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Dissertations / Theses on the topic 'Ocean data'

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Published: 6 September 2023

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1

Woodgate, Rebecca A. "Data assimilation in ocean models." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359566.

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2

Moore, A. M. "Data assimilation in ocean models." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375276.

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3

Anderson, Timothy A. "Visualization and assessment of Global Ocean Data assimulation experiment profile data for the Pacific Ocean." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA395809.

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4

Lguensat, Redouane. "Learning from ocean remote sensing data." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2017. http://www.theses.fr/2017IMTA0050/document.

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Reconstruire des champs géophysiques à partir d'observations bruitées et partielles est un problème classique bien étudié dans la littérature. L'assimilation de données est une méthode populaire pour aborder ce problème, et se fait par l'utilisation de techniques classiques, comme le filtrage de Kalman d’ensemble ou des filtres particulaires qui procèdent à une évaluation online du modèle physique afin de fournir une prévision de l'état. La performance de l'assimilation de données dépend alors fortement de du modèle physique. En revanche, la quantité de données d'observation et de simulation a augmenté rapidement au cours des dernières années. Cette thèse traite l'assimilation de données d'une manière data-driven et ce, sans avoir accès aux équations explicites du modèle. Nous avons développé et évalué l'assimilation des données par analogues (AnDA), qui combine la méthode des analogues et des méthodes de filtrage stochastiques (filtres Kalman, filtres à particules, chaînes de Markov cachées). Des applications aux modèles chaotiques simplifiés et à des études de cas de télédétection réelle (température de surface de lamer, anomalies du niveau de la mer), nous démontrons la pertinence d'AnDA pour l'interpolation de données manquantes des systèmes dynamiques non linéaires et à haute dimension à partir d'observations irrégulières et bruyantes.Motivé par l'essor du machine learning récemment, la dernière partie de cette thèse est consacrée à l'élaboration de modèles deep learning pour la détection et de tourbillons océaniques à partir de données de sources multiples et/ou multi temporelles (ex: SST-SSH), l'objectif général étant de surpasser les approches dites expertes
Reconstructing geophysical fields from noisy and partial remote sensing observations is a classical problem well studied in the literature. Data assimilation is one class of popular methods to address this issue, and is done through the use of classical stochastic filtering techniques, such as ensemble Kalman or particle filters and smoothers. They proceed by an online evaluation of the physical modelin order to provide a forecast for the state. Therefore, the performanceof data assimilation heavily relies on the definition of the physical model. In contrast, the amount of observation and simulation data has grown very quickly in the last decades. This thesis focuses on performing data assimilation in a data-driven way and this without having access to explicit model equations. The main contribution of this thesis lies in developing and evaluating the Analog Data Assimilation(AnDA), which combines analog methods (nearest neighbors search) and stochastic filtering methods (Kalman filters, particle filters, Hidden Markov Models). Through applications to both simplified chaotic models and real ocean remote sensing case-studies (sea surface temperature, along-track sea level anomalies), we demonstrate the relevance of AnDA for missing data interpolation of nonlinear and high dimensional dynamical systems from irregularly-sampled and noisy observations. Driven by the rise of machine learning in the recent years, the last part of this thesis is dedicated to the development of deep learning models for the detection and tracking of ocean eddies from multi-source and/or multi-temporal data (e.g., SST-SSH), the general objective being to outperform expert-based approaches
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5

Zika, Jan David Climate &amp Environmental Dynamics Laboratory Faculty of Science UNSW. "Quantifying ocean mixing from hydrographic data." Awarded by:University of New South Wales. Climate & Environmental Dynamics Laboratory, 2010. http://handle.unsw.edu.au/1959.4/44872.

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The relationship between the general circulation of the ocean and, along-isopycnal and vertical mixing is explored. Firstly, advection down isopycnal tracer gradients is related to mixing in specific regions of the ocean. Secondly, a general inverse method is developed for estimating both mixing and the general circulation. Two examples of down gradient advection are explored. Firstly the region of Mediterranean outflow in the North Atlantic. Given a known transport of warm salty water out of the Mediterranean Sea and the mean hydrography of the eastern North Atlantic, the vertical structure of the along-isopycnal mixing coefficient, K, and the vertical mixing coefficient, D, is revealed. Secondly, the Southern Ocean Meridional Overturning Circulation, SMOC, is investigated. There, relatively warm salty water is advected southward, along-isopycnals, toward fresher cooler surface waters. The strength and structure of the SMOC is related to K and D by considering advection down along-isopycnal gradients of temperature and potential vorticity. The ratio of K to D and their magnitudes are identified. A general tool is developed for estimating the ocean circulation and mixing; the \textit{tracer-contour inverse method}. Integrating along contours of constant tracer on isopycnals, differences in a geostrophic streamfunction are related to advection and hence to mixing. This streamfunction is related in the vertical, via an analogous form of the depth integrated thermal wind equation. The tracer-contour inverse method combines aspects of the box, beta spiral and Bernoulli methods. The tracer-contour inverse method is validated against the output of a layered model and against in-situ observations from the eastern North Atlantic. The method accurately reproduces the observed mixing rates and reveals their vertical structure.
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6

Lawrence, David Hawkesford. "Ocean colour analysis using CZCS data." Thesis, University of Plymouth, 1987. http://hdl.handle.net/10026.1/1731.

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7

Melo, Jose Luis Branco Seabra de. "Nonlinear parametric wave model compared with field data." Monterey, Calif. : Naval Postgraduate School, 1985. http://catalog.hathitrust.org/api/volumes/oclc/57738811.html.

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8

Liu, Liyan Jones C. K. R. T. "Lagrangian data assimilation into layered ocean model." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,786.

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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.
Title from electronic title page (viewed Dec. 18, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Mathematics." Discipline: Mathematics; Department/School: Mathematics.
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9

Phillipson, Luke. "Ocean data assimilation in the Angola Basin." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/62645.

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The predictability of the ocean currents and the Congo River plume within the Angola Basin was investigated using the Regional Ocean Modelling System (ROMS) with data assimilation (4D-Var). Firstly, the impact of assimilating a novel remote-sensing data set, satellite-derived ocean currents (OSCAR) as compared to the more conventional satellite sea surface height (SSH) on ocean current predictability was assessed. In comparing 17 simulated and observed drifters throughout January-March 2013 using four different metrics, it was found that OSCAR assimilation only improves the Lagrangian predictability of ocean currents as much as altimetry assimilation. The impact of combining the aforementioned remote-sensing observations (OSCAR or SSH) with drifters was then investigated throughout the same period to assess whether this combination could improve upon assimilating the drifters alone on ocean current predictability. It was found that the addition of drifters significantly improves the Lagrangian predictability of the ocean currents in comparison to either altimetry or OSCAR as expected. More surprisingly, the assimilation of either SSH or OSCAR with the drifter velocities does not significantly improve the Lagrangian predictability compared to the drifter assimilation alone, even degrading predictability in some cases. Additionally, a new metric denoted the crossover time was formulated using the drifters, defined as the time it takes for a numerical model to equal the performance of persistence. In addition to ROMS, a global ocean model was also evaluated to demonstrate and quantify the metric fully. Finally, the impact of assimilating a recently available advanced version of a satellite salinity product (SMOS), on the Congo River plume was investigated. With some metrics specifically focusing on validating the Congo River plume, it was found that the assimilation of SMOS improved the representation of the plume within the model as well as the modelled salinity fields.
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10

Navarro, Moisés M. "Ocean wave data analysis using Hilbert transform techniques." Thesis, Monterey, California. Naval Postgraduate School, 1996. http://hdl.handle.net/10945/32022.

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A novel technique to determine the phase velocity of long-wavelength shoaling waves is investigated. Operationally, the technique consists of three steps. First, using the Hilbert transform of a time series, the phase of the analytic signal is determined. Second, the correlations of the phases of analytic signals between two points in space are calculated and an average time of travel of the wave fronts is obtained. Third, if directional spectra are available or can be determined from time series of large array of buoys, the angular information can be used to determine the true time of travel. The phase velocity is obtained by dividing the distance between buoys by the correlation time. Using the Hilbert transform approach, there is no explicit assumption of the relation between frequency and wavenumber of waves in the wave field, indicating that it may be applicable to arbitrary wave fields, both linear and nonlinear. Limitations of the approach are discussed.
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11

Onabid, Mathias Akong. "Improved ocean chlorophyll estimates from remote sensed data." Thesis, University of Glasgow, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438091.

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12

Reiter, Edmund. "Imaging of large offset ocean bottom seismic data." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/54967.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.
Includes bibliographical references (leaves 139-146).
by Edmund C. Reiter.
Ph.D.
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13

Mirhi, Mohamad H. (Mohamad Hussein). "Design of interactive maps for ocean dynamics data." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121860.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references.
Comprehensive spatiotemporal modeling and forecasting systems for ocean dynamics necessitate robust and efficient data delivery and visualization techniques. The multi-disciplinary simulation, estimation, and assimilation systems group at MIT (MSEAS) focuses on capturing and predicting diverse ocean dynamics, including physics, acoustics, and biology on varied scales, thereby developing new methods for multi-resolution ocean prediction and analysis, including data generation and assimilation. The group has primarily used non-interactive ocean plots to visualize its simulated and measured data. Although these maps and sections allow for analysis of ocean physics and the underlying numerical schemes, more interactive maps provide more user control over depicted data, allowing easier study and pattern identification on multiple scales. Integrating static and geospatial data in dynamic visualization creates a heightened viewpoint for analysis, enhances ocean monitoring and prediction, and contributes to building scientific knowledge. This thesis focuses on explaining the motivation behind and the methodologies applied in designing these interactive maps.
by Mohamad Mirhi.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Mechanical Engineering
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14

Augusto, Fabio Lekecinskas. "An improvement on the gas transfer velocity model with application to scatterometer data." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/21/21135/tde-07102015-143819/.

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The increase of carbon dioxide in the atmosphere observed in recent decades is causing the acidification of the oceans besides the global warming. The amount of carbon dioxide that crosses the air-sea interface is not well known because this amount depends upon the partial pressure of carbon dioxide and the gas transfer velocity. The gas transfer velocity is a variable based on Fick\'s Law of Diffusion and is normally parametrized as a function of wind velocity at the height of 10 meters. However, the result of this parametrization have errors greater than 100%. Newer parametrization include the effects of temperature, friction velocity and the presence of surface waves. Based on the simplest model of air-sea gas transfer model, the stagnant film theory, this study developed a methodology to improve the knowledge of the relation between the gas transfer velocity and the mean square slope. This variable accounts for the mean curvature of the waves in the surface. The data used was gathered within the scope of the DOGEE project in 2007. In that, a drifting buoy measured several parameters relative to the waves and the gas transfer velocity. The results show that the mean square slope calculated with waves whose wavenumber is between 40 and 50 radians per meter has the lowest root mean square errors of the regression between the mean square slope and the gas transfer velocity. This result showed to be very consistent when applied to the QuikSCAT scatterometer data and compared to a recent published study.
O aumento da concentração de dióxido de carbono na atmosfera observado nas últimas décadas é responsável por alterações climáticas e ambientais em escala global. Uma das consequências desse aumento da concentração de gás carbônico é o aquecimento global. Outra consequência é a acidificação dos oceanos. Isto ocorre devido ao dióxido de carbono atravessar a interface ar-mar e se dissolver no oceano. A quantidade de dióxido de carbono que atravessa a interface ar-mar é um dado não conhecido com precisão devido a esta quantidade depender de uma constante conhecida por velocidade de transferência do gás carbônico. Esta velocidade de transferência é normalmente uma parametrização do transporte turbulento do gás na interface oceano-atmosfera. Como o dado mais comum para essa parametrização é o vento à altura de 10 metros, muitos estudos foram desenvolvidos utilizando esta variável. No entanto, os resultados destas parametrizações possuem erros da ordem de 100%. Este estudo desenvolveu uma metodologia para obter uma melhor estimativa da velocidade de transferência. Para isto, optou-se por relacionar esta variável à inclinação quadrática média (MSS) das ondas. Segundo a literatura científica recente, o MSS é uma variável mais relacionada à transferência gasosa do que o vento a 10 metros de altura. Os resultados mostram que a inclinação quadrática média calculado com números de onda entre 40 e 50 radianos por metro possuem o menor erro no ajuste linear com os dados de velocidade de transferência. Este resultado indica uma mudança da dinâmica da interface nesse intervalo de número de onda. Com isso, um novo ajuste linear entre o MSS e a velocidade de transferência é sugerido como parametrização. A aplicação desta nova parametrização a dados de satélite do tipo escaterômetro mostrou-se consistente quando comparado a um estudo recente relacionando a velocidade de transferência do gás carbônico diretamente a dados do satélite oceanográfico QuikSCAT.
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15

Rana, Haris Sarwar. "Indian Ocean surface circulations and their connection to Indian Ocean dipole, identified from Ocean Surface Currents Analysis Real Time (OSCAR) data." Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://handle.dtic.mil/100.2/ADA483452.

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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2008.
Thesis Advisor(s): Chu, Peter C. "June 2008." Description based on title screen as viewed on August 26, 2008. Includes bibliographical references (p. 67-71). Also available in print.
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16

Weaver, Anthony T. "Variational data assimilation in numerical models of the ocean." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240442.

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17

Martin, Matthew J. "Data assimilation in ocean circulation models with systematic errors." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365425.

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18

Hilton, Richard Daniel. "Non-ocean applications of multi-mission satellite altimeter data." Thesis, De Montfort University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422592.

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19

Kehoe, Kenneth. "Ocean sun glint albedo estimation from geostationary satellite data." Thesis, The University of Arizona, 2002. http://hdl.handle.net/10150/278794.

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Specular reflection off the ocean surface has been used to derive ocean wave heights and surface wind speeds, but the effect that waves have on ocean surface reflection of incident solar radiation is not fully understood. This study focussed on measuring how sun glint affects the Earth's radiation budget, by including the previously ignored specularly reflecting region. Measurements collected by the GOES-10 geostationary satellite were used to produce an effective sun glint albedo to characterize the accuracy of omitting the glint region from the radiation budget. Estimations were made using the Cox/Munk statistical distribution model. These results varied slightly as a function of wind speed where a 6 m/s surface wind speed produced an effective clear sky sun glint albedo of 1.9%. This value was less than the satellite measured value of 2.2 ± 0.1% for measurements in the cloud free region. Estimates including clouds show a smaller glitter effect of 1.7 ± 0.1%. These values were then extrapolated to the full Earth value by including ocean fraction resulting in global values of 1.6 ± 0.1% and 1.2 ± 0.1% for clear sky and cloudy respectively.
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20

Herman, James Stackpole. "A sail force dynamometer : design, implementation and data handling." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14491.

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21

Wist, Hanne Therese. "Statistical properties of successive ocean wave parameters." Doctoral thesis, Norwegian University of Science and Technology, Norwegian University of Science and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16.

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For random waves the free surface elevation can be described by a number of individual wave parameters. The main objective of this work has been to study the statistical properties of individual parameters in successive waves; the wave crest height, the wave height and the wave period.

In severe sea states the wave crest heights exhibit a nonlinear behavior, which must be reflected in the models. An existing marginal distribution that uses second order Stokes-type nonlinearity is transformed to a two-dimensional distribution by use of the two–dimensional Rayleigh distribution. This model only includes sum frequency effects. A two-dimensional distribution is also established by transforming a second order model including both sum and different frequency effects. Both models are based on the narrow-band assumption, and the effect of finite water depth is included. A parametric wave crest height distribution proposed by Forristall (2000) has been extended to two dimensions by transformation of the two-dimensional Weibull distribution.

Two successive wave heights are modeled by a Gaussian copula, which is referred to as the Nataf model. Results with two initial distributions for the transformation are presented, the Næss (1985) model and a two-parameter Weibull distribution, where the latter is in best agreement with data. The results are compared with existing models. The Nataf model has also been used for modeling three successive wave heights. Results show that the Nataf transformation of three successive wave heights can be approximated by a first order autoregression model. This means that the distribution of the wave height given the previous wave height is independent of the wave heights prior to the previous wave height. The simulation of successive wave heights can be done directly without simulating the time series of the complete surface elevation.

Successive wave periods are modeled with the Nataf transformation by using a two-parameter Weibull distribution and a generalized Gamma distribution as the initial distribution, where the latter is in best agreement with data. Results for the marginal and two-dimensional distributions are compared with existing models. In practical applications, it is often of interest to consider successive wave periods with corresponding wave heights exceeding a certain threshold. Results show that the distribution for successive wave periods when the corresponding wave heights exceed the root-mean-square value of the wave heights can be approximated by a multivariate Gaussian distribution. When comparing the results with data, a long time series is needed in order to obtain enough data cases. Results for three successive wave periods are also presented.

The models are compared with field data from the Draupner field and the Japan Sea, and with laboratory data from experiments at HR Wallingford. In addition, data from numerical simulations based on second order wave theory, including both sum and frequency effects, are included.

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22

Li, Dan 1969. "Low-frequency bottom backscattering data analysis using multiple constraints beamforming." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36060.

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23

Lu, Jingxi. "Adjoint data assimilation in an equatorial coupled atmosphere-ocean model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25100.pdf.

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24

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.

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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.
Cataloged 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.
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25

Pinkerton, Matthew H. "Validating remotely-sensed ocean colour data using a moored databuoy." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/42165/.

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SeaWiFS, and the other new generation of ocean colour sensors, must be backed by comprehensive calibration and validation programmes if they are to achieve their aims of accurate, synoptic, global measurement of oceanic phytoplankton biomass and production. In situ measurements of normalised water-leaving radiance {L^) made simultaneously with satellite measurements can complement on-orbit methods of tracking changes in the calibration of the satellite radiometer and allow end-to-end vicarious validation of the whole remote sensing method, including new atmospheric correction methods. A moored, optical databuoy was developed to measure L^ in the western English Channel for extended periods. Tests indicate that the buoy is capable of measuring spectral incident irradiance with less than 10% error and water-leaving radiance with less than 20% error; the errors are reduced by averaging the data. There were 24 match-ups with good quality SeaWiFS data at the buoy site during the 10 months of deployment between May 1997 and September 1998. The RMS differences between the buoy and SeaWiFS measurements ofLw varied from 49.5% at 555 nm to 101.5% at 412 nm. This leads to the diffuse attenuation at 490 nm [^490)] being systematically overestimated by the SeaWiFS algorithm by between 50 and 70%, with an RMS difference of 68.6%. Near surface chlorophyll-a concentrations (Ca) differ from those based on the buoy optical measurements by between -52% (SeaWiFS estimate lower than buoy estimate) to +123%, with an RMS difference of 57%. The RMS differences in measurements of Lwn could be reduced to less than 13% by increasing the calibration coefficients of SeaWiFS by between 3.7% and 0.25% in the visible bands and by tuning the extrapolation of aerosol radiances from the near infra red to the visible wavelengths. This study also found that remotely sensed measurements of A^490)an^ Ca may be biased because of undersampling.
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McLean, Lorna M. "The determination of ocean correlation scales using argo float data." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/191939/.

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The scales over which ocean properties vary play a critical role in the assimilation of ocean data. Previous studies do not explore these scales in great detail and pre-Argo observations limited investigations to the upper ocean (<500m). In this study Argo data have been used to develop a method of estimating the correlation scales of salinity on depth and potential temperature surfaces to depths of 1600m. Zonal and meridional scales of mean field salinity and salinity anomalies are examined in the Pacific and Atlantic. Correlation scales are calculated by the fitting of a Gaussian function to the differences in salinity between observation pairs that satisfy given spatial and temporal separation requirements. The intercept and scale that result in the best fit are taken to be the optimum values for the region. The significance of the correlation scale is tested by the calculation of the F-ratio. Comparisons of the scales show mean field scales to be larger than anomaly field scales. Scales are found to be anisotropic in all cases but anomaly field scales differ in size and pattern between the Pacific and Atlantic. Correlation scales exhibit dependence on latitude and depth with longer scales observed in the tropics and in general, scales shorten with depth down to ?800m and then increase below this. Comparing scales of S(z ) with those of S(?) indicates there is no significant difference between z and ? scales in the Pacific. However, salinity differences on ?-surfaces are lower than on z, linked to the heaving of water masses and the vertical gradient of salinity. Atlantic scales of S(?)prove to be significantly larger than those of S(z ). Recommendations are made for the use of these correlation scales in assimilation models
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27

Ross, Ian. "Nonlinear dimensionality reduction methods in climate data analysis." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492479.

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Linear dimensionality reduction techniques, notably principal component analysis, are widely used in climate data analysis as a means to aid in the interpretation of datasets of high dimensionality. These hnear methods may not be appropriate for the analysis of data arising from nonlinear processes occurring in the climate system. Numerous techniques for nonlinear dimensionality reduction have been developed recently that may provide a potentially useful tool for the identification of low-dimensional manifolds in climate data sets arising from nonlinear dynamics. In this thesis I apply three such techniques to the study of El Niño/Southern Oscillation variability in tropical Pacific sea surface temperatures and thermocline depth, comparing observational data with simulations from coupled atmosphere-ocean general circulation models from the CMIP3 multi-model ensemble.
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28

Dail, Holly Janine. "Atlantic Ocean circulation at the last glacial maximum : inferences from data and models." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78367.

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Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 221-236).
This thesis focuses on ocean circulation and atmospheric forcing in the Atlantic Ocean at the Last Glacial Maximum (LGM, 18-21 thousand years before present). Relative to the pre-industrial climate, LGM atmospheric CO₂ concentrations were about 90 ppm lower, ice sheets were much more extensive, and many regions experienced significantly colder temperatures. In this thesis a novel approach to dynamical reconstruction is applied to make estimates of LGM Atlantic Ocean state that are consistent with these proxy records and with known ocean dynamics. Ocean dynamics are described with the MIT General Circulation Model in an Atlantic configuration extending from 35°S to 75°N at 1° resolution. Six LGM proxy types are used to constrain the model: four compilations of near sea surface temperatures from the MARGO project, as well as benthic isotope records of [delta]¹⁸O and [delta]¹³C compiled by Marchal and Curry; 629 individual proxy records are used. To improve the fit of the model to the data, a least-squares fit is computed using an algorithm based on the model adjoint (the Lagrange multiplier methodology). The adjoint is used to compute improvements to uncertain initial and boundary conditions (the control variables). As compared to previous model-data syntheses of LGM ocean state, this thesis uses a significantly more realistic model of oceanic physics, and is the first to incorporate such a large number and diversity of proxy records. A major finding is that it is possible to find an ocean state that is consistent with all six LGM proxy compilations and with known ocean dynamics, given reasonable uncertainty estimates. Only relatively modest shifts from modern atmospheric forcing are required to fit the LGM data. The estimates presented herein succesfully reproduce regional shifts in conditions at the LGM that have been inferred from proxy records, but which have not been captured in the best available LGM coupled model simulations. In addition, LGM benthic [delta]¹⁸O and [delta]¹³C records are shown to be consistent with a shallow but robust Atlantic meridional overturning cell, although other circulations cannot be excluded.
by Holly Janine Dail.
Ph.D.
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29

Tyler, Robert H. "Electromagnetic fields generated by ocean currents and the potential for using geomagnetic data in ocean and climate studies." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39884.

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The ocean currents flowing through the earth's main magnetic field are known to induce secondary magnetic fields. Hence, variations in the ocean circulation induce variations in the net magnetic field. This research is aimed at exploring the potential for using geomagnetic data to study variability in ocean circulation and climate.
First, general relativity theory is used to formally establish the proper set of electromagnetic equations to be used for observers in a rotating (accelerating) frame of reference observing a medium (the ocean, in this case) with relative velocity. Extra terms due to rotation are derived and described and a generalized Schiff's charge density is shown to be potentially significant for the application to ocean circulation.
We extend the theory of electromagnetic fields generated by ocean currents. Many analytical solutions are found for idealized ocean features including sheared flow, jets, and a Stommel gyre. Results indicate that the ocean-induced magnetic fields will typically have magnitudes of 10's-100's of nT within the ocean. Outside of the ocean, the magnitudes are smaller (typically 1-10 nT) but decay on scales set by the horizontal scale of the ocean feature.
We investigate the time-scales associated with the adjustment of electromagnetic fields generated by low-frequency ocean currents. We find that the time scales can be quite long, prohibiting a quasistatic assumption in the treatment of the electromagnetic fields generated by the important tidal, inertial, and diurnal-frequency ocean currents.
Three-dimensional explicit time-dependent and steady-state finite-difference numerical models are constructed to study the electromagnetic fields generated by more realistic ocean current and conductivity features.
The ocean currents generate electromagnetic forces on the fluid at the surface of the earth's core. If these forces lead to significant core motion, the effect of the oceans on the generation and variability of the earth's magnetic field may be nontrivial. We estimate the form and magnitude of these forces and make comparisons with observations. Despite many uncertainties, we find evidence to suggest the ocean forcing mechanism may be significant and conclude that this process should be further investigated in the context of a larger study.
This work indicates that it is likely that the geomagnetic record has captured oceanic signals. From a preliminary data analyses we find that aside from the oceanic tidal signals, the magnetic record shows other signals of possible oceanic origin including an apparent correlation between magnetic records from the equatorial Pacific and the Southern Oscillation Index. We discuss the prerequisites that are necessary to extract information about ocean circulation variability from the geomagnetic record.
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30

Liu, Cheng-Chien. "Using SeaWiFS ocean colour data to test a plankton ecosystem model." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343733.

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31

Cooper, Michael. "A dynamical method for assimilation of altimeter data into ocean models." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/14718.

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A method is developed here for the assimilation of surface restricted satellite data into three dimensional numerical ocean models. Satellite altimetry provides observations of the dynamic topography i.e. the time variations in sea surface height, which provides some constraints on the three dimensional ocean state, but no unique solution. Traditionally, the surface data is projected into the deeper ocean by statistical methods. Here, the pre-analysis model potential vorticity fields are conserved at each analysis, which provides a unique solution for the vertical structure of each model gridpoint when combined with the local sea surface height. The assimilation method is tested in a series of twin experiments, in which the real ocean is substituted by a numerical model run, and limited datasets from this control run are assimilated into another model run with different initial conditions in an attempt to reconstruct the full three-dimensional state of the control run from the surface information alone. The assimilation run fields are then compared with the full control fields in order to determine the success of the assimilation method. Twin experiments with a four layer quasigeostrophic model, and a 21 level primitive equation model show that the typical amount of information available from a single altimeter is sufficient to constrain the full three-dimensional circulation of the ocean model, within the twin experiment framework. The reliance upon dynamically-based conservation laws rather than pre-calculated statistics makes the method computationally cheap and easily portable between models.
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32

Medina, Daniel M. "Real-Time Visualizations of Ocean Data Collected by the NORUS Glider." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/348.

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Scientific visualization computer applications generate visual representations of large and complex sets of science data. These types of applications allow scientists to gain greater knowledge and insight into their data. For example, the visualization of environmental data is of particular interest to biologists when trying to understand how complex variables interact. Modern robotics and sensors have expanded the ability to collect environmental data, thus, the size and variety of these data-sets have likewise grown. Oftentimes, the collected data are deposited into files and databases where they sit in their separate and unique formats. Without easy to use visualization tools, it is difficult to understand and interpret the information within these data-sets. NORUS, the North America-Norway educational program, has a scientific focus on how climate-induced changes impact the living resources and ecosystems in the Arctic. In order to obtain the necessary science data, the NORUS program utilizes the Slocum Glider, a form of Autonomous Underwater Vehicle (AUV). This thesis aims to create a compelling, efficient, and easy to use interactive system for visualizing large sets of science data collected by the Slocum Glider. This goal is obtained through the implementation of various methods taken from scientific visualization, real time rendering, and scattered data interpolation. Methods include visualizations of the surrounding terrain, the ability to map various science data to glyphs, control over color mapping, scattered data interpolation and interactive camera control.
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33

Mantzaris, Demetrios Alexis 1968. "Evaluation of the performance of sailing vessels based on towing tank and sailforce data." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12814.

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34

Li, Dan 1969. "Modeling of monostatic bottom backscattering from three-dimensional volume inhomogeneities and comparisons with experimental data." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43542.

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35

Eucker, William. "A geospatial analysis of Arctic marine traffic." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/248854.

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Recent changes in Arctic Ocean climate dynamics and marine activity in the region require re-evaluation of physical operating conditions, ship traffic patterns, and policy requirements. This study used (1) government surveys, (2) vessel reports, and (3) Automatic Identification System (AIS) messages to characterize the spatial and temporal variability of surface vessel traffic in relation to various sea-ice conditions on the Arctic Ocean during a year-long study from 1 April 2010 to 31 March 2011. Data sources, methods of analysis, and errors were discussed. Three principal topics were examined. First, sea-ice cover on the Arctic Ocean was analysed to determine the physical access for marine operations. Daily sea-ice concentration data based on satellite passive microwave measurements were used to calculate the extent of open water and duration of the sea-ice season. Second, ship traffic on the Arctic Ocean was analysed to determine the present patterns of human activity. Time-stamped AIS messages encoded with Global Navigation Satellite System (GNSS) positions received by a commercial satellite constellation from north of the Arctic Circle (66·56°N) were used to calculate the distribution of vessels per unit area. Satellite AIS data from SpaceQuest, Limited, were compared with land-based vessel observations during the study period from the Marine Exchange of Alaska and the Port of Longyearbyen. Third, the spatial and temporal relationship between sea ice and surface vessels on the Arctic Ocean was analysed to determine potential policy implications. Three groups of marine operations with distinct characteristics were determined from the analysis: operations in perennial open water, operations in the seasonal ice zone, and operations in the perennial ice zone. Throughout the study year, most ships north of 66·56°N operated in perennially icefree areas, but year-round operations also occurred in ice-covered areas. The results from this study identify new pathways of information to enable consistent pan-Arctic assessment of physical operating conditions and ship traffic patterns. This approach provides novel considerations to sustainably develop a safe, secure, and environmentally protected Arctic Ocean.
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36

Weaver, Anthony T. "On assimilating sea surface temperature data into an ocean general circulation model." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29204.

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The feasibility of sea surface temperature (SST) data improving the performance of an ocean general circulation model (OGCM) is investigated through a series of idealized numerical experiments. The GFDL Bryan-Cox-Semtner primitive equation model is set-up as an eddy resolving, unforced, flat bottomed channel of uniform depth. 'Observed' SST data taken from a reference ocean established in a control run are continuously assimilated into an 'imperfect' model using a simple 'nudging' scheme based on a surface relaxation condition of the form Q = C(SST — T₁) where Q is the heat flux and T₁ is the temperature at the top level of the model. The rate of assimilation is controlled by adjusting the constant inverse relaxation time parameter C. Numerical experiments indicate that the greatest improvement in the model fields is achieved in the extreme case of infinite assimilation (i.e., C = ᅇ) in which the 'observed' SST is directly inserted into the model. This improvement is quantified by monitoring the reduction in the root mean square (RMS) errors relative to the simulated reference ocean. Assimilation with longer relaxation time-scales (i.e., smaller C's) proves quite ineffective in reducing the RMS errors. The improvement in the direct insertion numerical experiment stems from the model's ability to transfer assimilated SST into subsurface information through strong advective processes. The assimilation of cool surface data induces convective overturning which transfers the 'cool' information downward rapidly but adversely affects the vertical thermal structure by an unrealistic deepening of the mixed layer. By contrast, warm surface data do not penetrate downward readily. Thus, the systematically biased downward flux of coolness gradually produces unrealistically cool subsurface waters.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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37

Matear, Richard James. "Circulation of the Northeast Pacific Ocean inferred from temperature and salinity data." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27594.

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The temperature, salinity, and pressure (STP) data were collected during two cruises, one in early October and the other in early December of 1987, as part of the Ocean Storms experiment. These hydrographic data were analyzed to determine circulation of the northeast Pacific Ocean and to calculate the factors influencing the heat and salt content of the upper ocean. From the depth profiles of the temperature and salinity data, the water mass in the Ocean Storms area was classified as being the Eastern Sub-Arctic Pacific Water Mass. Maps of dynamic height for this area revealed that the current pattern was generally smooth but that mesoscale eddies did exist in the flow. Isentropic analysis of the temperature and salinity fields produced a flow pattern that was generally consistent with the. dynamic height maps. However, this analysis revealed additional details in the flow that were not evident in the dynamic height maps. To extract additional information from the temperature and salinity data an inverse model was developed. This model assumed that the flow was geostrophic and that the vertical velocity satisfied a linear β-plane vorticity equation. This inverse model calculated the vertical and horizontal velocities at a reference level of 1000 dbars, and the horizontal and vertical mixing terms by conserving mass, salt, and heat. These conservation constraints were applied to large- boxes defined by four hydrographic stations and two pressure surfaces. The circulation determined using the model showed well-defined flow features. Comparison of the absolute geostrophic flow with the seven-day averaged current meter observations showed much similarity, despite complications from an incident storm. Correlation between the geostrophic flow at the surface and the total flow field inferred from drifter data was also high. An estimate of the ageostrophic flow suggested that acceleration and nonlinear terms played an important role in affecting the flow field during the first cruise. The observed change in salt content of the upper 150 m of the ocean was .004 ppt for the sixty days between the two cruises. The net transport of salt into the study area by the calculated flow field was -.016 ppt. Therefore, to balance the salt budget would require E - P = 9 cm. The upper ocean lost 92 W/m² of heat during the sixty days between the two cruises. As the vertical and horizontal transport of heat acounted for 40 W/m² loss of heat, the remainder of heat lost, 52 W/m² was attributed to air-sea boundary processes.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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38

Sears, Timothy John. "Elastic full waveform inversion of multi-component ocean-bottom cable seismic data." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613186.

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39

Troccoli, Alberto. "Ocean data assimilation using the temperature-salinity relation and water mass diagnostics." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/14580.

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In this thesis a novel method for assimilating upper ocean temperature profiles with salinity adjustments into numerical ocean models is presented. The approach uses a T-S relation more local in space and time than the climatological T-S used in previous studies. The assimilation method also avoids convective instability as the temperature data are introduced. In order to test the method, three sets of experiments are carried out. First, Conductivity-Temperature-Depth measurements in the western tropical Pacific, and also instantaneous fields from an ocean model, are used to test the assimilation method by combining one profile with another. These tests recover the salinity profiles and the 0-500-m dynamic height very well (differences smaller than 1 dyn cm). By contrast, analyses using a climatological T-S relation did not provide a good salinity profile or dynamic height (greater than 3 dyn cm errors). Second, a synthetic assimilation experiment using a 3-D primitive equation model is carried out. Four runs are considered: the truth (Tr), the parallel (Pa) and two assimilation runs, one in which the salinity method is applied (AST) and the other in which salinity is left unmodified during the temperature assimilation (ASZ). The only difference between Pa and Tr is that Pa is forced by a wind stress 15% larger than Tr, so as to simulate a systematic observational error. AST and ASZ use the same forcings as Pa. Vertical temperature profiles down to a depth of 525 m are taken as synthetic data from Tr and assimilated every 30 days for two years into AST and ASZ. Results show that AST yields better salinity analyses than both Pa and ASZ, which, in terms of rms errors, translate into at least 15% improvement at the end of the 2-year experiment. In addition to assessing the success of the assimilation method (e.g. using T and S rms), a more physical analysis of the model modifications, due to the assimilation, is presented.
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40

Kosempa, Michael. "Southern Ocean Transport by Combining Satellite Altimetry and Temperature/Salinity Profile Data." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6658.

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Zonal geostrophic velocity fields above 1975 dbar have been estimated for the Southern Ocean from 2004 to 2014 based on sea surface topography observed by Jason altimetry and temperature/salinity measured by Argo autonomous floats. The velocity at 1000 dbar estimated has been validated against Argo drift trajectory at the same pressure level available from the Asia Pacific Data Research Center (APDRC). Errors in mapping of dynamic ocean topography, temperature, and salinity have been quantified using the Southern Ocean State Estimate (SOSE). Analysis of errors reveals significant correlations between depth-dependent and –independent contributions to the integrated transport. Further analysis revealed optimal locations of historical ship casts to compliment the transport time series as observed by Argo. Quantifying the error associated with the historical hydrographic section indicated little benefit in combining hydrographic data obtained from ships. The anticorrelation between depth-dependent and – independent contributions was again significant in sampling by ships. The proposed explanation of the anticorrelation in error is underestimation of reference velocity by attenuation and overestimation of depth-dependent transport by attenuation of the velocity shear.
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41

Holmberg, Edward A. IV. "Data Visualization to Evaluate and Facilitate Targeted Data Acquisitions in Support of a Real-time Ocean Forecasting System." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1873.

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A robust evaluation toolset has been designed for Naval Research Laboratory’s Real-Time Ocean Forecasting System RELO with the purpose of facilitating an adaptive sampling strategy and providing a more educated guidance for routing underwater gliders. The major challenges are to integrate into the existing operational system, and provide a bridge between the modeling and operative environments. Visualization is the selected approach and the developed software is divided into 3 packages: The first package is to verify that the glider is actually following the waypoints and to predict the position of the glider for the next cycle’s instructions. The second package helps ensures that the delivered waypoints are both useful and feasible. The third package provides the confidence levels for the suggested path. This software’s implementation is in Python for portability and modularity to allow for easy expansion for new visuals.
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42

Cunningham, Stuart Andrew. "Circulation and volume flux of the North Atlantic using synoptic hydrographic data in a Bernoulli Inverse." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366422.

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43

Luerssen, Remy Martin. "Relationships between Oceanographic Satellite Data and Alexandrium Distributions in the Gulf of Maine." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/LuerssenRM2001.pdf.

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44

Mathers, Eunice Lucy. "Sea level response to atmospheric pressure and wind forcing in the global deep ocean." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367977.

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45

Gerber, Markus. "Assimilating ocean tracer data into the Bern3D model using an ensemble kalman filter /." [S.l.] : [s.n.], 2009. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.

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46

Tokmakian, Robin Telrud. "The assimilation of satellite altimeter data into a global eddy resolving ocean model." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA333483.

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Dissertation (Ph.D. in Physical Oceanography)--Naval Postgraduate School, June 1997.
Dissertation supervisor: Semtner, Albert J. Includes bibliographical references (p. 165-168). Also Available online.
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47

Campbell, Jeffrey William. "Evaluation of GEOSAT data and application to variability of the northeast Pacific Ocean." Thesis, Cambridge, Massachusetts : Massachusetts Institute of Technology : Woods Hole Oceanographic Institution, 1988. http://hdl.handle.net/10945/23215.

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CIVINS
Part of the N.E. Pacific was studied to evaluate and use altimetric data from the Navy Geodetic Satellite GEOSAT. The zero-order accuracy of the major GEOSAT geophysical data record (GDR) channels was verified, and occasional gaps in the altimeter coverage were noted. GEOSAT's 17-day repeat orbit allowed use of collinear-track processing to create profiles of the difference between the sea surface height along a given satellite repeat, and the mean sea surface height along that repeat's groundtrack. Detrending of sea surface bias and tilt on each repeat reduced orbit and other long wavelength errors in the difference profiles. Corrections provided on the GEOSAT GDR were examined for their effects on the difference profiles of three test arcs. It was found that only the ocean tide, electromagnetic bias, and inverted barometer corrections varied enough over the arc lengths (approx. 4400 km) to have any noticeable effect on the difference profiles. Only the ocean tide correction was accurate enough to warrant using it to adjust the sea surface heights. Recommended processing of GEOSAT data for the area included making the ocean tide correction, three-point block averaging successive sea surface heights, and forming the mean height profiles from 18 repeat cycles (to reduce aliasing of the M2 tidal component), A set of difference profiles for one GEOSAT arc indicated that a reasonable estimate of GEOSAT's system precision was approx. 4.5 cm (RMS). The mid wavelength range (100-500 km) of these profiles was found to be the only range in which oceanic mesoscale features could be separated from altimeter errors
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48

Campbell, Jeffrey William. "Evaluation of GEOSTAT data and application to variability of the Northeast Pacific Ocean." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/51465.

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49

Gunson, James Reginald. "Time-dependent assimilation of CTD data to an open ocean Rossby wave model." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/52962.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1993.
Includes bibliographical references (leaves 66-68).
by James Reginald Gunson.
M.S.
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50

Grey, Stephen M. "Analysis and assimilation of temperature and altimetry data in the North Atlantic Ocean." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/13954.

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Observations of subsurface temperatures in the North Atlantic between 1950 and 1994 have been analysed to investigate interdecadal variability. Previous studies have concentrated on the more plentiful sea surface temperature data or on limited hydrographic data. Here, all subsurface temperature data, principally from bathythermographs, are used to investigate the development and evolution of temperature anomalies. During most of the period, a dipole feature was seen. The western subtropical gyre and the ocean north of 50°N were occupied by anomalies of opposite sign. These regions appear to show a cycle of warming and cooling with a period of approximately 30 years but the data record is too short to determine whether this is a regular oscillation. There is evidence of propagation of temperature anomalies along the paths of the major upper ocean currents, namely along the Gulf Stream and North Atlantic Current and also along the return currents on the southern edge of the subtropical gyre. An intense warm anomaly on the northern edge of the subtropical gyre developed between 1988 and the end of the data in 1994. The Gulf Stream front became steeper and isotherms were depressed by up to 150m. This is consistent with a stronger Gulf Stream and an intensification of the circulation of the subtropical gyre. This is compared with a cold anomaly in 1966-1972 which is opposite in nature, indicating a weaker subtropical gyre circulation. A scheme developed by Cooper and Haines (1996) has been employed to assimilate sea level anomaly data from the TOPEX/POSEIDON altimeter with a climatological hydrography of the North Atlantic.
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