamics impacting upwelling west of the Galápagos Archipelago

Jakoboski, Julie K.(Julie Kathryn) January 2019 (has links)
Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2019 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 131-137). / The Galápagos Cold Pool (GCP) is a region of anomalously cold sea surface temperature (SST) just west of the Galápagos Archipelago. Modeling studies have shown that the GCP is maintained by wind- and current-driven upwelling. The Galápagos Archipelago lies on the equator, in the path of the Pacific Equatorial Undercurrent (EUC) as it flows eastward across the Pacific at the depth of the thermocline. It is hypothesized that the EUC upwells into the GCP as it reaches the topographical barrier of the Galápagos Archipelago. The path of the EUC in the vicinity of the archipelago is not well understood. The 'Repeat Observations by Gliders in the Equatorial Region' (ROGER) program deployed a fleet of Spray autonomous underwater gliders in the region just west of the Galápagos Archipelago from 2013 - 2016 with the goal of continuously occupying three transects that form a closed area, with the archipelago as the eastern boundary. / Gliders obtained subsurface measurements of temperature, salinity, and velocity with unprecedented temporal and spatial resolution. These measurements are used to observe the path of the EUC as it bifurcates into a north and south branch around the Galápagos Archipelago. Net horizontal transport into the volume defined by the closed area formed by the glider transects is used to estimate an average vertical velocity profile in the region of the GCP, indicating upwelling in the upper 300 m. The bifurcation latitude of the EUC, estimated to be approximately 0.4°S from volume transport as a function of salinity, is coincident with the meridional center of the archipelago, suggesting the bifurcation latitude is topographically controlled. Ertel potential vorticity and a Bernoulli function are qualitatively conserved, supporting an inertial model of the EUC. / Average spectral variance from Argo profiling float observations is used to show that tropical instability waves propagate with frequency and wavelength consistent with linearized, equatorial [beta]-plane model results and may impact the GCP, according to their vertical structure. / by Julie K. Jakoboski. / Ph. D. / Ph.D. Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution)
72

Circulation and convection in the Irminger Sea

Våge, Kjetil January 2010 (has links)
Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 131-149). / Aspects of the circulation and convection in the Irminger Sea are investigated using a variety of in-situ, satellite, and atmospheric reanalysis products. Westerly Greenland tip jet events are intense, small-scale wind phenomena located east of Cape Farewell, and are important to circulation and convection in the Irminger Sea. A climatology of such events was used to investigate their evolution and mechanism of generation. The air parcels constituting the tip jet are shown to have a continental origin, and to exhibit a characteristic deflection and acceleration around southern Greenland. The events are almost invariably accompanied both by a notable coherence of the lower-level tip jet with an overlying upper-level jet stream, and by a surface cyclone located in the lee (east) of Greenland. It is argued that the tip jet arises from the interplay of the synopticscale flow evolution and the perturbing effects of Greenland's topography upon the flow. The Irminger Gyre is a narrow, cyclonic recirculation confined to the southwest Irminger Sea. While the gyre's existence has been previously documented, relatively little is known about its specific features or variability. The mean strength of the gyre's circulation between 1991 and 2007 was 6.8 ± 1.8 Sv. It intensified at a rate of 4.3 Sv per decade over the observed period despite declining atmospheric forcing. Examination of the temporal evolution of the LSW layer thickness across the Irminger Basin suggests that local convection formed LSW during the early 1990s within the Irminger Gyre. In contrast, LSW appeared outside of the gyre in the eastern part of the Irminger Sea with a time lag of 2-3 years, consistent with transit from a remote source in the Labrador Sea. In the winter of 2007-08 deep convection returned to both the Labrador and Irminger seas following years of shallow overturning. The transition to a convective state took place abruptly, without going through a preconditioning phase, which is contrary to general expectations. Changes in the hemispheric air temperature, tracks of storms, flux of freshwater to the Labrador Sea, and distribution of pack ice all conspired to enhance the air-sea heat flux, resulting in the deep overturning. / Kjetil Våge. / Ph.D.
73

Modélisation numérique et observations de l'océan global : développement des interfaces, évaluation de simulations et de réseaux d'observations, investigations dynamiques / Océanographie physique,simulations numériques,observations,altimétrie,hydrographie,méthodes statistiques

Juza, Mélanie 15 September 2011 (has links)
L'objectif de cette thèse est de développer des approches statistiques pour l'évaluation systématique et quantitative de simulations océaniques multi-décennales globales à l'aide d'observations altimétriques et hydrographiques. La première étape consiste à extraire des simulations la contrepartie exacte (en temps et en espace) des observations pour construire des données synthétiques. La comparaison entre les données observées et simulées colocalisées permettent d'évaluer les simulations et de les comparer entre elles par rapport à des références communes (observations). De plus, la comparaison entre les sorties des modèles considérées chaque point de grille et colocalisées permet d'évaluer l’impact du sous-échantillonnage des réseaux d’observations sur l'estimation de certaines quantités océaniques importantes pour le climat. Nous quantifions l'impact de la résolution de nos modèles (2°, 1°, ½°, ¼°) sur le réalisme des simulations au regard des observations. Résoudre une gamme d'échelles spatio-temporelles plus large améliore de façon significative la représentation de la circulation océanique moyenne, de la structure thermohaline, de la variabilité saisonnière de la couche de mélange et de la variabilité du niveau de la mer sur plusieurs échelles spatio-temporelles, notamment à l'échelle interannuelle. Ce résultat nouveau montre l’intérêt d’utiliser un modèle au 1/4°, capable de représenter en partie la méso-échelle, pour les scénarios climatiques. Nous mettons également en évidence la capacité du modèle au 1/4° à simuler une variabilité interannuelle intrinsèque du niveau de la mer, non corrélée avec les observations en raison de son caractère chaotique, mais probablement réaliste et nécessaire pour mieux représenter l'intensité de la variabilité interannuelle.A l’aide des simulations, nous montrons également que l'inhomogénéité de la couverture spatio-temporelle du réseau d'observations Argo induit une surestimation des profondeurs et des contenus thermiques de la couche de mélange, et que les limitations géographiques du réseau actuel induisent des biais en amplitude sur les estimations des variabilités saisonnière et interannuelle du contenu thermique de l'océan global. / This work aims to develop statistical approaches to systematically and quantitatively assess 50-year global ocean simulations against altimetric and hydrographic observations. Simulation outputs are first sub-sampled exactly like observations to build pseudo (synthetic) observations. We use collocated misfits between synthetic and real observations to assess the simulations at the same dates and locations, and compare the simulations together. We then use the sub-sampled and fully sampled model outputs to assess the impact of sub-sampling in real observing systems on the estimation of oceanic quantities with climatic relevance. We first quantify how the resolution of our ocean models (2°, 1°, ½°, ¼°) affects the realism of their solutions with respect to both observational datasets. We quantify how broadening the range of resolved space scales significantly improves the representation of the mean surface circulation, the thermohaline structure, the seasonal cycle of mixed layers, as well as sea-surface height variability at most space and time scales; this is particularly the case at interannual time scales, highlighting the potential of eddy-permitting resolutions for climate simulations. We also show the capacity of the 1/4° model to simulate an interannual intrinsic variability of sea-level, decorrelated from observed timeseries because of its chaotic character, but probably realistic and necessary to better represent the intensity of the interannual variability.The simulations also show that the spatio-temporal dispersion of the Argo floats induces overestimations of the mixed layer depths and heat contents, and the geographical restrictions of the actual Argo array induce biases in amplitude on the seasonal and interannual variabilities of the global ocean heat content.
74

Development Of Gis-based National Hydrography Dataset, Sub-basin Boundaries, And Water Quality/quantity Data Analysis System For Turkey

Girgin, Serkan 01 December 2003 (has links) (PDF)
Computerized data visualization and analysis tools, especially Geographic Information Systems (GIS), constitute an important part of today&amp / #65533 / s water resources development and management studies. In order to obtain satisfactory results from such tools, accurate and comprehensive hydrography datasets are needed that include both spatial and hydrologic information on surface water resources and watersheds. If present, such datasets may support many applications, such as hydrologic and environmental modeling, impact assessment, and construction planning. The primary purposes of this study are production of prototype national hydrography and watershed datasets for Turkey, and development of GIS-based tools for the analysis of local water quality and quantity data. For these purposes national hydrography datasets and analysis systems of several counties are reviewed, and based on gained experience / 1) Sub-watershed boundaries of 26 major national basins are derived from digital elevation model of the country by using raster-based analysis methods and these watersheds are named according to coding system of the European Union, 2) A prototype hydrography dataset with built-in connectivity and water flow direction information is produced from publicly available data sources, 3) GIS based spatial tools are developed to facilitate navigation through streams and watersheds in the hydrography dataset, and 4) A state-of-the art GIS-based stream flow and water quality data analysis system is developed, which is based on the structure of nationally available data and includes advanced statistical and spatial analysis capabilities. All datasets and developed tools are gathered in a single graphical user-interface within GIS and made available to the end-users.
75

Hydrodynamic modelling of Delta Marsh and simplified methods of discharge estimation for discontinuous inland coastal wetlands

Aminian, Parsa 09 January 2016 (has links)
This thesis details the hydrodynamic research conducted at Delta Marsh as part of the Restoring the Tradition marsh rehabilitation project. Research has indicated that the hydraulic and hydrologic controls on the marsh can have considerable impacts on its ecological function, but the impacts of these controls had not previously been studied. Field hydrography and two-dimensional numerical modelling (using MIKE 21) provided insight into many aspects of the physical behaviour of Delta Marsh. Eighty five percent of the inflow to Delta Marsh from Lake Manitoba passes through Clandeboye Channel, and these discharge signals propagate as far west as Cadham Bay. Inflow to the marsh disperses quickly, and accounts for a small fraction of the water that exits the marsh during subsequent outflow. Thus, Portage Diversion water that enters the marsh through the lake can remain there even if there is a net loss in marsh volume over the season. Wind friction across Lake Manitoba has the greatest impact on short-term fluctuations in marsh volume and on the composition of marsh water, followed by the Portage Diversion and the natural inflows to Lake Manitoba. Expansions to flood diversion infrastructure will considerably impact the composition of Delta Marsh waters. Three methods of wetland discharge estimation were developed and tested. The most promising method was the regressed slope Manning method (RSMM), which estimates two-directional channel discharge as a function of the water surface elevations at both ends of a channel. When used in conjunction with the velocity index method, the RSMM can multiply the amount of reliable discharge data collected per research dollar. Thanks to its simple formulation, the RSMM is likely applicable outside of wetland settings, as well. / February 2016
76

Análise morfométrica e biodiversidade da vegetação na microbacia hidrográfica da Fazenda Experimental Edgárdia

Moreira, Lilian [UNESP] 22 June 2007 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:26:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-06-22Bitstream added on 2014-06-13T18:30:33Z : No. of bitstreams: 1 moreira_l_me_botfca.pdf: 1316321 bytes, checksum: 74863b03a739d682b82d64ce1f23a265 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / The preservation of the biodiversity of the vegetation in the micro watershed is of basic importance for the maintenance of the animal and vegetal wild life, ambient services and protection of the biosfera. The morphometry is a tool of great importance as diagnostic of susceptibility to the ambient degradation or conservation and guides the planning and handling of the micro watershed. The present study had as objective the morphometric characterization and analysis of biodiversity in the micro watershed of the Edgárdia Farm, Botucatu - SP. The micro watershed of the Edgárdia Farm belongs to the College of Agronomicas Ciencias/UNESP, city of Botucatu - SP. The program used for the attainment of the morphometrical variable was the ILWIS 3.2 version and the topographical letter of the IBGE with 1:50.000 scale. In the study of biodiversity four transects in the micro watershed had been installed, in the parts high (superior third), medium high and medium low (medium third) and low (inferior third) of the micro watershed, in which parcels of 10 x 5 meters had been installed. In the four transects, the forest species had been quantified and commanded in popular and classified families, species, names in its respective ecological successions (pioneer, secondary or climax). It was measured in each tree the height and the diameter in the height of the chest (DAP). The morphometrical variable and the results were: area of 7,205 kmø; perimeter of 11,59 km; length and width of micro watershed 3,578 the equal 3,016 km; length of the draining net and quotas of 15,68 km and 1100,00 km; factor of form 0,79, considered very high; density of draining of 2,18 km.kmø, classified as average; the high declivity of 76,98%, in accordance with the classes of declivities and types of relief of the micro watershed, was classified as scarped; frequency of rivers the 3,19 segments of rivers... (Complete abstract click electronic access below)
77

Meio ambiente e agricultura na microbacia hidrográfica do Córrego Palmitalzinho - Regente Feijó/São Paulo

Golla, Amarílis Rós [UNESP] 05 December 2006 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:24:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-05Bitstream added on 2014-06-13T18:48:39Z : No. of bitstreams: 1 golla_ar_me_prud.pdf: 1858401 bytes, checksum: 19a2eedb3dd7b43c07d8803318256180 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O manejo adequado de solos e água é imprescindível para a manutenção da qualidade ambiental e de vida da população. Entretanto, isso não vem ocorrendo na microbacia hidrográfica do córrego Palmitalzinho -Regente Feijó/São Paulo. Nessa área, são encontrados diversos problemas ambientais, tais como, baixa fertilidade e compactação do solo, erosão e assoreamento dos cursos d'água. Em função disto, neste trabalho teve-se como objetivos: levantar as atividades agropecuárias e sua disposição espacial na microbacia hidrográfica do córrego Palmitalzinho; identificar aspectos negativos associados ao manejo inadequado dos recursos naturais; propor práticas de conservação e manejo dos recursos solo e água e levantar as atividades desenvolvidas pelo Programa Estadual de Microbacias Hidrográficas. Para atingir os objetivos foram realizados levantamentos de campo em todas as propriedades, entrevistas com os proprietários/funcionários das mesmas, assim como coletas de dados e informações em órgãos públicos envolvidos com o Programa Estadual de Microbacias Hidrográficas (PEMBH) (Casa da Agricultura de Regente Feijó e Escritório de Desenvolvimento Rural de Presidente Prudente). Quanto à ocupação da área, foram encontradas culturas de café, milho, feijão, cana-de-açúcar, pêra, havendo o predomínio de pastagens. Os problemas associados ao manejo inadequado dos recursos naturais identificados foram: desestruturação do solo através da utilização do sistema convencional de plantio/semeadura, correção e adubação deficientes, compactação dos solos, pastagem degradada, presença de plantas daninhas, falta de manutenção ou ausência de práticas mecânicas de conservação, estradas mal locadas, erosões, área de preservação permanente com mata ciliar incompleta e reserva legal não averbada.... / The appropriate management of the soils and water is indispensable for the maintenance of the environmental quality and of life of the population. However, that is not happening in the Palmitalzinho river hydrography microbasin- Regente Feijó county- São Paulo state. The local presents several environmental problems, such as compacted soil and with low fertility, erosion and sedimentation of the courses of water. By the reason of this, this research has as objectives: to present the agricultural activities and their spacial disposition in the Palmitalzinho river microbasin; to identify negative aspects related to the inadequate handling of natural resources; to propose conservation practices and management of the resources soil and water; and to present the activities developed by Programa Estadual de Microbacias Hidrográficas (PEMBH). Properties were traveled, as well as information were collected in public organs involved with PEMBH. The Palmitazinho river microbasin presents culture of coffee, corn, bean, sugar-cane, pear, having the predominance of pasture. The problems related to the inadequate management of the identified natural resources were: degradation of the soil through the use of the conventional system of tillage, low investment in fertilizers and limestone, compactation of the soils, pasture with low production of biomass, presence of harmful plants, maintenance lack or absence of terraces, dirt road with problems, erosions, area of permanent preservation with incomplete riparian forest and not protocoled legal reserves. The suggestions proposed include the use of the areas according to their use capacity, accomplishment of chemical analysis of the soil for correct use of fertilizers and limestone, descompactation of the soil, terracing and its maintenance, adaptation of dirt road,...(Complete abstract, click electronic address below).
78

Meio ambiente e agricultura na microbacia hidrográfica do Córrego Palmitalzinho - Regente Feijó/São Paulo /

Golla, Amarílis Rós. January 2006 (has links)
Orientador: Antônio Cezar Leal / Banca: Antônio Nivaldo Hespanhol / Banca: Andréia Cristina da Silva / Resumo: O manejo adequado de solos e água é imprescindível para a manutenção da qualidade ambiental e de vida da população. Entretanto, isso não vem ocorrendo na microbacia hidrográfica do córrego Palmitalzinho -Regente Feijó/São Paulo. Nessa área, são encontrados diversos problemas ambientais, tais como, baixa fertilidade e compactação do solo, erosão e assoreamento dos cursos d'água. Em função disto, neste trabalho teve-se como objetivos: levantar as atividades agropecuárias e sua disposição espacial na microbacia hidrográfica do córrego Palmitalzinho; identificar aspectos negativos associados ao manejo inadequado dos recursos naturais; propor práticas de conservação e manejo dos recursos solo e água e levantar as atividades desenvolvidas pelo Programa Estadual de Microbacias Hidrográficas. Para atingir os objetivos foram realizados levantamentos de campo em todas as propriedades, entrevistas com os proprietários/funcionários das mesmas, assim como coletas de dados e informações em órgãos públicos envolvidos com o Programa Estadual de Microbacias Hidrográficas (PEMBH) (Casa da Agricultura de Regente Feijó e Escritório de Desenvolvimento Rural de Presidente Prudente). Quanto à ocupação da área, foram encontradas culturas de café, milho, feijão, cana-de-açúcar, pêra, havendo o predomínio de pastagens. Os problemas associados ao manejo inadequado dos recursos naturais identificados foram: desestruturação do solo através da utilização do sistema convencional de plantio/semeadura, correção e adubação deficientes, compactação dos solos, pastagem degradada, presença de plantas daninhas, falta de manutenção ou ausência de práticas mecânicas de conservação, estradas mal locadas, erosões, área de preservação permanente com mata ciliar incompleta e reserva legal não averbada...(Resumo completo, clicar acesso eletrônico abaixo). / Abstract: The appropriate management of the soils and water is indispensable for the maintenance of the environmental quality and of life of the population. However, that is not happening in the Palmitalzinho river hydrography microbasin- Regente Feijó county- São Paulo state. The local presents several environmental problems, such as compacted soil and with low fertility, erosion and sedimentation of the courses of water. By the reason of this, this research has as objectives: to present the agricultural activities and their spacial disposition in the Palmitalzinho river microbasin; to identify negative aspects related to the inadequate handling of natural resources; to propose conservation practices and management of the resources soil and water; and to present the activities developed by "Programa Estadual de Microbacias Hidrográficas" (PEMBH). Properties were traveled, as well as information were collected in public organs involved with PEMBH. The Palmitazinho river microbasin presents culture of coffee, corn, bean, sugar-cane, pear, having the predominance of pasture. The problems related to the inadequate management of the identified natural resources were: degradation of the soil through the use of the conventional system of tillage, low investment in fertilizers and limestone, compactation of the soils, pasture with low production of biomass, presence of harmful plants, maintenance lack or absence of terraces, dirt road with problems, erosions, area of permanent preservation with incomplete riparian forest and not protocoled legal reserves. The suggestions proposed include the use of the areas according to their use capacity, accomplishment of chemical analysis of the soil for correct use of fertilizers and limestone, descompactation of the soil, terracing and its maintenance, adaptation of dirt road,...(Complete abstract, click electronic address below). / Mestre
79

Fragilidade hídrica e ecodinâmica na bacia hidrográfica do rio Sergipe : desafios à gestão das águas

Silva, Luiz Carlos Sousa 14 March 2014 (has links)
The river basin as a geo-environmental unit of study is an important scenario for the knowledge of the functioning of the natural resources and consequent efficient and balanced planning of its usage, in order to adapting to the particular characteristics and capabilities of each environment. The Sergipe River Basin (SRB), for its peculiarities and economic, social and cultural importance to the State of Sergipe, was chosen as stage for our analysis focused on an integrated study that provides reliable subsidies for the elaboration of conservation policies and better use of the natural resources, more precisely, water. Being one of the most anthropized of the State because in its area there are important cities from an economic and population point of view, e.g. Aracaju, Nossa Senhora do Socorro, Itabaiana and Nossa Senhora da Glória, the study of the SRB, under the perspective proposed in this work, aims to bring contributions that may serve as a basis for further studies. The objective of this work is to analyze the ecodynamic water fragility in physiographic environments of the Sergipe River Basin, through assessing its water potential, conflicts generated from the multiple uses of water and the management model established by the Water Law. The methodological approach chosen for the analysis was based on the literature review of authors who treat the theme in question, by assessing, through the geo-environmental frailty model, which was developed by Ross (1994), the conditions of fragility of the basin. Previous researches have indicated that the Sergipe River Basin presents intense geo-environmental fragility, with its soils, waters, vegetation coverage and micro climates in constant exposure to the ecodynamics instability conditions caused by anthropic actions everywhere at the SRB, mainly due to the way of ownership and use of natural areas and water resources. The different geo-environmental peculiarities in each section of the BHS suggest different results of ecodynamic potential fragility and ecodynamic emerging fragility, thus contributing to the ecodynamic water weakness in the SRB ecodynamics with strong evidences of shortage and dependence of water from other water basins. This fragility on the water environment is governed by the model of use and occupation of soil in the twenty-six counties of the SRB. This finding reinforces the thesis that, by the peculiar and particular characteristics of each physiographic environment present in the Sergipe River Basin, the change and the adequacy of current management model need to be, urgently, implemented to answer the individual characteristics of each environments that make up the water basin of the Sergipe river, to strengthen the management of water resources and ensure water, quality and quantitatively, throughout the Sergipe River Basin to the multiple uses of present and future generations. / A bacia hidrográfica como unidade de estudo geoambiental é um importante cenário para o conhecimento do funcionamento dos recursos naturais e consequente planejamento eficaz e equilibrado de sua utilização, de modo a adequar-se às potencialidades e características peculiares de cada ambiente. A Bacia Hidrográfica do Rio Sergipe (BHS), por suas peculiaridades e importância econômica, social e cultural para o Estado de Sergipe, foi escolhida como palco para nossas análises focadas num estudo integrado que forneça subsídios confiáveis à elaboração de políticas de conservação e melhor utilização dos recursos naturais, mais especificamente, a água. Por ser uma das mais antropizadas do Estado, em consequência de em sua área estarem contidos importantes municípios do ponto de vista econômico e populacional, a exemplo de Aracaju, Nossa Senhora do Socorro, Itabaiana e Nossa Senhora da Glória, o estudo da BHS, sob a perspectiva proposta neste trabalho, deseja trazer contribuições que possam servir de base para outros estudos. O objetivo deste trabalho é analisar a fragilidade hídrica ecodinâmica nos ambientes fisiográficos da Bacia Hidrográfica do Rio Sergipe, avaliando sua potencialidade hídrica, os conflitos gerados a partir dos múltiplos usos da água e o modelo de gestão estabelecido pela Lei das Águas. O caminho metodológico escolhido para as análises pautou-se na revisão bibliográfica de autores que tratam das temáticas em questão, avaliando através do modelo de fragilidade geoambiental, elaborado por Ross (1994), as condições de fragilidade da bacia. Os estudos realizados indicam que a Bacia Hidrográfica do Rio Sergipe apresenta intensa fragilidade geoambiental, estando seus solos, águas, cobertura vegetal e micro climas em constante exposição às condições de instabilidade ecodinâmica, provocadas pelas ações antrópicas em toda área da BHS, principalmente devido à forma de apropriação e utilização dos espaços naturais e dos recursos hídricos. As diferentes peculiaridades geoambientais existentes em cada seção da BHS apontam para resultados distintos de fragilidade potencial ecodinâmica e de fragilidade emergente ecodinâmica, contribuindo assim para a fragilidade hídrica ecodinâmica na BHS com fortes indícios de escassez e dependência de águas de outras bacias hidrográficas. Essa fragilidade no ambiente hídrico é regida pelo modelo de uso e ocupação do solo nos vinte e seis municípios da BHS. Esta constatação reforça a tese de que, pelas características peculiares e particulares de cada ambiente fisiográfico presente na Bacia Hidrográfica do Rio Sergipe, a alteração e a adequação do atual modelo de gestão precisam ser, urgentemente, implementados para que atenda às características individuais de cada um dos ambientes que compõem a Bacia Hidrográfica do Rio Sergipe, no sentido de fortalecer a gestão dos recursos hídricos e garantir água, qualitativa e quantitativamente, em toda Bacia Hidrográfica do Rio Sergipe para os múltiplos usos da atual e das futuras gerações.
80

Dynamics of the British Ice Sheet and prevailing hydrographic conditions for the last 175,000 years : an investigation of marine sediment core MD04-2822 from the Rockall Trough

Hibbert, Fiona Danielle January 2011 (has links)
This study presents a stratigraphic investigation of the marine sediment core MD04-2822 from the Rockall Trough (56° 50.54' N, 11° 22.96' W; 2344 m water depth). This core is currently the only available high resolution record for the calibration of Late Quaternary sedimentary sequences of the British (Hebridean) margin. It therefore offers an unprecedented archive of changing sedimentological and climatological conditions for the last 175,000 years. The high resolution, multi-proxy records have enabled surface and deep water conditions within the Rockall Trough to be reconstructed. In addition, the fluctuating nature of ice-rafted debris (IRD) inputs to the MD04-2822 site allows a first order attempt of BIS dynamics for the entirety of the last glacial period (i.e. from the demise of the last interglacial to the decay of the Devensian/Weichselian ice sheet) as well as the majority of the penultimate (Saalian/MIS 6) glaciation. Sediment core MD04-2822 is ideally located to capture the dynamics of the British Ice Sheet (BIS) via a continuous record of IRD and fine-grained terrigenous inputs. Fundamental to this is the construction of a robust chronology. This was achieved via: the correlation of the benthic δ¹⁸O record to a global δ¹⁸O stack (SPECMAP); the correlation of the surface proxies (% N. pachyderma (sinistral) and XRF Ca) to the Greenland δ¹⁸O and Antarctic methane ice core records; and radiocarbon dating. This chronology was validated using both radiocarbon dating and tephra horizons. An evaluation of the event stratigraphy approach used in the construction of the MD04-2822 chronology is presented. The marine record provides a valuable archive of past ice sheet dynamics as much terrestrial evidence is removed or obscured by subsequent ice sheet oscillations MD04-2822 provides the first evidence for the expansion of the BIS onto the Hebridean Margin during MIS6 (thereby confirming previous long-range seismic correlations). The continuous sedimentation at MD04-2822 enabled the first insights into the early dynamics of the last BIS. Increases in IRD and fine grained terrigenous material delivered to the MD04-2822 at ca. 72 kyr represent the first significant delivery of material from the BIS across the continental shelf to the core site. The BIS would therefore have attained a marine calving margin by this time. A multi-proxy investigation of provenance was undertaken, however unequivocal provenance determinations remain problematic. The location of the core suggest the proximal BIS as the most likely source of terrigenous inputs. The expanded nature of the MD04-2822 sediments during the penultimate deglacial (Termination II) provides the first details of BIS dynamics for this period: the interplay of large inputs of freshwater from the decay of the Saalian (MIS 6) ice sheets (including the BIS) upon the surface and deep water circulation of the North Atlantic is investigated. In addition, sub-orbital climatic variability is documented at this location throughout the last interglacial (MIS 5e) and appears to be an intrinsic feature of both the N.E. Atlantic surface and deep water circulation of the last 175 kyr.

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