Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2006. / Includes bibliographical references (p. 139-143). / The continuous supply of heat and fresh water from the boundaries to the interior of the Labrador Sea plays an important role for the dynamics of the region and in particular, for the Labrador Sea Water formation. Thus, it is necessary to understand the factors governing the exchange of properties between the boundary and interior. A significant fraction of heat and fresh water, needed to balance the annual heat loss and to contribute to the seasonal freshening of the Labrador Sea, is thought to be provided by coherent long-lived anticyclonic eddies shed by the Irminger Current. The population, some properties, rates and direction of propagation of these anomalies are known but the evolution and the mechanism of their decay are still far from obvious. In this work I investigated their water mass properties and evolution under the strong wintertime forcing using hydrographic data from 1990-2004 and a 1-dimensional mixed layer model. There were 50 eddies found in the hydrographic data record, 48 of which were identified as anticyclones. Vertical structure of the eddies was investigated, leading to the categorization of all the anticyclones into three classes: 12 - with a fresh surface layer and no mixed layer, 18 - without a fresh layer and at least one mixed layer, and 18 with ambiguous vertical structure. Four eddies of the second group appeared to have cores extending to as deep as 1500 m vertically and an isopycnal displacement of 400-600 m. A number of eddies without a fresh water cap contained Labrador Sea Water from the previous year at mid-depths. / (cont.) Vertical structure of the eddies was investigated, leading to the categorization of all the anticyclones into three classes: 12 - with a fresh surface layer and no mixed layer, 18 - without a fresh layer and at least one mixed layer, and 18 with ambiguous vertical structure. Four eddies of the second group appeared to have cores extending to as deep as 1500 m vertically and an isopycnal displacement of 400-600 m. A number of eddies without a fresh water cap contained Labrador Sea Water from the previous year at mid-depths. / by Tatiana Rykova. / S.M.

Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2006. / Includes bibliographical references (p. 81-86). / The impact of the Greenland tip jet on the wintertime mixed-layer of the southwest Irminger Sea is investigated using in-situ moored profiler data and a variety of atmospheric data sets. The mixed-layer was observed to reach 400 m in the spring of 2003, and 300 m in the spring of 2004. Both of these winters were mild and characterized by a low North Atlantic Oscillation (NAO) index. All of the storms that were advected through the region were tracked, and the tip jet events that occurred throughout the two winters were identified. Composite images of the tip jets elucidated the conditions during which tip jets were likely to take place, which led to an objective method of determining tip jet occurrences by taking into account the large-scale pressure gradients. Output from a trajectory model indicates that the air parcels entering a tip jet accelerate and descend as they are deflected around southern Greenland. A heat flux timeseries for the mooring site was constructed that includes the enhancing influence of the tip jet events. This was used to drive a one-dimensional mixed-layer model, which was able to reproduce the observed mixed-layer deepening in both winters. All of the highest heat flux events took place during tip jets, and removal of the tip jets from the heat flux timeseries demonstrated their importance in driving convection east of Greenland. / (cont.) The deeper mixed-layer of the first winter was in large part due to a higher number of robust tip jet events, which in turn was caused by a greater number of storms passing northeast of southern Greenland. This interannual change in storm tracks was attributable to a difference in upper level steering currents. Application of the mixed-layer model to the winter of 1994-1995, during a period characterized by a high NAO index, resulted in convection reaching 1600 m. This prediction is consistent with concurrent hydrographic data, supporting the notion that deep convection can occur in the Irminger Sea during strong winters. / by Kjetil Våge. / S.M.

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. / "June 2010." Cataloged from PDF version of thesis. / Includes bibliographical references (p. 151-159). / The Labrador Sea, as one of a few places of deep water formation, plays an important role in the Meridional Overturning Circulation. While the interior of the Labrador Sea, where the deepest convection takes place, is known to experience variability on time scales ranging from days to decades, little is known about the variability of the other components of the Labrador Sea circulation - the boundary current system and the eddies that connect it with the interior. Using various types of in situ data combined with the surface flux and satellite altimetry data products, I studied the variability of both the boundary current system and the eddies on different time scales as well as their influence on the post-convective re-stratification of the Labrador Sea interior. The analysis presented in the thesis supports the result of the previous theoretical studies that argue that lateral fluxes, driven by the boundary current/interior gradients, play an important role in the post-convective restratification of the Labrador Sea. I found that both components of the boundary current, the surface West Greenland Current and the subsurface Irminger Current, have a strong seasonal cycle. In the spring both the West Greenland and Irminger Currents are colder and fresher than in the fall. However, the West Greenland Current is faster and thicker in the spring while the Irminger Current is the fastest and thickest in the fall. My analysis suggests that the observed seasonal changes in the velocity are primarily due to the baroclinic component of the current while the barotropic component remains nearly unchanged. The Subpolar Gyre, and the Labrador Sea in particular, have experienced a decline in the circulation accompanied by the warming of the water column over the last decades. I found that a similar trend is seen in the West Greenland Current system which slowed down from 1992 to 2004, primarily due to a decrease in the barotropic flow. At the same time, the subsurface Irminger Current has become warmer, saltier, and lighter, something that is also reflected in the properties of the eddies. Two years exhibited pronounced anomalies: in 1997 and 2003 the velocity, temperature and salinity of the Irminger Current abruptly increase with respect to the overall trend. Finally, I discuss the impacts of the boundary current changes on the lateral fluxes that are responsible for the restratification of the Labrador Sea and the properties of the interior. / by Tatiana Rykova. / Ph.D.

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)

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.

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.

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.

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

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)

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).