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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.
21

Modelling of ocean tides

Das, Pritha, School of Methematics, UNSW January 1998 (has links)
In this thesis three independent studies of tidal dynamics have been pesented. The first is an analytical study of continental shelf tides forced at the ocean boundary. Earlier studies have shown that the response for a sloping shelf and a flat shelf differ and that the response for a flat shelf changes when tides are incident at an angle. Other studies considered a sloping shelf but they did not take into account a possible non-zero depth at a coastal wall. This study shows that the effects of a sloping shelf, a coastal wall and obliquely incident tides an all significantly modify the response on the shelf. The modification increases with the width of the shelf, and in a wide shelf scenario, near resonance, it greatly modifies the response. Secondly, the Princeton Ocean Model in barotropic mode along with a tracer transport module has been used to study the tides of Sydney Harbour. The tidally induced residual circulation due to the semi-diurnal tide consists of a series of recirculating gyres which are due to the interaction of flow with topography. This study shows that in the harbour it is the Lagrangian residual velocity not the Eulerian residual velocity which determines the net transport of material over a tidal cycle. In addition, the flushing time of the harbour varies significantly in space, and the tidal mixing is restricted in the vicinity of the entrance. The third is a theoretical study of forced oscillations in a rotating, flat-bottomed, circular basin. This study shows that the direction of propagation of waves in a basin depends on the ratio of its radius to depth. At each latitude there is a critical value of this ratio and this value decreases with increase in latitude. Beyond this value, waves start to propagate around the basin in the opposite direction to the earth ???s rotation (clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere).The presence of friction increases this critical value which shows that friction plays an important role in determining the response.
22

Modelling of ocean tides

Das, Pritha, School of Methematics, UNSW January 1998 (has links)
In this thesis three independent studies of tidal dynamics have been pesented. The first is an analytical study of continental shelf tides forced at the ocean boundary. Earlier studies have shown that the response for a sloping shelf and a flat shelf differ and that the response for a flat shelf changes when tides are incident at an angle. Other studies considered a sloping shelf but they did not take into account a possible non-zero depth at a coastal wall. This study shows that the effects of a sloping shelf, a coastal wall and obliquely incident tides an all significantly modify the response on the shelf. The modification increases with the width of the shelf, and in a wide shelf scenario, near resonance, it greatly modifies the response. Secondly, the Princeton Ocean Model in barotropic mode along with a tracer transport module has been used to study the tides of Sydney Harbour. The tidally induced residual circulation due to the semi-diurnal tide consists of a series of recirculating gyres which are due to the interaction of flow with topography. This study shows that in the harbour it is the Lagrangian residual velocity not the Eulerian residual velocity which determines the net transport of material over a tidal cycle. In addition, the flushing time of the harbour varies significantly in space, and the tidal mixing is restricted in the vicinity of the entrance. The third is a theoretical study of forced oscillations in a rotating, flat-bottomed, circular basin. This study shows that the direction of propagation of waves in a basin depends on the ratio of its radius to depth. At each latitude there is a critical value of this ratio and this value decreases with increase in latitude. Beyond this value, waves start to propagate around the basin in the opposite direction to the earth ???s rotation (clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere).The presence of friction increases this critical value which shows that friction plays an important role in determining the response.
23

Modelling of ocean tides

Das, Pritha, School of Methematics, UNSW January 1998 (has links)
In this thesis three independent studies of tidal dynamics have been pesented. The first is an analytical study of continental shelf tides forced at the ocean boundary. Earlier studies have shown that the response for a sloping shelf and a flat shelf differ and that the response for a flat shelf changes when tides are incident at an angle. Other studies considered a sloping shelf but they did not take into account a possible non-zero depth at a coastal wall. This study shows that the effects of a sloping shelf, a coastal wall and obliquely incident tides an all significantly modify the response on the shelf. The modification increases with the width of the shelf, and in a wide shelf scenario, near resonance, it greatly modifies the response. Secondly, the Princeton Ocean Model in barotropic mode along with a tracer transport module has been used to study the tides of Sydney Harbour. The tidally induced residual circulation due to the semi-diurnal tide consists of a series of recirculating gyres which are due to the interaction of flow with topography. This study shows that in the harbour it is the Lagrangian residual velocity not the Eulerian residual velocity which determines the net transport of material over a tidal cycle. In addition, the flushing time of the harbour varies significantly in space, and the tidal mixing is restricted in the vicinity of the entrance. The third is a theoretical study of forced oscillations in a rotating, flat-bottomed, circular basin. This study shows that the direction of propagation of waves in a basin depends on the ratio of its radius to depth. At each latitude there is a critical value of this ratio and this value decreases with increase in latitude. Beyond this value, waves start to propagate around the basin in the opposite direction to the earth ???s rotation (clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere).The presence of friction increases this critical value which shows that friction plays an important role in determining the response.
24

Protecting the Diversity of the Depths: Strengthening the International Law Framework

Warner, Robin Margaret Fraser January 2006 (has links)
Doctor of Philosophy(PhD) / It is only in recent decades that marine scientific research has begun to reveal the true physical characteristics and resource potential of the open ocean and deep seabed beyond national jurisdiction. A combination of factors such as the depletion of inshore fish stocks and an increase in global maritime trade has led to greater usage of the vast maritime area beyond the territorial sea and exclusive economic zone limits of the coastal states. Human activities in this area of the ocean, which covers approximately 50% of the world’s surface, have expanded to include bioprospecting, exploration for deep seabed minerals, more sophisticated marine scientific research and deep sea tourism. This rise in human activities beyond the offshore zones of coastal states poses actual and potential threats to the physical characteristics and biodiversity of the open ocean and deep sea environments. Arbitrary human intrusions into this largely unexplored marine domain have the potential to harm the intricate links between complex marine ecosystems and to erode components of marine biodiversity. This thesis examines the global and regional provisions which have been put in place to regulate the environmental impacts of human activities that occur beyond national jurisdiction. An analysis of these instruments and their implementation reveals that the current international law framework provides only minimal levels of protection for the marine environment beyond national jurisdiction. It explores several options based on the 1982 United Nations Convention on the Law of the Sea (LOSC) and the 1992 Convention on Biological Diversity (CBD) to establish a cohesive environmental protection system for the marine environment beyond national jurisdiction.
25

EFFECT OF SURFACE-MANTLE WATER EXCHANGE PARAMETERIZATIONS ON EXOPLANET OCEAN DEPTHS

Komacek, Thaddeus D., Abbot, Dorian S. 16 November 2016 (has links)
Terrestrial exoplanets in the canonical habitable zone may have a variety of initial water fractions due to random volatile delivery by planetesimals. If the total planetary water complement is high, the entire surface may be covered in water, forming a "waterworld." On a planet with active tectonics, competing mechanisms act to regulate the abundance of water on the surface by determining the partitioning of water between interior and surface. Here we explore how the incorporation of different mechanisms for the degassing and regassing of water changes the volatile evolution of a planet. For all of the models considered, volatile cycling reaches an approximate steady state after similar to 2 Gyr. Using these steady. states, we find that if volatile cycling is either solely dependent on temperature or seafloor pressure, exoplanets require a high abundance (greater than or similar to 0.3% of total mass) of water to have fully inundated surfaces. However, if degassing is more dependent on seafloor pressure and regassing mainly dependent on mantle temperature, the degassing rate is relatively large at late times and a steady. state between degassing and regassing is reached with a substantial surface water fraction. If this hybrid model is physical, super-Earths with a total water fraction similar to that of the Earth can become waterworlds. As a result, further understanding of the processes that drive volatile cycling on terrestrial planets is needed to determine the water fraction at which they are likely to become waterworlds.
26

Patrons de biodiversité a` l'échelle globale chez les dinoflagellés planctoniques marins / Patterns of biodiversity on a global scale in marine planktonic dinoflagellates

Le Bescot, Noan 10 March 2014 (has links)
Les dinoflagellés forment un groupe complexe de protistes avec une grande diversité de morphologies, physiologies, et cycles de vies qui leur confèrent une forte capacité d'adaptation à l'ensemble des milieux (marins et dulçaquicoles) et habitats (pélagiques et benthiques) aquatiques rendant difficile l¿étude de leur diversité et de leur écologie. L'objectif de cette thèse a été la recherche de patrons globaux de biodiversité et de structuration des communautés de dinoflagellés pélagiques marins à l'échelle planétaire. Un protocole d'échantillonnage morphogénétique, couvrant la totalité de leur spectre de taille et une partie importante de leurs variabilités spatio-temporelles, a été développé (Tara-Oceans). Divers outils d'acquisition automatique à haut débit des données ont été testés. La diversité, l'abondance relative et la distribution géographique des espèces du genre Neoceratium ont été évaluées en mer Méditerranée par FlowCAM. Une étude de la structuration de la biodiversité a été réalisée par metabarcoding de l¿ADNr 18S (fragment V9). La construction d'une base de séquences ADNr de référence (DinR2) a permis l¿assignation taxonomique des metabarcodes environnementaux. L¿approche par metabarcode révèle une diversité remarquable et insoupçonnée des pico-dinoflagellés (<5µm) et que, indépendamment de l'écosystème étudié et de la période d'échantillonnage, l¿abondance des différents ordres dépend essentiellement de la taille (pico-, nano-, micro-, et meso-plancton). La structuration des communautés de dinoflagellés de différentes fractions de tailles de la zone photique a été confrontée à certains facteurs environnementaux ouvrant des pistes de recherche prometteuses / Dinoflagellates form a complex group of protists with a variety of morphologies, physiologies, and life cycles that give them a strong adaptation to all aquatic environments (marine and freshwater) and habitats (pelagic and benthic) making difficult to study their diversity and ecology. The objective of this thesis was the search for global biodiversity patterns and community structure of marine pelagic dinoflagellates across the world?s oceans. A morphogenetic sampling protocol, covering the entire spectrum of their size and an important part of their spatio-temporal variability, was developed (Tara-Oceans). Various tools for an automatic acquisition broadband data were tested. Diversity, relative abundance and geographical distribution of the genus Neoceratium were evaluated by FlowCAM in Mediterranean Sea. A study of the structure of biodiversity was conducted by metabarcoding with 18S rDNA (V9 fragment). Building a base of rDNA reference sequences (DinR2) allowed the taxonomic assignment of environmental metabarcodes. The metabarcode approach reveals a remarkable and unexpected diversity of pico-dinoflagellates (<5?m) and, regardless of the studied ecosystem and the sampling period, that abundance of different levels mainly depends to the size fractions (pico-, nano-, micro- and meso- plankton). Structuring of dinoflagellates communities in different size fractions of the photic zone was facing to some environmental factors and opens promising avenues for research
27

From Washington Consensus To Global Crisis

Mutlu, Inan 01 September 2010 (has links) (PDF)
This thesis focuses on the changing modes of state intervention into the economy in neoliberalism. It contends that the so called free market is neither a natural process nor an inevitable result of the harmony of interest, but the result of a deliberate political making process. The global economic crisis provided ample evidence to refute the claim that state and market are separately existing and antagonistic entities and indicates that the issue is not the market or the state, since the state in a capitalist society is equally subordinate to capital, simply providing an alternative mode of regulation of capital accumulation. The state has always been essential for &quot / proper&quot / workings of the market, especially for the interests of capital and the neoliberal state is not an exception
28

The Geographies of Policy: Assembling National Marine Aquaculture Policy in the United States

Fairbanks, Luke W. January 2015 (has links)
<p>In the United States, marine aquaculture is increasingly viewed as way to offset stagnating wild fisheries production, help faltering coastal community economies, and address a growing national seafood trade deficit. The national government has outwardly supported the development of the sector through policies, plans, and other statements. However, many social and environmental questions surround prospective expansion, and actual policy development and implementation has been slow. This dissertation builds on recent work in human geography and policy studies to explore US national marine aquaculture policy processes, conceptualizing policy as a dynamic assemblage of actors, spaces, practices, and relations. It contributes to our understanding of oceans geography and policy processes by addressing three questions: (1) How do actors interact within the assemblage negotiate, construct, and develop national policies? (2) What practices are actors employing to shape aquaculture policymaking, and what views underlie them? (3) What are the practical, and often local, implications of these processes, and how do actors interact with and within policy development (or not)?</p><p>These questions are approached empirically by tracing the US national marine aquaculture policy assemblage across time, space, and scale. The dissertation draws on research conducted within and outside the US government, focusing on the internal practices of the state and the National Oceanic and Atmospheric Administration (NOAA), as well as a case of local and regional policy implementation and development in New England. It also focuses on offshore aquaculture policy, as well as marine aquaculture more generally. The dissertation uses discourse analysis, ethnography, and other approaches to conduct a geographic policy analysis that explores the processes and relationships producing national marine aquaculture policy in the United States.</p><p>Overall, this research shows that broad or monolithic conceptualization of the state, its motivations, its practices, and their implications are oversimplified. The federal government features a diversity of actors, discourses, and ideas about marine aquaculture and its policy development, which manifest in different paths to reform and conflicting efforts within the state itself. Further, national policy processes are not contained within the national government, but are co-produced by mobile and dynamic actors and policies across contexts. Actors deploy particular discourses about marine aquaculture’s risks and opportunities, government agencies and offices claim and reclaim authority over the sector, bureaucrats engage in diverse everyday policy practices and interactions, and policy ideas and policies themselves change as they are translated and deployed in new spaces and by different actors. Together, these processes suggest that rather than expecting a totalizing form of marine aquaculture development in the United State, it is important to consider the ruptures and opportunities within the assemblage that might allow for alternative forms of policy, coordination, and implementation at all scales.</p> / Dissertation
29

Organohalogen environmental pollutants in Baltic fish : chemical characterization and toxicological evaluation with a focus on bone disturbances /

Stern, Natalia, January 2005 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.
30

The Predictive Power of Commercial Fisheries Stock Assessments

Docking, Kathryn A 12 September 2018 (has links)
Organizations responsible for managing commercial fisheries conduct annual stock assessments to monitor stock and, in principle, reduce the risk of overexploitation. These are fundamental to setting the total allowable catch for the upcoming fishing year. While there have been many attempts to estimate uncertainty associated with certain components and estimates of stock assessments, to date there has been no systematic assessment of their forecasted predicted value. Using data from annual stock assessments from 65 commercial fisheries around the world, estimates were obtained of both predicted (from the previous year) and observed (in the current year) catch-at-age. When comparing observed (actual) and predicted catch-at-age for a given stock, estimates were obtained of the predictive power of next-season forecasts. Using other attributes of the fishery and the stock (biological (e.g. life history) and management (e.g. assessment model employed)), empirical models were constructed that attempt to determine variability in predictive power among stocks. It was observed that, on average, within-year predictive powers (age-series within time samples) were higher than year over year predictive powers (time-series within age samples). While focusing on time-series within age, it was observed that change over the period of record (in natural mortality rate, assessment model employed, etc.) reduced predictive power; while for age-series within time, it was shown that cumulative landings reduced predictive power. This study represents one of the first attempts to quantify systematically the predictive power of fisheries stock assessment models.

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