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Tesi sul tema "Oceans"
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1
King, B. A. "Loquency waves in equatorial oceans". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373656.
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2
Cullum, Jodie. "Modelling studies of exoplanetary oceans". Thesis, University of East Anglia, 2018. https://ueaeprints.uea.ac.uk/67833/.
Testo completoAbstract (sommario):
The ocean plays a key role in the climate of Earth, and it is therefore expected that any oceans present on an exoplanet would also be a crucial component of the climate system and hence have implications for the habitability of the planet. However, many planetary and oceanic properties cannot be assumed to be the same on an exoplanet as on Earth, and therefore the behaviour of the ocean cannot be assumed. Here, basic land configurations are explored and a single meridional barrier is used throughout the other experiments, as this is the simplest configuration of any substantial land mass. The effect of ocean salinity, at a level both higher and lower than on Earth, is explored for the first time and reversal of the Earth-like meridional overturning circulation is found. The proportionality between mean salinity and salinity gradients in the ocean is established. The impact of planetary rotation period is also investigated, and it is concluded that a longer rotation period results in a greater poleward ocean heat transport, with the additional novel conclusions of a shallower thermocline depth, increased horizontal ocean velocities, and stronger overturning circulation. Finally, existing ocean modelling of a tidally locked configuration is furthered by the addition of different land masses, the extent of the zonal circulation and magnitude of the zonal heat transport is found to have significant dependence on the location of a meridional barrier in the ocean, with resulting dark side mean temperatures varying by over 7 ̋C. The modelling presented here highlights the importance of the consideration of the ocean in exoplanetary climate studies, and its role in planetary habitability.
3
Winterbourne, Jeffrey Richard. "Dynamic topography in the oceans". Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610506.
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4
Šimek, Bohuslav. "Vývoj konceptu strategie "Modrých oceánů"". Master's thesis, Vysoká škola ekonomická v Praze, 2013. http://www.nusl.cz/ntk/nusl-165092.
Testo completoAbstract (sommario):
The strategic concept of "blue oceans" is currently undoubtedly one of the most interesting and most often talked strategic concepts. The thesis is therefore deals with the development of this strategic concept at the time and on the basis of previous papers of the authors in which were introduced tools and frameworks that later became part of the blue ocean strategy concept. The thesis also deals with other publications that the idea of the concept uses in own frames or in some way continues to build upon it. Further a description of the whole strategic concept is presented with each of analytical framework and tool with emphasis on additional context and findings of the section on the recent development of the concept. A key part of the thesis is the application of the concept to the three services - Knihovnička.cz Prezi and the Steam and evavulation of these tools with emphasis to the conclusions that have been made in the recent development of the strategic concept of "blue oceans" and its application.
5
Wood, R. G. "Rossby waves in mid-latitude oceans". Thesis, University of Essex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379474.
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6
Harpole, Alice. "Multiscale modelling of neutron star oceans". Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/422175/.
Testo completoAbstract (sommario):
Type I X-ray bursts are thermonuclear burning events which occur on the surface of accreting neutron stars. Burning begins in a localised spot in the star’s ocean layer before spreading across the entire surface. By gaining a better understanding of X-ray bursts, tighter limits can be determined for other neutron star properties such as the mass, radius, spin frequency and magnetic field. The ocean environment is very extreme, involving much higher pressure, temperature and magnetic field strength compared to the conditions typically found in terrestrial systems. We shall be looking at the effects of the strong gravitational field, modelling the ocean using general relativistic hydrodynamics. The physics of X-ray bursts acts over a wide range of scales, which introduces a number of challenges when modelling them. In this work, we use the multiscale approach to couple together multiple physical models in order to best capture the physics across these various scales. On the smallest scales, the physics is dominated by turbulent burning. The speed of propagation of the burning front is much slower than the acoustic speed, making it difficult to model this with conventional numerical schemes. We therefore instead use the low Mach number approximation, which we have derived and implemented for the relativistic fluid equations based on the existing approach developed for the Newtonian case. On larger scales, the burning front can be thought of as a discontinuity. To model this, we investigate the reactive Riemann problem for relativistic deflagrations and detonations and develop a numerical solver. The large scale propagation of the burning front is believed to be dominated by the Coriolis force. To capture this behaviour, we have derived and implemented a model for the relativistic form of the shallow water equations. Finally, we construct a hybrid scheme to combine the best features of these approximations, extending existing adaptive mesh refinement techniques to include different physical models at different scales.
7
Xue, Zichen. "Cadmium isotope variations in the oceans". Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/10547.
Testo completoAbstract (sommario):
A number of previous studies have identified considerable mass dependent variations in the Cd isotope compositions of both terrestrial and extraterrestrial samples. On Earth, stable isotope effects for Cd are particularly prominent in the oceans, and the largest natural terrestrial Cd isotope fractionations of about 4‰ have been reported for Cd-depleted surface seawater. These effects have generally been attributed to reflect isotope fractionation of Cd that occurs during biological uptake and utilization of dissolved seawater Cd. This finding confirms studies, which identified Cd as an essential marine micronutrient. This was first inferred from the phosphate-like distribution of the metal in the oceans and more recently demonstrated by work, which confirmed that Cd can act as catalytic metal ion in carbonic anhydrase, an enzyme which plays a central role in inorganic carbon acquisition of phytoplankton in the oceans. The marine Cd isotope fractionations are thus of interest, as they can be used to study the cycling of the micronutrient Cd as well as its impact on ocean productivity and the global carbon cycle. As part of this PhD project, I have developed a new procedure for Cd isotope analyses of seawater, which is suitable for samples as large as 20 L and Cd concentrations as low as 1 pmol/L. The procedure involves use of a 111Cd-113Cd double spike, co-precipitation of Cd from seawater with Al(OH)3 Cd purification by column chromatography, and subsequent isotope analysis by MC-ICP-MS (multiple collector inductively coupled plasma mass spectrometry). The methodology can routinely provide є114=110Cd data with a precision of about ± 0:5є (2sd) when at least 20-30 ng of natural Cd are available for analysis. However, even seawater samples with Cd contents of only 1-3 ng can be analysed with a reproducibility of about ±3 to ± 5є. The new methodology was applied to investigate Cd isotope variations in about 150 seawater samples from the North Atlantic Ocean, the Southern Ocean HNLC (high nutrient low chlorophyll) region, and the Peruvian oxygen minimum zone in the Eastern Pacific Ocean. The samples exhibited variable but highly systematic Cd isotope variations that were comprehensively interpreted in the context of previously published oceanographic and biogeochemical data.
8
Pabi, Sudeshna. "Carbon biogeochemistry in the polar oceans /". May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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9
Cheng, Sukun. "Wave-Ice Interaction in Polar Oceans". Thesis, Clarkson University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10785835.
Testo completoAbstract (sommario):
As the Arctic sea ice extent shrinks, it becomes feasible to navigate through the Arctic Ocean. The Arctic routes shorten the marine transport between the American and Asian-European continents. To enable navigation planning, reliable wave forecasts in the ice covered area is highly demanded. However, as one component of the ocean wave models, the wave-ice interaction modelling is still under development. To obtain good wave forecasts, the effect of all ice types on wave propagation must be modeled correctly.
This dissertation contributes to the wave-ice interaction modelling for general sea ice-covered waters. For this purpose, the research questions addressed include investigating a theoretical model that assumes ice covers as a continuous layer of viscoelastic material. The derived dispersion relation contains two parameters associated with the equivalent viscoelastic properties of different ice types. Implementation of this model in an operational ocean wave model is a numerical problem to solve. Parameters in this viscoelastic model require data calibration. Inverse methods are developed using measurements from a recent field campaign to establish a relation among ice types and these theoretical parameters.
Three main questions of this study are answered as the following. 1) To understand the physical nature of ice-water layered system in the viscoelastic model. The wave characteristics are compared with those from developed theories of wave propagation in other layered systems. It concludes that the roots of the dispersion relation are identified as the flexural gravity, pressure, shear, evanescent and Rayleigh-Lamb waves. A wave mode swap phenomenon is also discussed. 2) To solve the numerical issues in applying the model in a global ocean wave model WAVEWATCH III®. Strategies of determining the dominant wave mode and expediency of the numerical procedure are proposed. The updated ice source module for WAVEWATCH III ® performs better in accuracy, efficiency and robustness than its predecessor. 3) Inverse methods are applied to calibrate the model using data collected in the western Arctic Ocean, populated predominantly with pancake ice. The calibrated parameters can be used for wave forecasts in fields of the same ice type in the future. Furthermore, a combined laboratory and numerical study is conducted for wave propagating through an array of uniformed floes. The effective rigidity of the cover is explained by the change of elastic strain energy due to the free edges of each floe. An empirical relation is obtained for the effect rigidity in terms of the floe size and other length scales. This relation may be used to estimate the effective rigidity of an ice cover by in situ or remote sensing images. By answering the above questions, this dissertation contributes to the application of a viscoelastic model for wave hindcasts/forecasts in the whole ice-covered waters.
10
Sheard, John Daniel. "Acoustic wave propagation in ice covered oceans". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319827.
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11
Booth, Ben Berry Boyd. "The role of oceans in climate change". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413980.
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12
Radia, N. V. "Frazil ice formation in the polar oceans". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1419009/.
Testo completoAbstract (sommario):
Areas of open ocean within the sea ice cover, known as leads and polynyas, expose ocean water directly to the cold atmosphere. In winter, these are regions of high sea ice production, and they play an important role in the mass balance of sea ice and the salt budget of the ocean. Sea ice formation is a complex process that starts with frazil ice crystal formation in supercooled waters, which grow and precipitate to the ocean surface to form grease ice, which eventually consolidates and turns into a layer of solid sea ice. This thesis looks at all three phases, concentrating on the rst. Frazil ice comprises millimetre-sized crystals of ice that form in supercooled, turbulent water. They initially form through a process of seeding, and then grow and multiply through secondary nucleation, which is where smaller crystals break o from larger ones to create new nucleii for further growth. The increase in volume of frazil ice will continue to occur until there is no longer super-cooling in the water. The crystals eventually precipitate to the surface and pile up to form grease ice. The presence of grease ice at the ocean surface dampens the e ects of waves and turbulence, which allows them to consolidate into a solid layer of ice. The ice then mostly grows through congelation ice forming beneath the layer of ice. A mathematical model describing the above processes is formulated and used to simulate ice growth. The model consists of conservation equations for mass and heat, with an imposed momentum budget. Simulations are realistic and numerical sensitivity experiments are used to investigate the dependence of ice growth on the ambient environment.
13
Homoky, William Bela. "Iron inputs from sediments to the oceans". Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/169045/.
Testo completoAbstract (sommario):
This thesis explores the nature and ubiquity of iron (Fe) inputs from sediments to the oceans. In the last 10 years continental shelf sediments have become widely recognised as important vectors for dissolved Fe inputs to the oceans, where bacterial dissimilatory Fe-reduction (DIR) promotes the flux of Fe to the water column during the oxidation of sedimentary organic matter. Deep-sea and volcanogenic sediments however, are important reservoirs of Fe, which have not yet been investigated as sources of Fe to seawater. Furthermore knowledge of the nature of Fe phases involved in sediment, porefluid and seawater cycling is limited. The nature of Fe cycling was investigated in deep-sea volcaniclastic surface-sediments (0-20 cmbsf). Pore-fluid and sediment samples were collected from tephra-rich sites near the active volcanic island of Montserrat, Caribbean Sea, and mixed biosiliceous sites around the dormant Crozet Island archipelago, Southern Ocean. Analyses reveal both regions maintain high pore-fluid Fe concentrations close to the sediment surface (up to 20 μM 0-5 cmbsf), despite relatively low organic carbon supply and contrasting oxygen utilization pathways. The oxidation of young tephra is thought to maintain the steep oxygen gradient measured in Montserrat sediments, and is considered to be an important component of Fe, and in particular manganese (Mn), cycling with local bottom water. Unlike Montserrat dissolved Fe and Mn in Crozet pore-fluids are dominated by colloidal phases (0.02-0.2 μm), and in both oxic and sub-oxic sediment layers. Thus mixed biosiliceous-volcaniclastic sediments are shown to host important colloidal-Fe generating reactions, which it is argued, promote the exchange of Fe with the overlying bottom waters. Re-cycling processes close to the seafloor are likely to determine the impact of this flux on seawater Fe budgets. Low-cost ex-situ incubation experiments were used to measure a benthic Fe flux on sediments from the river-dominated Californian margin (6.3 ± 5.9 μmol Fe m-2 yr-1) consistent with previous studies. Fe and Mn fluxes from Montserrat tephra deposits were also assessed; Differences in oxidation kinetics are shown to prevent the accumulation of Fe, yet permit the accumulation of Mn (~27 μmol m-2 yr-1) in Montserrat bottom waters. Studies indicate temporospatial variations to bioirrigation and sediment re-suspension are important aspects of sedimentary Fe inputs that are poorly represented by conventional sampling methods. In an effort to trace the biogeochemical processing of pore-fluid Fe in Crozet sediments, its isotopic composition was determined, representing the first measurements of their kind in deep-sea pore-fluids. Unique relative to previous studies of pore-fluid Fe isotopes, the near-crustal δ56Fe compositions, demonstrate that DIR does not impart the same light Fe-isotopic signature that characterises previous sub-oxic pore-fluids. Comparison of reactive Fe contents between Crozet and pacific margin sediments indicates pore-fluid Fe isotopes reflect the extent to which Fe is recycled by redox processes. This discovery brings to light the potential for Fe isotopes to trace the input of Fe from shelf sediments, where redox re-cycling of Fe is extensive. The mean oceanic Fe isotope composition (δ56Fe) is predicted to be -0.1 to -3.2‰ depending on the balance of uncertainty in input terms. The predicted surface water Fe isotope composition in the Crozet region (-2.0 to - 2.2‰) is shown to reflect the light composition of shelf-derived Fe for a Fe inventory already constrained for this region.
14
Zhang, Yuan. "An observational study of atmosphere-ocean interactions in the northern oceans on interannual and interdecadal time-scale /". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/10038.
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15
Bennett, Sara L. "Where three oceans meet the Algulhas retroflection region /". Woods Hole, Mass. : Woods Hole Oceanographic Institution, 1988. http://catalog.hathitrust.org/api/volumes/oclc/19285078.html.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, 1988."Funding was provided by the Office of Naval Research through contract Numbers N00014-84-C-0134, N00014-85-C-0001, and N00014-87-K-0001." "October 1988." Includes bibliographical references (p. 357-367).
16
Haslett, Simon K. "Pliocene-Pleistocene radiolarian investigations of the Equatorial oceans". Thesis, University of South Wales, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265674.
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17
Bennett, Sara L. "Where three oceans meet : the Agulhas retroflection region". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/51466.
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18
Dusenberry, Jeffrey A. (Jeffrey Allen). "Picophytoplankton photoacclimation and mixing in the surface oceans". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/38740.
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McClelland, Harry-Luke Oliver. "Carbon dioxide and coccolithophore physiology in ancient oceans". Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:8a787b15-54cc-4a4e-8350-879a912cfe22.
Testo completoAbstract (sommario):
Coccolithophores form an important and dynamically evolving component of the carbon cycle. These ubiquitous single-celled marine calcifying phytoplankton are re- sponsible for half of the calcium carbonate production in the modern surface ocean, and their adorning calcite plates (coccoliths), produced intracellularly, have con- tributed to sedimentary carbonate for over 200 million years. They constitute a significant control on the partitioning of carbon between the atmosphere, ocean and sedimentary reservoirs on timescales from the instantaneous to the geological. Coc- colithophores are also uniquely placed to record aspects of the carbonate chemistry of the surface ocean, because the carbon isotopic composition of the organic matter (d13Corg) and calcite (d13Ccal) that they produce is a function of many parameters, including ambient aqueous carbon dioxide concentration [CO2]. This thesis addresses the bidirectional interaction between coccolithophores and the carbon cycle in the geological past, by asking how cellular carbon fluxes relate to physical evidence that is preserved throughout geological time. First, I present and calibrate a novel rationale for size-normalising coccolith mass, and show that over two glacial-interglacial cycles, coccolithophores appear to calcify more under high [CO2] conditions; a result that is manifest on evolutionary timescales, and is necessarily elusive to experiments. Second, I investigate the parameters controlling d13Ccal and d13Corg in coccolithophores through in vivo experimentation, and devel- opment of a model of cellular isotopic fluxes. I show that so called "vital effects" in coccolithophores arise as a result of differences in calcification to photosynthesis ratios. Third, using a combination of novel and established protocols for extraction and isotopic analysis of specific organic molecules from fossils taxonomically separated by size, I show the very first size-specific geologic time series of coccolith-associated d13Corg, and the first time-series of size-separated coccolith d13Ccal over a glacial cycle. A novel means of inferring past carbon dioxide concentrations, based on an iterative inverse modelling approach, is presented and tested.
20
Noll, Helena. "Performance trends of seasoned Two Oceans Ultramarathon runners". Master's thesis, Faculty of Health Sciences, 2020. http://hdl.handle.net/11427/32893.
Testo completoAbstract (sommario):
Background: Endurance running is known to be a prevalent sport, due to well-understood health benefits. Ultramarathon running, particularly in master athletes, has been increasingly popular. Various parameters of an individual's ability to participate in numerous such events have been explored. The performance trends of such seasoned runners have been of interest to identify trends that could influence participation and running career longevity. Aim To identify performance trends of seasoned ultramarathon runners across their Two Oceans Ultramarathon running careers. Specific Objectives The specific objectives were to 1) describe the profile of seasoned ultramarathon runners who have completed 20 or more Two Oceans Ultramarathon races, including sex, number of ultramarathons completed, medal category of peak performance and age at debut Two Oceans Ultramarathon; 2) to determine average performance, peak performance, worst performance and the pattern of improvement or decline in performance in seasoned ultramarathon runners over 20 years of race participation; 3) to determine differences in factors that may influence performance trends, such as sex, number of ultramarathons completed, medal category of peak performance and age at debut Two Oceans Ultramarathon; and 4) to determine the variation in ultramarathon performance based on the sex, number of ultramarathons completed, medal category of peak performance and age at debut Two Oceans Ultramarathon. Methods Data from 625 runners who completed 20 or more Two Oceans Ultramarathons were extracted from a publicly available website (www.twooceansmarathon.org). Finish times across their running careers were used to establish average race speeds, peak and worst performances, changes in performance over time, and coefficients of variation in performance. Groups were compared according to a) sex, b) number of Two Oceans Ultramarathons completed (20 or more than 20), c) age category of debut race, and d) medal category of peak performance. Results The finishing times and race speed results showed that males ran significantly faster than females across their 20 year Two Oceans Ultramarathon running careers (p=0.00001). Runners who completed more than 20 races had faster finishing times and race paces than those who ran 20 Two Oceans Ultramarathons (p=0.00001). When performances of the participants were analysed according to age categories, the youngest age group, namely 16-19, had the fastest average finishing times across 20 years of racing (p=0.00002). Peak and worst performances showed that best personal efforts were attained in the first quarter of the Two Oceans Ultramarathon career, and worst race performances toward the end of these running careers. It was observed that as running careers progressed over time, the groups compared showed a pattern of performance convergence as differences in finishing times and running speeds decreased. Discussion and Conclusion The findings of this study suggest that a decline in performance over time is a natural and inevitable progression of a running career. Peak performances are usually acquired within the first few years of running careers. Participation trends as well as improved performances of master runners has shown that advanced age may be favourable in successful long-term ultramarathon running. This study identified a unique cohort of athletes who have consistently maintained ultramarathon running for 20 or more years. There is an opportunity for more detailed investigation of factors contributing to the longevity of their running careers, with the goal of promoting continuity in endurance running participation and physical activity at large.
21
Gounelle, Matthieu. "Matiere extraterrestre sur terre : des oceans aux protoetoiles". Paris 7, 2000. http://www.theses.fr/2000PA077098.
Testo completoAbstract (sommario):
L'etude de la matiere extraterrestre sur terre, sous la forme des micrometeorites de taille 25 a 400 m et des meteorites de taille comprise entre le centimetre et le metre, nous a permis d'aborder deux questions scientifiques importantes : la formation des oceans terrestres et celle de notre systeme solaire. Nous presentons les collectes de micrometeorites realisees en antarctique et la controverse concernant la valeur du flux contemporain de micrometeorites sur terre. L'etude mineralogique des plus petites micrometeorites antarctiques (25-50 m) montre qu'elle sont similaires aux grosses micrometeorites antarctiques (50-400 m) et distinctes des petites micrometeorites (10-40 m) stratospheriques collectees par la nasa, suggerant que les differentes methodes de collection introduisent des biais severes. Nous avons decouvert dans des meteorites provenant d'un asteroide differencie des inclusions de taille 25 a 800 m (microclastes) que nous identifions aux micrometeorites presentes dans le systeme solaire il y a environ 4 milliards d'annees. La similarite mineralogique des microclastes avec les micrometeorites contemporaines souligne la constance de la composition du flux de micrometeorites au cours de l'histoire du systeme solaire. La demonstration de cette constance nous a permis d'ameliorer le modele propose par michel maurette d'apport sur terre par les micrometeorites de certains elements volatils et en particulier de l'eau des oceans. Nous avons egalement montre que les radionucleides eteints de courte periode presents dans les inclusions refractaires des meteorites ont ete formes par des reactions de spallation dans le systeme solaire pendant la phase protoetoile de notre soleil. Ce modele, base sur les observations des protoetoiles et sur le modele de formation d'etoiles de frank shu modifie notre perception de la formation du systeme solaire en soulignant le role de la la phase protoetoile dans la constitution des phases solides des systemes planetaires.
22
Jones, David R. "Frontiers, oceans and coastal cultures : a preliminary reconnaissance /". Access restricted: SMU users only, 2007.
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23
Wong, Anthony Ling Chiung. "Sequestering of CO2 in the oceans around Australia". Thesis, The University of Sydney, 1994. https://hdl.handle.net/2123/26895.
Testo completoAbstract (sommario):
The increasing threat of C02 to the global warming has prompted many governments to implement strategies to reduce the emission of C02 and other greenhouse gases into the atmosphere. The sequestering of C02 collected from power stations into the ocean is one of the promising strategies which can be used to achieve this goal.
The east coast of Australia is identified as a favourable location for the C02 dumping scheme. The location of power stations along the east coast, with its narrow continental shelf, has provided favourable conditions for both the economical construction and running costs, of the ocean C02 disposal scheme. Compared to other oceans in the world, the Tasman Sea, and South Pacific Ocean in general, because of its high concentration of carbonate ions in the water column and sedimentary CaCO3, provides one of the best regions in which neutralisation of C02 can take place.
The uncertainties of the fate of C02 after it has been released into the ocean and of its environmental impact are investigated. The current knowledge of C02 dumping schemes are reviewed to identify the most suitable scheme that can be adopted for Australia.
It is proposed that an injection of liquid C02 at a depth of 1,000 m would be sufficient to ensure the long-term aim of sequestering the C02 produced in Australia into the ocean as well as minimising the environmental impact to the marine environment. A special release nozzle is needed to allow maximum mixing between the liquid C02 and seawater. The creation of denser COz-enriched plume will allow the anthropogenic C02 collected to sink to greater depths. The aims of creating the sinking current are two. One is to ensure the C02 reaches a greater depth and thus increases the resident time of C02 in the ocean. The other is to allow the C02 to react with sediment CaCO3, which in general is in abundance in the Tasman Sea and the South Pacific Ocean. This neutralisation process will not only reduce the impact of C02 on the environment but also provide a permanent sequestration of C02.
24
George, Richard Llwyd Simon Frost. "Explorative coastal oceanographic visual analytics : oceans of data". Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/explorative-coastal-oceanographic-visual-analytics--oceans-of-data(4b0ef978-3337-4ff7-a2ee-af68a8eadaee).html.
Testo completoAbstract (sommario):
The widely acknowledged challenge to data analysis and understanding, resulting from the exponential increase in volumes of data generated by increasingly complex modelling and sampling systems, is a problem experienced by many researchers, including ocean scientists. The thesis explores a visualization and visual analytics solution for predictive studies of coastal shelf and estuarine modelled, hydrodynamics undertaken to understand sea level rise, as a contribution to wider climate change studies, and to underpin coastal zone planning, flood prevention and extreme event management. But these studies are complex and require numerous simulations of estuarine hydrodynamics, generating extremely large datasets of multi-field data. This type of data is acknowledged as difficult to visualize and analyse, as its numerous attributes present significant computational challenges, and ideally require a wide range of approaches to provide the necessary insight. These challenges are not easily overcome with the current visualization and analysis methodologies employed by coastal shelf hydrodynamic researchers, who use several software systems to generate graphs, each taking considerable time to operate, thus it is difficult to explore different scenarios and explore the data interactively and visually. The thesis, therefore, develops novel visualization and visual analytics techniques to help researchers overcome the limitations of existing methods (for example in understanding key tidal components); analyse data in a timely manner and explore different scenarios. There were a number of challenges to this: the size of the data, resulting in lengthy computing time, also many data values becoming plotted on one pixel (overplotting).
25
Ryan, Andrea Catherine 1968. "Should we fertilize the oceans? : examining the science, economics and policy of the iron hypothesis & ocean fertilization". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9604.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and, (S.M.)--Massachusetts Institute of Technology, Technology and Policy Program, 1998.Includes bibliographical references.
John Martin's 'iron hypothesis' (Martin, 1990), and the subsequent ground-breaking IRONEX experiments (Martin 1994, Coale 1996) have stimulated wide spread speculation about the concept of fertilizing the oceans. It has been suggested that adding nutrients to the open oceans will stimulate primary production, increasing the sequestration of carbon dioxide and enhancing potential fish harvest. Ocean fertilization has thus been heralded as a possible cure for global climate change and world food shortages. Despite considerable scientific effort, private investment, and public interest in this field there has been limited evaluation of the feasibility of ocean fertilization. This thesis attempts to fill this void by addressing not only the scientific, but also the economic and policy dimensions of ocean fertilization. It starts by reviewing current research proposals and implementation activities in the field of ocean fertilization. It identifies potential environmental impacts and biogeochemical consequences of ocean fertilization, highlighting the outstanding scientific unknowns associated with this field. The study reviews cost estimates compiled by the private sector, and examines likely practical obstacles to implementation. Legal, political and public response to fertilization proposals is also explored. Finally, some of the ethical concerns relating to fertilizing the oceans are discussed, and recommendations on future research directions and initiatives to manage this rapidly growing field are provided.
by Andrea Catherine Ryan.
S.M.
26
Kennerson, Elliott Doran. "Ocean Pictures the construction of the ocean on film /". Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/kennerson/KennersonE1208.pdf.
Testo completoAbstract (sommario):
Thesis (MFA)--Montana State University--Bozeman, 2008.Typescript. Chairperson, Graduate Committee: Ronald Tobias. Sealed Off is a DVD accompanying the thesis. Includes bibliographical references (leaves 31-35).
27
Wells, Martin Richard. "Tidal modelling of modern and ancient seas and oceans". Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497626.
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Krakauer, Nir Yitzhak Schneider Tapio. "Characterizing carbon-dioxide fluxes from oceans and terrestrial ecosystems /". Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-05262006-111949.
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Andrews, Stephen Jospeh. "Short-lived halocarbon species in the oceans and atmosphere". Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/5675/.
Testo completoAbstract (sommario):
This study aimed to improve current understanding of the emissions and distributions of very short-lived halocarbons (VSLH), thus their impact on atmospheric halogen chemistry. VSLH measurements were made during the TROMPEX campaign over the tropical Atlantic Ocean and Mauritanian upwelling region. This produced the first reported measurements of \ce{CH2ICl} by a research aircraft and identified an open-ocean source, likely linked to phytoplankton. VSLH emissions over the upwelling, implicated as a major localised source, were similar to previously measured coastal emissions which globally cover a much larger area. Thus it is likely that coastal upwelling systems in themselves are not strong global sources of VSLH. Ship-borne VSLH measurements were taken in the East Tropical Pacific (ETP) during the TORERO campaign. High sensitivity and frequency sampling gave new information regarding the distribution of VSLH, including a photolytically driven diurnal cycle of \ce{CH2I2}. Fluxes were calculated using simultaneous seawater and air measurements spanning a large area of the ETP where very few other measurements exist. Although individual VSLH depth profiles showed covariance with Chlorophyll-a (Chl-a), cross sections revealed differences in their latitudinal distributions. In fact there was little bulk correlation with surface water concentrations of Chl-a. \ce{CH2I2} and \ce{CH2ICl} displayed a negative relationship with Chl-a, attributed to physical and mixing processes. \ce{CHBr3}, \ce{CH2Br2} and \ce{CHBr2Cl} showed a relationship between surface and deep maxima concentrations suggesting that if a proxy for their production was found that this would negate the use of water column models to parameterise the surface concentrations of these species. Wind speed controls VSLH distribution in the ocean mixed layer and may even influence oceanic lifetimes of the shortest-lived species via increased turbidity and solar attenuation. It also exerts a strong control on \ce{CH3I}, \ce{CH2ICl}, \ce{CH2I2} and \ce{CHCl3} emissions and could form a link between emissions and future changes in climate.
30
Tedesco, Letizia <1978>. "Modelling coupled physical-biogeochemical processes in ice-covered oceans". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1996/1/letizia_tedesco_phd_thesis.pdf.
Testo completoAbstract (sommario):
The last decades have seen a large effort of the scientific community to study and understand the physics of sea ice. We currently have a wide - even though still not exhaustive - knowledge of the sea ice dynamics and thermodynamics and of their temporal and spatial variability. Sea ice biogeochemistry is instead largely unknown. Sea ice algae production may account for up to 25% of overall primary production in ice-covered waters of the Southern Ocean. However, the influence of physical factors, such as the location of ice formation, the role of snow cover and light
availability on sea ice primary production is poorly understood. There are only sparse localized observations and little knowledge of the functioning of sea ice biogeochemistry at larger scales.
Modelling becomes then an auxiliary tool to help qualifying and quantifying the role of sea ice biogeochemistry in the ocean dynamics. In this thesis, a novel approach is used for the modelling and coupling of sea ice biogeochemistry - and in particular its primary production - to sea ice physics. Previous attempts were based on the coupling of rather complex sea ice physical models to empirical or relatively simple biological or biogeochemical models. The focus is moved here to a more biologically-oriented point of view. A simple, however comprehensive, physical model of the sea ice thermodynamics (ESIM) was developed and coupled to a novel sea ice implementation (BFM-SI) of the Biogeochemical Flux Model (BFM). The BFM is a comprehensive model, largely used and validated in the open ocean environment and in regional seas. The physical model has been developed having in mind the biogeochemical properties of sea ice and the physical inputs required to model sea ice biogeochemistry. The central concept of the coupling is the modelling of the Biologically-Active-Layer (BAL), which is the time-varying fraction of sea ice that is continuously connected to the ocean via brines pockets and channels and it acts as rich habitat for many microorganisms. The physical model provides the key physical properties of the BAL (e.g., brines volume, temperature and salinity), and the BFM-SI simulates the physiological and ecological response of the biological community to the physical enviroment. The new biogeochemical model is also coupled to the pelagic BFM through the exchange of organic and inorganic matter at the boundaries between the two systems . This is done by computing the entrapment of matter and gases when sea ice grows and release to the ocean when sea ice melts to ensure mass conservation. The model was tested in different ice-covered regions of the world ocean to test the generality of the parameterizations. The focus was particularly on the regions of landfast ice, where primary production is generally large. The implementation of the BFM in sea ice and the coupling structure in General Circulation Models will add a new component to the latters (and in general to Earth System Models), which will be able to provide adequate estimate of the role and importance of sea ice biogeochemistry in the global carbon cycle.
31
Tedesco, Letizia <1978>. "Modelling coupled physical-biogeochemical processes in ice-covered oceans". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1996/.
Testo completoAbstract (sommario):
The last decades have seen a large effort of the scientific community to study and understand the physics of sea ice. We currently have a wide - even though still not exhaustive - knowledge of the sea ice dynamics and thermodynamics and of their temporal and spatial variability. Sea ice biogeochemistry is instead largely unknown. Sea ice algae production may account for up to 25% of overall primary production in ice-covered waters of the Southern Ocean. However, the influence of physical factors, such as the location of ice formation, the role of snow cover and light
availability on sea ice primary production is poorly understood. There are only sparse localized observations and little knowledge of the functioning of sea ice biogeochemistry at larger scales.
Modelling becomes then an auxiliary tool to help qualifying and quantifying the role of sea ice biogeochemistry in the ocean dynamics. In this thesis, a novel approach is used for the modelling and coupling of sea ice biogeochemistry - and in particular its primary production - to sea ice physics. Previous attempts were based on the coupling of rather complex sea ice physical models to empirical or relatively simple biological or biogeochemical models. The focus is moved here to a more biologically-oriented point of view. A simple, however comprehensive, physical model of the sea ice thermodynamics (ESIM) was developed and coupled to a novel sea ice implementation (BFM-SI) of the Biogeochemical Flux Model (BFM). The BFM is a comprehensive model, largely used and validated in the open ocean environment and in regional seas. The physical model has been developed having in mind the biogeochemical properties of sea ice and the physical inputs required to model sea ice biogeochemistry. The central concept of the coupling is the modelling of the Biologically-Active-Layer (BAL), which is the time-varying fraction of sea ice that is continuously connected to the ocean via brines pockets and channels and it acts as rich habitat for many microorganisms. The physical model provides the key physical properties of the BAL (e.g., brines volume, temperature and salinity), and the BFM-SI simulates the physiological and ecological response of the biological community to the physical enviroment. The new biogeochemical model is also coupled to the pelagic BFM through the exchange of organic and inorganic matter at the boundaries between the two systems . This is done by computing the entrapment of matter and gases when sea ice grows and release to the ocean when sea ice melts to ensure mass conservation. The model was tested in different ice-covered regions of the world ocean to test the generality of the parameterizations. The focus was particularly on the regions of landfast ice, where primary production is generally large. The implementation of the BFM in sea ice and the coupling structure in General Circulation Models will add a new component to the latters (and in general to Earth System Models), which will be able to provide adequate estimate of the role and importance of sea ice biogeochemistry in the global carbon cycle.
32
Naidoo, Ashley Desmond. "Ocean governance in South Africa: Policy and implementation". University of the Western Cape, 2020. http://hdl.handle.net/11394/7355.
Testo completoAbstract (sommario):
Philosophiae Doctor - PhDOcean Governance in South Africa has gained momentum over the last decade with the publication of the Green and White Papers on the National Environmental Management of the Ocean in 2012 and 2014, and the promulgation of the Marine Spatial Planning Act in 2019. Parallel to this South Africa developed and implemented the Operation Phakisa Ocean Economy Development Programme and declared a network of twenty Marine Protected Areas. The timing of this study over the last five years allowed the opportunity to undertake a detailed study of the Ocean Governance Policy Development and Implementation as the formulation of the policy and its early implementation unfolded. The Study is primarily based on interpretation of the Green and White Papers as the primary and directed ocean governance policies produced by the Government of South African and the National Department of Environmental Affairs. It places these most recent specific ocean environmental policies in the context of the many other environmental policies that exits in the country.
33
Corre, Lola. "EVOLUTION RECENTE DES OCEANS TROPICAUX: LE RÔLE DE L'INFLUENCE HUMAINE". Phd thesis, Université Paul Sabatier - Toulouse III, 2011. http://tel.archives-ouvertes.fr/tel-00690817.
Testo completoAbstract (sommario):
Au sein du système complexe que constitue le climat, l'océan joue un rôle primordial. D'une part, il enregistre et intègre les effets du changement climatique; d'autre part, les échelles de temps de ses variations naturelles, et notamment son inertie thermique environ mille fois supérieure à celle de l'atmosphère, en font un acteur important susceptible de moduler les effets futurs du changement climatique. Cette thèse se propose de mettre en évidence des signatures du changement climatique d'origine anthropique dans l'océan. Pour cela, nous étudions les évolutions observées de la température océanique de sub-surface et de la salinité océanique de surface, au cours des trente à cinquante dernières années. Des méthodes statistiques de détection de la réponse au forçage anthropique sont utilisées pour déterminer si une influence humaine peut être détectée dans les changements récents observés.
34
Johnson, Gregory Conrad. "Near-equatorial deep circulation in the Indian and Pacific Oceans /". Thesis, Woods Hole, Mass. : Woods Hole Oceanographic Institution, 1990. http://hdl.handle.net/1912/2637.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Woods Hole Oceanographic Institution and Massachusetts Institute of Technology, 1990.Funding was provided by the Office of Naval Research and a Secretary of the Navy Graduate Fellowship in Oceanography. References : p. 117-121.
35
Budin, Garry R. "An intermediate model of the tropical oceans and the atmosphere". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276560.
Testo completo
36
Kostov, Yavor (Yavor Krasimirov). "The role of high-latitude oceans in transient climate change". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104587.
Testo completoAbstract (sommario):
Thesis: Ph. D. in Climate Physics and Chemistry, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 113-119).
In this thesis we explore the role of the large-scale ocean circulation in the North Atlantic and the Southern Ocean (SO) in setting the regional and globally averaged sea surface temperature (SST) response to atmospheric forcing. We focus on the impact of anthropogenic greenhouse gases (AGHGs) and the Antarctic ozone hole and use output from general circulation models (GCMs) to estimate the corresponding climate response functions (CRFs). We show that the strength and the vertical extent of the time-mean Atlantic Meridional Overturning Circulation (AMOC) set the effective heat capacity of the World Ocean and affect the global CRF to greenhouse gas (GHG) forcing. A large fraction of the anomalous surface heat uptake induced by GHGs takes place over the North Atlantic. However, the SO also plays a significant role in removing excess heat from the atmosphere. Compared to the rest of the World Ocean, the SO warms at a much slower rate under GHG forcing. In this region the background Meridional Overturning Circulation (MOC) upwells unmodified deep water masses to the surface where they take up atmospheric heat. The modified water masses are then advected northward and subducted in the mid-latitudes. This geographical imprint of the MOC is reflected in the regional CRFs to GHGs, as seen in idealized numerical experiments with GCMs. However, GHGs are not the only major source of anthropogenic forcing on the SO. Stratospheric ozone depletion around Antarctica gives rise to an atmospheric pattern similar to the positive phase of the Southern Annular Mode (SAM): a strengthening and a southward shift of the westerlies. This poleward intensification of the winds changes the ocean circulation and gives rise to an SST response. We examine the SO CRF to a SAM pattern that arises either in the form of natural variability in unforced control experiments or as a result of imposed ozone perturbations. We analyze the SO SST response to SAM on multiple timescales and across an ensemble of GCMs from the Climate Modeling Intercomparison Project phase 5 (CMIP5). We show that the corresponding SO CRF is governed by the anomalous wind-driven MOC redistributing the background heat reservoir. The intermodel diversity in the fast and slow SST responses to SAM is partly explained by differences in the climatological thermal stratification across the ensemble of GCMs. Furthermore, we demonstrate that the sea ice response to SAM in models is very well correlated with the geographic pattern of the SST anomalies. Finally, we convolve our estimated CRFs with timeseries of historical forcing to recover the SO SST trends in numerical simulations and in observations. We contrast the multidecadal SO cooling trends against the SST warming rate in the Northern Hemisphere high latitudes. Our results imply that the recent cooling in the SO may be explained by the Antarctic ozone hole projecting on a positive SAM trend. We furthermore attempt to understand why CMIP5 models have been unable to reproduce the observed negative SST trends in the SO and instead predict regional warming. Many GCM simulations underestimate the historical SAM evolution. Another subset of CMIP5 models have biases in their climatological SO stratification, which affects their SO CRFs to SAM. The successful application of the CRF framework in the context of observed and simulated SST trends validates the results of our analysis. We are thus able to interpret the CRFs as inherent characteristics of the climate system and elucidate the importance of the high latitude oceans in transient climate change.
by Yavor Kostov.
Ph. D. in Climate Physics and Chemistry
37
Freire, Francis. "Acoustic characterization of submarine geomorphological features in the Polar Oceans". Licentiate thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-103370.
Testo completoAbstract (sommario):
Marine glacial environments contain unique seafloor features resulting from the dynamic glacial processes. Studying these submarine geomorphological features can help us understand the glacial paleo-environments so that we can predict the likely responses of present day glaciers and ice sheets to future changes in the climate. This thesis details different approaches in understanding glacial seafloor features using acoustic systems. It focuses on the novel technique of automated mapping seafloor properties using the backscatter intensity collected by acoustic multibeam echosounder systems (MBES). The aim of this thesis is to assess the potential of this unexploited data source in characterizing different glacial landforms in the polar oceans. This is done by examining the voluminous backscatter data collected by Swedish icebreaker Oden from different cruises to the polar oceans and employing an automated backscatter processing technique, the ARA algorithm, to extract surficial sediment characteristics. The results from the sediment characterization are used together with outputs from other marine acoustical systems and sediment core data to understand formational processes of the glacial submarine features. Operational issues encountered in using this technology and its viability as a tool in characterization of glacial seafloor features are discussed and suggestions are given on the improvements needed to effectively implement the method in future studies. The final part of the manuscript is a paper, published in Geo-marine Letters, where I and my co-authors show a practical application of the acoustic systems ability to characterize geomorphological features of a mass-wasting event in the deepest part of the Arctic, the Molloy Hole.
38
Roos, Lundström Frida, e Anna Mårtensson. "The Journey of Plastic trough Oceans : A study on quantifying micro plastic particles in ocean outside Costa Rican west coast". Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-28822.
Testo completoAbstract (sommario):
Since 1950, the plastic production has increased radically from 1.5 to 280 million tons in 2012. The increased production of plastic has led to oceans becoming more polluted than ever. Micro plastic particles originate from large floating plastic debris by undergoing degradation caused by UV-radiation. Due to their small size, density and colour micro plastic particles resemble marine organisms’ natural prey and are therefore ingested. This report discuss the hypotheses that there are micro plastic particles present in oceans outside of the Costa Rican west coast (hypothesis 1), that the location between the South and North Pacific gyres will result in an accumulation of plastic (hypothesis 2) and that different sampling methods will generate different types of data which makes it difficult to compare results (hypothesis 3). A manta trawl was used to collect samples in size range 1-2mm and they were quantified with a microscope. To simplifying transportation and storing, aluminum foil was used instead of glass jars to collect samples. Thereby the need of transferring material from a glass jar to a flat surface for quantifying with microscope was eliminated. One area contained 56.5 % of all gathered particles together. The result also showed that micro plastic particles are present even in protected areas.
39
Roca, Martí Montserrat. "Carbon export from the upper water column of the polar oceans by using natural radionuclides". Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/457190.
Testo completoAbstract (sommario):
Els oceans Àrtic i Austral representen el 20-35% de l’absorció oceànica global de diòxid de carboni (CO2) atmosfèric. Aquesta absorció és en part causada per la bomba biològica a través de la fixació de CO2 a la superfície de l’oceà i la transferència d’una fracció de la matèria orgànica a aigües profundes. Un dels majors reptes de la investigació polar és pronosticar els efectes del canvi climàtic sobre el funcionament de l’ecosistema marí i la captació de carboni a altes latituds. La poca informació existent sobre la dinàmica dels ecosistemes àrtic i antàrtic, la rapidesa dels efectes del canvi climàtic en els sistemes marins polars, a més de la seva rellevància en el cicle global del carboni han motivat aquesta tesi. L’objectiu d’aquest treball és contribuir al coneixement dels fluxos d’exportació de partícules i de carboni associats a la bomba biològica i dels processos que controlen aquests fluxos a la capa superficial de la columna d’aigua dels oceans polars. Els dos parells de radionúclids 234Th/238U i 210Po/210Pb s’han utilitzat en tres estudis en combinació amb altres tècniques que ofereixen informació complementària sobre paràmetres d’interès ecològic i exportació de partícules. En primer lloc, l’exportació de carboni orgànic particulat (COP) es va quantificar durant el declivi d’una floració massiva de diatomees al sector Atlàntic de l’oceà Austral a l’estiu de 2012. Els fluxos de COP mesurats a 100 m van ser elevats: 26 ± 15 mmol C m-2 d-1, de mitjana. Aquests resultats són comparables a altres estudis de floracions fitoplanctòniques en etapes tardanes a l’oceà Austral. Tot i així, l’eficiència d’exportació va ser generalment baixa: només <20% de la producció primària neta (PPN) diària va arribar als 100 m, presumiblement degut a un reciclatge actiu de carboni i nutrients a la superfície. Per contra, l’eficiència de transferència de COP mesurada entre 100 i 300 m va ser elevada (~60%), probablement com a conseqüència de l’enfonsament de diatomees. En segon lloc, els fluxos d’exportació de carboni al centre de l’Àrtic es van avaluar per primera vegada mitjançant l’aplicació conjunta dels parells 234Th/238U i 210Po/210Pb, coincidint amb el rècord mínim de gel marí del 2012. D’acord al parell 234Th/238U, els fluxos de COP a la base de la zona eufòtica van ser molt baixos (2 ± 2 mmol C m-2 d-1) durant l’agost i el setembre, quan algues de la classe de les prasinofícies haurien contribuït significativament als fluxos. Segons el parell 210Po/210Pb, els fluxos de partícules van ser majors abans del juliol/agost que a finals d’estiu, amb els màxims observats sota condicions extremes de gel associats a una exportació massiva d’agregats d’algues del gel formats per diatomees. Més del 30% de la PPN anual va ser exportada des de la zona eufòtica, indicant una elevada eficiència d’exportació de la bomba biològica al centre de l’Àrtic. Finalment, la dinàmica i l’exportació de partícules a la columna d’aigua de l’Àrtic es van estudiar mitjançant l’anàlisi de la distribució de 210Pb i 210Po a diverses plataformes continentals i conques oceàniques a l’estiu de 2007. Es van detectar dèficits de 210Po substancials (>50% respecte el 210Pb) des de la superfície als 200 m a les plataformes, però també sorprenentment a les conques. Els dèficits de 210Po van ser especialment pronunciats a la conca de Makarov, on la PPN anual va ser tres vegades superior que a la conca eurasiàtica i va estar dominada per diatomees. Aquesta observació, paral·lelament als resultats del 2012, indica que les diatomees podrien tenir un paper més important en la producció i exportació de carboni orgànic al centre de l’Àrtic del que ens pensàvem fins ara.The Arctic and Southern Oceans account together for about 20 to 35% of the global oceanic uptake of carbon dioxide (CO2) from the atmosphere. This is partly caused by the biological pump, which transforms CO2 into organic matter in surface waters and pumps a fraction of it to the deep ocean. A major challenge to polar research is to predict how climate change will affect the marine ecosystem functioning and the carbon uptake at high latitudes. The limited baseline data on ecosystem dynamics in the Arctic and Southern Oceans, the rapid impacts of climate change on polar marine systems, together with their relevance within the global carbon cycle, have motivated this thesis. This work represents an attempt to contribute to the knowledge of the particle and carbon export fluxes driven by the biological pump and the processes that control these fluxes in the upper water column of the polar oceans. The two pairs of radionuclides 234Th/238U and 210Po/210Pb have been used in three studies in combination with other techniques that provide complementary information on ecologically relevant parameters and particle export. First, the export of particulate organic carbon (POC) was quantified during the decline of a vast diatom bloom in the Atlantic sector of the Southern Ocean in summer 2012. The POC fluxes at 100 m were high, averaging 26 ± 15 mmol C m-2 d-1, which are comparable to other studies of the later stages of blooms in the Southern Ocean. However, the export efficiency of the bloom was generally low: only <20% of the daily net primary production (NPP) reached 100 m, presumably due to an active recycling of carbon and nutrients in surface waters. In contrast, the transfer efficiency of POC measured between 100 and 300 m was high (~60%), likely as a consequence of the direct sinking of diatoms. Second, carbon export fluxes in the central Arctic were assessed for the first time by the joint application of the 234Th/238U and 210Po/210Pb pairs during the record sea-ice minimum in 2012. The 234Th/238U proxy revealed that POC fluxes at the base of the euphotic zone were very low (2 ± 2 mmol C m-2 d-1) during August and September, when prasinophytes would have contributed significantly to the fluxes. On the other hand, the 210Po/210Pb proxy indicated that particle fluxes were higher before July/August than in the late summer, with maximum fluxes under heavy sea-ice conditions associated with a massive export of sea-ice algal aggregates composed of diatoms. More than 30% of the annual NPP was exported from the euphotic zone, showing a high export efficiency of the biological pump in the central Arctic. Last, particle dynamics and particle export in the water column of the Arctic Ocean were studied by analysing the distribution of 210Pb and 210Po on a pan-Arctic scale in summer 2007. Substantial deficits of 210Po (>50% with respect to 210Pb) were detected from surface waters to 200 m on the shelves, but also, and more surprisingly, in the basins. The 210Po deficits were particularly pronounced in the Makarov Basin, where the annual NPP was higher than in the Eurasian Basin by a factor of 3 and was dominated by diatoms. This observation, together with the results from 2012, indicates that diatoms could have a more important role in production and export of organic carbon in the central Arctic than is currently thought.
40
van, Opzeeland Ilse [Verfasser]. "Acoustic ecology of marine mammals in polar oceans / Ilse van Opzeeland". Bremerhaven : AWI, Alfred-Wegener-Institut für Polar- und Meeresforschung, 2010. http://d-nb.info/1010221175/34.
Testo completo
41
Gauvin, St-Denis Blaise. "Western boundary intensification of the oceans: insight from beta-plane turbulence". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18697.
Testo completoAbstract (sommario):
Western boundary intensification is a major feature of the ocean circulation. It is understood that the change in the Coriolis parameter with latitude is the principal component responsible for this phenomenon. However, traditional arguments for western boundary intensification also call for an interplay between forcing and dissipation. In this thesis, a new geometry, namely the periodic meridional channel, is compared to the closed basin setting in decaying, two-dimensional, beta-plane turbulence. By isolating the effects of the western and eastern boundaries, persistent western boundary intensification is shown to be possible as a balance between nonlinear effects and Rossby wave reflections. The conditions under which this occurs are explained, and particular attention is given to the importance of resolution in resolving the Rossby wave dynamics at the boundaries. A discussion of the regimes that do not exhibit western boundary intensification is also included.L'intensification des frontières ouest est une caractéristique majeure de la circulation océanique. Il est reconnu que la variation du paramètre de Coriolis avec la latitude est l'élément principalement responsable de ce phénomène. Néanmoins, les arguments traditionnels pour l'intensification des frontières ouest demandent aussi la présence d'une force externe et de dissipation. Dans cette thèse, une nouvelle géométrie, c'est-à-dire le canal méridional périodique, est comparée à l'environnement du bassin fermé dans la turbulence libre sur le plan beta en deux dimensions. L'isolation des effets aux frontières ouest permet l'émergence d'une intensification des frontières ouest persistante en tant qu'équilibre entre les effets non linéaires et la réflexion des ondes de Rossby. Les conditions sous lesquelles ce processus est réalisé sont expliquées, et une attention particulière est portée à l'importance de la résolution pour résoudre la dynamique des ondes de Rossby aux frontières. Une analyse des régimes qui ne manifestent pas d'intensification des frontières ouest est aussi incluse.
42
Fenton, Isabel. "Environmental controls on planktonic foraminiferal diversity in ancient and modern oceans". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/53930.
Testo completoAbstract (sommario):
Planktonic foraminifera are unicellular zooplankton, whose calcium carbonate ‘shells’, wide geographic distributions and very large population sizes combine to give them perhaps the best fossil record over the last 66 Ma of any group. Site-level assemblage diversity can be estimated comparably in the Recent and through geological time. In this thesis I model the environmental correlates of coretop (Recent) planktonic foraminiferal diversity (Chapter 2), with the aim of applying the model to the Eocene. Present-day diversity patterns are shaped by a richer combination of factors than suggested by previous work. I assess the potential of several non-biological biases to distort diversity patterns (Chapter 3). Functional and evolutionary diversity are less prone to bias than are species richness and evenness, while water depth has little impact on diversity in sites deeper than 500m. Asexuality has been suggested as an adaptation in low diversity environments. I used NanoCT scans of proloculi to test whether Neogloboquadrina pachyderma, the dominant species in polar waters, contains an asexual morph (Chapter 4), finding no support for this hypothesis. Having dealt with potential sources of bias, I use models from Chapter 2 to predict diversity in another time period, the Eocene (Chapter 5), based on current understanding of Eocene environments. The latitudinal gradient of species richness developed through the Eocene in both planktonic foraminifera and coccolithophores. Predicted and observed diversity fit well in the late – but not the early – Eocene. My analyses support two explanations for the early-Eocene mismatch. First, early Eocene climate model estimates of environment differ from the proxy records (which fit the fossil data better). Second, the intercorrelations among facets of diversity have changed through time (Chapter 6). Despite our limited understanding of some aspects of their biology, planktonic foraminifera have much to offer as a model system for macroevolution.
43
Wunderer, Christoph Frank. "Hamiltonian models of balanced vortical flow in the atmosphere and oceans". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615857.
Testo completo
44
Nicolle, Nicholas. "Managing ichthyophonus in multi-species exhibits at the two oceans aquarium". University of the Western Cape, 2020. http://hdl.handle.net/11394/7910.
Testo completoAbstract (sommario):
Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol)Ichthyophonus hoferi has been diagnosed in multiple species at the Two Oceans Aquarium, this study focuses on Rhabdosargus globiceps (White stumpnose). I. hoferi is a mesomycetozoan parasite that multiplies in blood rich organs in the fish hosts causing a wide range of clinical signs resulting in organ dysfunction. I. hoferi can be diagnosed from microscopic examination of tissue squash preparations, culture, polymerase chain reaction (PCR) and histopathology. In the literature only lethal methods of diagnosis are described. The development of a non-lethal diagnostic tool for disease monitoring is vital for collections where euthanasia of specimens is not possible.
45
Holtmeier, Matthew. "Vital Coasts, Mortal Oceans: The Pearl Button as Media Environmental Philosophy". Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/etsu-works/7825.
Testo completoAbstract (sommario):
In The Pearl Button, Patricio Guzman explores the role water played in shaping how the Selk’nam inhabited the coasts of the Tierra del Fuego in Patagonia through “cosmovisions,’ sequences that extend beyond human perception, even as they link the habitation of indigenous peoples to subsequent colonial and political projects. Guzman’s “cosmovisual aesthetic” warrants dissection in the form of a video essay because of its complicated interplay between editing and shot distance, which establishes a critical bioregionalism that acknowledges the unique qualities of place, here the Tierra del Fuego, as well as the forces of globalization that threaten it. Guzman’s cosmovisual aesthetic ranges from extreme close-ups to reveal minute details in objects to aerial shots that articulate the shapes of coasts and even to telescopic shots depicting planets and nebulae. He works with archival photography and the superimposition of images/sounds in order to create a pluriverse of peoples and environments, which moves beyond human audiovisual and temporal perception. In doing so, The Pearl Button links the ways in which the Selk’nam inhabited Chile, depending on its waters, to the ocean as the source of the colonial project of Spain and site of political murders under the later dictatorship of Augusto Pinochet. Guzman’s cinematic elaboration of Indigenous worldviews resonates with contemporary Chilean philosophers Humberto Maturana, Francisco Varela, and Ricardo Rozzi. From cybernetics to ecological philosophy, this video essay weaves the insights of these Chilean philosophers with Guzman’s cosomovisions in order to highlight the complex ecological insights at the intersection of Indigenous thought and film form. In particular, it extends Rozzi’s practical model of Field Environmental Philosophy to communicating ecological philosophy through media.
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Bots, Pieter. "Experimental investigation of calcium carbonate mineralogy in past and future oceans". Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/2393/.
Testo completoAbstract (sommario):
Inorganic marine calcium carbonate formation and mineralogy varies significantly concurrent with the solution composition. During the Phanerozoic, due to oscillations in the seawater composition, this resulted in the formation of either dominantly calcite or aragonite. Variations in seawater composition also appear to have influenced the evolution of biomineralizing organisms. Additionally, many organisms utilize amorphous calcium carbonate (ACC) during biomineralization. The occurrence of calcite and aragonite throughout the Phanerozoic and calcium carbonate biomineralization were investigated. This was done by determining the influence of solution chemistry (SO4 and Mg) on calcium carbonate formation, mineralogy and stability via a variety of laboratory and synchrotron based synthesis experiments. During the formation of aragonite and calcite, aqueous SO4 and the Mg/Ca ratio both affect the formation of calcite and aragonite. An increase in aqueous SO4 decreases the Mg/Ca ratio at which calcite is destabilized and aragonite becomes dominant. These results suggest that the models relating seawater chemistry to calcium carbonate formation needs re-evaluation. Abiotic ACC crystallization to vaterite occurs in three stages. In the first stage, ACC crystallizes to vaterite via a spherulitic growth mechanism. The second stage is characterized by surface particle growth at the expense of ACC. Finally, particle growth via Ostwald ripening is the only remaining process. This process can be described as the inorganic analogue to biological ACC crystallization, which is adjusted by organisms to produce their preferred calcium carbonate polymorph and morphology. An increase in SO4 concentration only decreases the spherulitic growth rate and Ostwald ripening, even when rapidcreekite (as an intermediate) and gypsum crystallizes. Finally, SO4 promotes the formation of vaterite. Depending on the formation process this is caused by either the stabilization of vaterite and destabilization of calcite (slow heterogeneous formation), or by the destabilization and inhibition of calcite formation (spherulitic growth).
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Laurent, Dominique. "Contribution a l'etude du comportement polarimetrique de la retrodiffusion des oceans". Nantes, 1993. http://www.theses.fr/1993NANT2053.
Testo completoAbstract (sommario):
La modelisation de la retrodiffusion des ondes electromagnetiques permet de prevoir et d'interpreter les mesures satellitaires de l'ocean; dans les radars actuels, l'etat de mer est caracterise par le coefficient de retrodiffusion. L'introduction de la polarimetrie radar en teledetection permet de traiter la totalite de l'information disponible dans l'onde retrodiffusee par la mer, en particulier l'information de phase. Un modele de calcul du comportement polarimetrique de la surface de la mer est propose; l'inversion de la signature polarimetrique de l'ocean, decrite par sa matrice de mueller moyenne, permet une estimation des caracteristiques physiques de la mer comme le vent en surface ou la constante dielectrique de l'eau de mer
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Malviya, Shruti. "Global Diatom Biodiversity : An Assessment Using Metabarcoding Approach". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112075/document.
Testo completoAbstract (sommario):
Les diatomées (Stramenopiles, Bacillariophyceae) jouent un rôle important sur le plan écologique et sont l'un des groupes phytoplanctoniques les plus divers, avec environ 1800 espèces planctoniques estimées. Bien que largement étudiées, leurs modèles de diversité et de distribution biogéographique ne sont pas bien connus. L'avènement du séquençage de l'ADN à haut débit a révolutionné les études de biodiversité moléculaire facilitant la compréhension de la biogéographie, de la structure des communautés et des processus écologiques. Les deux principaux objectifs de cette thèse sont (1) d'enquêter sur les modèles de la biodiversité mondiale et la structure des communautés de diatomées planctoniques à travers les océans du monde, et (2) de comprendre les mécanismes et processus déterminants la structure de la communauté. Cette thèse présente également une première tentative de discerner la répartition des espèces rares dans les communautés de protistes. L'étude a été réalisée en utilisant les données de metabarcoding générées à partir des échantillons biologiques et des données environnementales associées recueillies au cours de la campagne Tara Oceans (2009-2013), une circumnavigation globale couvrant toutes les principales provinces océaniques. Le matériel d’étude pour cette thèse est constitué d’un total de 12 millions de séquences de la sous unité V9 du 18S ribosomal (barcode), récoltées à partir de 46 stations soit 293 échantillons. Basée sur 63371 metabarcodes de diatomées uniques, cette étude présente une évaluation approfondie de la distribution mondiale des diatomées et de leur diversité. Les analyses révèlent des faits marquants liées à la biogéographie des diatomées, par exemple une nouvelle estimation du nombre total d'espèces de diatomées planctoniques, une diversité considérable inconnue, une diversité exceptionnellement élevée en haute mer, et des patrons de diversité complexes entre les provinces océaniques. La thèse examine ensuite les facteurs qui déterminent les modèles de bêta-diversité. Les résultats suggèrent que les diatomées sont des communautés structurées et réglementées par l'hétérogénéité de l'environnement et des processus spatiaux. Néanmoins, la majorité de la variation totale dans la composition de la communauté ne peut être expliquée ni par les facteurs environnementaux, ni par les distances spatiales, ce qui justifie les analyses futures se concentrant sur les interactions biologiques, les événements historiques, et d'autres facteurs qui ne sont pas considérés. La thèse décrit en outre une approche pour caractériser les clusters significativement associés de ribotypes concomitants. Enfin, une étude préliminaire de communautés de protistes fractionnées par taille révèle que la queue (de leurs distributions rang abondance) semble suivre un comportement en loi de puissance dans presque toutes les communautés de protistes. Cette observation peut indiquer un mécanisme universel potentiel qui peut expliquer l'organisation de communautés planctoniques marines. De façon générale, ce travail présent une perspective globale et complète de la distribution et de la diversité des diatomées dans les océans du monde. La thèse propose un cadre global pour l'évaluation de la diversité mondiale basée sur le metabarcoding, qui pourra être utilisé pour étudier la distribution et la diversité des autres lignées taxonomiques. Par conséquent, ce travail fournit un point de référence pour explorer comment les communautés microbiennes feront face à la variation des conditions environnementalesDiatoms (Stramenopiles, Bacillariophyceae) are an ecologically important and one of the most diverse phytoplanktonic groups, with an estimated ~1,800 marine planktonic species. Although widely studied, their diversity and biogeographic distribution patterns are not well known. The advent of high-throughput DNA sequencing has revolutionized molecular biodiversity studies facilitating the understanding of biogeography, community assembly and ecological processes. The two major goals of this thesis are (1) to investigate global biodiversity patterns and structure of marine planktonic diatom communities across the world’s oceans, and (2) to understand the mechanisms and processes determining their community structure and assembly. This thesis also presents an initial attempt to discern the distribution of rare species in protist communities. The study was conducted using the metabarcoding data generated from the biological samples and associated environmental data collected during the Tara Oceans (2009-2013) global circumnavigation covering all major oceanic provinces. A total of ~12 million diatom V9-18S rDNA tags from 46 sampling stations, constituting 293 size fractionated samples represent the study material for the thesis. Using 63,371 unique diatom metabarcodes, this study presents an in-depth evaluation of global diatom distribution and diversity. The analyses study draw a number of revelations related to diatom biogeography, e.g. a new estimate of the total number of planktonic diatom species, a considerable unknown diversity, exceptionally high diversity in the open ocean, complex diversity patterns across oceanic provinces. The thesis then looks into the factors determining the beta-diversity patterns. The results suggest that diatoms represent biogeographically structured ecological communities regulated by both environmental heterogeneity and spatial processes. Nonetheless, the majority of the total variation in community composition remained unexplained by either the examined measured environmental factors or spatial distances, which warrants future analyses focusing on biological interactions, historical events, and other factors that are not considered. The thesis further outlines an approach to characterize significantly associated clusters of co-occurring ribotypes. Finally, a preliminary study of size-fractionated protistan communities reveals that the tail (of their rank-abundance distributions) appears to follow a power-law behavior in almost all protistan communities. This observation may indicate a potential universal mechanism which can explain the organization of marine planktonic communities. In general, this work has presented a global comprehensive perspective on diatom distribution and diversity in the world’s oceans. The thesis offers an overall framework for metabarcoding-based global diversity assessments which in turn can be employed to study distribution and diversity of other taxonomic lineages. Consequently, this work provides a reference point to explore how microbial communities will respond/change in response to environmental conditions
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Gray, J. M. N. T. "Sea ice dynamics". Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240183.
Testo completo
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Back, Larissa. "Towards an improved understanding of deep convection patterns over the tropical oceans /". Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/10062.
Testo completo