Teses / dissertações sobre o tema "Ocean ventilation"
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MacGilchrist, Graeme. "Lagrangian perspectives on ocean ventilation". Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:de6c14b7-a55c-44e7-8c2b-2f94a601ab8e.
Texto completo da fonteMillet, Bruno. "Tracer and model constraints on the ventilation of the deep Pacific Ocean". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASJ019.
Texto completo da fonteThe Pacific Ocean represents about 50% of the global ocean volume, making it an essential player in global biogeochemical cycles and their response to external perturbations. In particular, the deep Pacific Ocean hosts major reservoirs of carbon and nutrients, whose size and variations are largely controlled by physical tracer transports. In this thesis, we aim to better understand and constrain the transport of tracers in the deep Pacific Ocean across climate states. We use historical and new observations of conservative tracers, notably oxygen isotopes, combined with numerical models of ocean circulation. We show that isopycnal mixing is an essential control of the ventilation of Pacific mid-depths. A return of abyssal waters to the surface is identified in the modern subarctic Pacific. This upwelling pathway may have been weaker during the Last Glacial Maximum about 20,000 years ago, and the deep North Pacific may have been more strongly layered; however, evidence for the required end member changes in the south of the basin to explain this deep layering remains sparse. State-of-the-art prognostic models of global ocean circulation struggle to represent observationally inferred tracer pathways and turn-over times in the modern North Pacific. However, these tracer pathways remain insufficiently constrained and the underlying dynamics are poorly understood. Analysis of in-situ measurements of the oxygen-18 (18O) isotopic ratio of seawater provides an efficient means to better constrain the origins and routes of tracers in the deep ocean: insights on these routes are derived from existing 18O observations in the Southern, Indian, and Pacific Oceans. We suggest that additional measurements of 18O from modern ocean water samples, and from calcite shells in sediment cores, would provide valuable constraints on present-day and past tracer reservoirs and fluxes in the deep ocean
Zhao, Ning Ph D. Massachusetts Institute of Technology. "Reconstructing deglacial ocean ventilation using radiocarbon : data and inverse modeling". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108960.
Texto completo da fonteCataloged from PDF version of thesis.
Includes bibliographical references (pages 137-149).
Significant changes occurred during the last deglaciation (roughly 10-20 thousand years (ka) before present) throughout the climate system. The ocean is a large reservoir of carbon and heat, however, its role during the deglaciation is still not well understood. In this thesis, I rely on radiocarbon measurements on fossil biogenic carbonates sampled from the seafloor to constrain deglacial ocean ventilation rates, using new data, an extensive data compilation, and inverse modeling. First, based on a sediment core that is absolutely dated from wooden remains, I argue that the deglacial ¹⁴C reservoir age of the upper East Equatorial Pacific was not very different from today. Combined with stable carbon isotope data, the results suggest that the deglacial atmospheric CO₂ rise was probably due to CO₂ released directly from the ocean (e.g., in the Southern Ocean) to the atmosphere rather than first mixed through the upper ocean. Then using a high-deposition-rate sediment core located close to deep water formation regions in the western North Atlantic, I show that compared to today, the mid-depth water production in the North Atlantic was probably stronger during the Younger Dryas cold episode, and weaker during other intervals of the late deglaciation. However, the change was not as large as suggested by previous studies. Finally, I compile published and unpublished deep ocean ¹⁴C data, and find that the ¹⁴C activity of the deep ocean mirrors that of the atmosphere during the past 25 ka. A box model of modern ocean circulation is fit to the compiled data using an inverse method. I find that the residuals of the fit can generally be explained by the data uncertainties, implying that the compiled data jointly do not provide strong evidence for basin-scale ventilation changes. Overall, this thesis suggests that, although deep ocean ventilation may have varied at some locations during the last deglaciation, the occurrence of basin-scale ventilation changes are much more difficult to be put on a firm footing. An imbalance between cosmogenic production and radioactive decay appears as the most natural explanation for the deglacial ¹⁴C activity decline observed in both the atmosphere and the deep ocean.
by Ning Zhao.
Ph. D.
Stöven, Tim [Verfasser]. "Ocean ventilation and anthropogenic carbon based on evaluated transient tracer applications / Tim Stöven". Kiel : Universitätsbibliothek Kiel, 2015. http://d-nb.info/107440470X/34.
Texto completo da fonteChandana, K. R., Ravi Bhushan e A. J. T. Jull. "Evidence of Poor Bottom Water Ventilation during LGM in the Equatorial Indian Ocean". FRONTIERS MEDIA SA, 2017. http://hdl.handle.net/10150/626606.
Texto completo da fonteRadwan, Jean. "Contribution à la mise au point d'une technique de mesure du Kr85 dans l'océan : étude et réalisation d'un système d'extraction, de séparation et de mesure du Krypton total dissous". Paris 6, 1986. http://www.theses.fr/1986PA066529.
Texto completo da fonteNeale, James Richard Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Experimental and numerical investigation of noise generation from the expansion of high velocity HVAC flows on board ocean going fast ferries". Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2006. http://handle.unsw.edu.au/1959.4/28371.
Texto completo da fonteVergara, Oscar. "Ventilation de la circulation océanique dans le Pacifique sud-est par les ondes de Rossby et l'activité méso-échelle : téléconnexions d'ENSO". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30356/document.
Texto completo da fonteThe oceanic circulation in the subthermocline of the South Eastern Pacific remains poorly documented although this region is thought to play a key role in the climate variability owed to, in particular, the presence of an extended oxygen minimum zone (OMZ) that intervenes in the carbon and nitrogen cycle. The subthermocline in this region is also largely unmonitored and historical estimates of ocean heat content are mostly limited to the upper 500 m. In this thesis we document various oceanic processes at work in the subthermocline based on a regional modeling approach that is designed to take in account the efficient oceanic teleconnection from the equatorial region to the mid-latitudes, in particular at ENSO (El Niño Southern Oscillation) timescales. The focus is on two aspects: (1) the seasonality of the turbulent flow and its role in modulating the OMZ volume off Peru, and (2) the planetary wave fluxes associated with interannual to decadal timescales. It is first shown that the vertical energy flux at interannual timescales can be interpreted as resulting from the vertical propagation of extra-tropical Rossby waves remotely forced from the equatorial region. This flux primarily results from extreme Eastern Pacific El Niño events, despite that a significant fraction of interannual Sea Surface Temperature (SST) variability in the tropical Pacific is also associated with Central Pacific El Niño events and La Niña events. Vertically propagating energy flux at decadal timescales is also evidenced in the model, which, like for the interannual flux, is marginally impacted by mesoscale activity. On the other hand, the wave energy beams experience a marked dissipation in the deep-ocean ( 2000 m) which is interpreted as resulting from vertical diffusivity. While the oxygen field within the OMZ appears to be influenced by the vertical propagation of isopycnals height anomalies, induced by the seasonal Rossby waves, the seasonality of the OMZ is shown to be dominantly associated with the seasonal change in the eddy flux at its boundaries. Implications of the results for the study of both the low-frequency variability of the OMZ and the Earth's energy budget are discussed
Akhoudas, Camille. "Un nouveau regard sur la dynamique de l’océan Austral et ses interactions avec la cryosphère révélé par une approche isotopique". Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS464.
Texto completo da fonteThe Southern Ocean is a key component in global ocean circulation and the Earth's climate system. Despite the increase of in situ observations in this remote region since the 1990s (notably with the « satellite era » and major international observation programs such as WOCE, CLIVAR, GO-SHIP, or ARGO), this immense ocean remains largely unknown. However, it is essential to observe and understand the mechanisms of its dynamics as well as its variability with the aim to predict the future evolution of the climate system. In particular, one important characteristic of the Southern Ocean is that it is one of the main sites of deep ocean ventilation, which allows redistribution and sequestration of heat, freshwater, carbon, oxygen, and nutrients. This ventilation process is mainly associated with a vertical circulation connecting the ocean surface to the abyss, fueled by intense interactions and exchanges of energy and buoyancy fluxes between atmosphere, ocean and cryosphere. In this thesis, I apprehend some aspects of the Southern Ocean dynamics by providing a mechanistic view of large-scale circulation and its ongoing changes. The approach I use throughout this thesis is based on observations of stable water isotopes, a passive tracer commonly used in a large number of earth science disciplines, but until recently only sparsely used in physical oceanography. Stable water isotopes constitute a robust tool which, as a tracer of the origin of water, help to better characterize the different components of the hydrological cycle as well as its evolution. In particular, the isotopic composition of seawater represents an important imprint of water masses, containing information on the conditions of their formation and their evolution. In this thesis, beyond the important methodological work at sea and in the laboratory for the sampling, analysis and calibration of isotopic measurements, I use the stable water isotopes in combination with other more conventional tracers to apprehend, with a new perspective, the questions of the role of interactions between the Southern Ocean and the Antarctic Ice Sheet in large-scale circulation, the signature of surface waters in the abyss, or even the impact of changes in atmospheric or cryosphere regimes on the surface ocean. Beyond the only use of stable water isotopes, original approaches have allowed me to document melting and refreezing of one of the largest ice shelves in the world, which influences the characteristics of the dense waters, precursors of abyssal waters produced in the Weddell Sea. My results also reveal the proportion of these dense waters in bottom water formation in the Atlantic sector of the Southern Ocean. We detail the processes that lead to the formation of bottom waters and with this new insight, we demonstrate that past estimates of bottom water production, in apparent contradiction, were actually focusing on different processes. Finally, I propose to quantify the changes in freshwater inputs over the past three decades that influence the trends in surface properties in the Indian sector of the Southern Ocean. The results demonstrate that changes in the precipitation regime explain changes in the surface ocean characteristics impacting stratification with consequences for large-scale water mass formation and overturning circulation in the Southern Ocean
Andrié, Chantal. "Utilisation des traceurs helium-3 et tritium en oceanographie". Paris 6, 1987. http://www.theses.fr/1987PA066241.
Texto completo da fonteCartapanis, Olivier. "Variabilité de la zone de minimum d’oxygène du Pacifique Est équatorial au cours du Quaternaire récent". Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4365/document.
Texto completo da fonteThis thesis aims at documenting the spatiotemporal variations of the Oxygen Minimum Zone (OMZ) of the northeastern Pacific, and identifying the mechanisms that caused theses variations. The study is based on the geochemical analyses of major, minor, and trace elements of sediments from the northeastern Pacific, by combining ICP-MS and XRF scans measurements. These measurements allowed distinguishing the effect of biologic productivity and oceanic ventilation on sediment oxygenation. I was able to highlight the predominant impact of the productivity off the Baja California Margin (23°N), which varied in phase with the high northern Atlantic temperature across the past 120,000 years. Moreover, oceanic ventilation did play an important role off the Papagayo Gulf (12°N), because of the advection of water mass coming from the high northern and southern latitudes. OMS intensity in the northeastern Pacific could thus be influenced by changes in the atmospheric and oceanic circulation, in relation to high northern and southern latitudes climates
Paillet, Jérôme. "Eau modale et ventilation océanique en Atlantique nord-est". Brest, 1996. http://www.theses.fr/1996BRES2004.
Texto completo da fonteGrant, Hazel Christine. "The role of Weddell Sea deep and bottom waters in ventilating the deep ocean". Thesis, University of East Anglia, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492970.
Texto completo da fonteSchwarzkopf, Franziska Ulrike [Verfasser]. "Ventilation pathways in the tropical Atlantic and Pacific Oceans with a focus on the Oxygen Minimum Zones : development and application of a nested high-resolution global model system / Franziska Ulrike Schwarzkopf". Kiel : Universitätsbibliothek Kiel, 2016. http://d-nb.info/1104733676/34.
Texto completo da fonteMin, Dong-Ha. "Studies of large-scale intermediate and deep water circulation and ventilation in the North Atlantic, South Indian and Northeast Pacific Oceans, and in the East Sea (Sea of Japan), using chlorofluorocarbons as tracers /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035926.
Texto completo da fontePrasanna, K. "CO2 Ventilation, Hydrological Cycle over Southern Ocean and Clumped Isotope Thermometry in Biogenic Carbonates". Thesis, 2016. http://etd.iisc.ac.in/handle/2005/3142.
Texto completo da fontePrasanna, K. "CO2 Ventilation, Hydrological Cycle over Southern Ocean and Clumped Isotope Thermometry in Biogenic Carbonates". Thesis, 2016. http://hdl.handle.net/2005/3142.
Texto completo da fonte