Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 141-148)

The transport of low-salinity waters through the Canadian Arctic Archipelago links the North Pacific, Arctic, and North Atlantic Oceans. This transport is influenced by many related small-scale processes including mixing, internal hydraulics, and internal tide generation. In this thesis, I quantify and elucidate the physics of such processes with aims of addressing discrepancies between observed and simulated fluxes through the Archipelago and advancing the skill of numerical models by identifying shortcomings and informing where and how progress can be achieved. To address the dearth of mixing rates across the network of channels, I first use a large-scale model to obtain baseline estimates of the spatial and seasonal variability of the vertical buoyancy flux. Much of the mixing occurs in the eastern half of the Archipelago and is attributed to the abundance of sills and narrow channels. Indeed, the so-called 'central sills area' is shown to be a mixing hot spot. I investigate this region further using high-spatial-resolution observational transects to examine the role of tides, which are excluded from the large-scale model. The many shallow channels here accelerate tidal currents and thereby induce strong bottom boundary layer dissipation. This is the largest energy sink within an observationally constrained energy budget. The generation of internal tides is another primary sink of barotropic tidal energy. Because the study site lies poleward of the critical latitudes of the dominant tidal constituents, internal tides propagate as internal Kelvin waves. Idealized, process-oriented modelling demonstrates that the amplitudes of such waves, or similarly the energy extracted from the barotropic tide, is sensitive to channel width because waves generated at each side of the channel interfere. Given the multiple connecting channels of the Archipelago, it is difficult to make a priori estimates of internal tide generation for a given channel. Nevertheless, the phenomenology I describe will be detectable in, and a requisite to understanding, pan-Arctic or global three-dimensional tidal models, which are becoming more prevalent. / Graduate

Les instabilités inertielles sont des instabilités fluides excitées au sein de modèles physiques simplifiés de planètes ou d'étoiles. Elles peuvent générer un champ magnétique dynamo. Ce sont donc des alternatives aux écoulements forcés par la convection thermo-chimique pour générer les champs magnétiques dans les noyaux liquides des planètes et les enveloppes fluides des étoiles. Cependant, ces modèles simplifiés questionnent la pertinence des résultats, qui sont ensuite extrapolés aux contextes géo- et astrophysique. D'un point de vue fondamental, de récentes études numériques et expérimentales, réalisées à grande ellipticité pour compenser l'importance des effets visqueux dans les modèles, semblent en désaccord avec les prédictions théoriques (valides dans la limite asymptotique d'une diffusion négligeable et à faible déformation). De plus, de nombreux effets physiques sont négligés dans les modèles. Par exemple, seules les orbites circulaires ont été considérées. Bien que généralement de faible amplitude, l'excentricité induit une dépendance temporelle dans le forçage orbital, ce qui pourrait générer de nouveaux phénomènes. Enfin, l'existence des instabilités inertielles dans les enveloppes fluides stablement stratifiées en densité, comme les zones radiatives des étoiles chaudes de masse intermédiaire (dont la masse est comprise entre une et huit masses solaires), reste incertaine. La génération de champs magnétiques dynamos dans ces enveloppes stratifiées permettrait de réconcilier les modèles avec les observations astronomiques. Lors de cette thèse, nous nous sommes attachés à rapprocher les modèles (théoriques, numériques ou expérimentaux) des contextes géo et astrophysique. Nous avons combiné les approches théoriques (analyses de stabilité locale et globale) et numériques (simulations non linéaires) afin d'étudier les effets des forc cages mécaniques de rotation dans un ellipsoïde fluide. Nous montrons que la dissipation en volume n'est en fait pas négligeable dans les expériences de laboratoire et les simulations numériques, contrairement aux régimes planétaires et stellaires. Nous montrons aussi que l’excentricité orbitale peut, via la variation temporelle des axes de l’ellipsoïde, générer des instabilités fluides pour dans une gamme de paramètres où elles n’étaient pas attendues. Enfin nous avons étudié la capacité dynamo de l'instabilité de marée, dans les enveloppes stablement stratifiées en densité des étoiles chaudes de masse intermédiaire. Environ 10~% de ces étoiles ont un champ magnétique de surface, dont l’origine reste énigmatique. Nous montrons que l’instabilité de marée peut générer des dynamos de grande échelle dans les enveloppes fluides stablement stratifiées. En particulier, ce mécanisme serait susceptible d’expliquer le champ magnétique de faible intensité des étoiles en rotation rapide similaires à Vega et déformées par un compagnon orbital. / Inertial instabilities are fluid instabilities excited by mechanical forcings (e.g. tides, precession) in fluid bodies (e.g. planetary liquid cores or stellar envelopes) orbited by celestial companions. The nonlinear outcome of these instabilities can drive self-sustained, dynamo magnetic fields. Thus they could be an alternative to thermo-chemical convection to generate magnetic fields in geophysics and astrophysics. These instabilities have only been studied in idealised models, which challenges the extrapolation towards the relevant regimes in geophysics and astrophysics. Recent laboratory and numerical studies, performed in the achievable range of parameters (i.e. large deformations and overestimated diffusive effects), seem apparently not in agreement with theoretical predictions representative of celestial fluid bodies (i.e. extremely small deformations and vanishing diffusive effects). Several physical ingredients have been also neglected, such as the orbital eccentricity. This could drive additional tidal effects, as a result of the time-dependent forcing. Similarly, density variations have been largely neglected in these models. However, rotationally powered magnetic fields in stably stratified stellar envelopes could reconcile astronomical observations with dynamo models. In this thesis we have adopted more realistic models, by combining theoretical tools (linear stability analyses in unbounded and bounded fluids enclosed in ellipsoids) and numerical ones (direct numerical simulations) to study rotationally driven inertial instabilities. We show, with a linear stability analysis in bounded ellipsoidal geometry, that bulk diffusion cannot be neglected emph{a priori} compared to the boundary layer diffusion in laboratory experiments and simulations. This phenomena is not expected in celestial fluid bodies. We also show that an orbital eccentricity could generate additional instabilities in deformed bodies, for orbital configurations which were believed to be linearly stable. Finally, we have studied the dynamo capability of tidal flows in stably stratified fluid envelopes. These are idealised models of hot, intermediate-mass stars (i.e. with a mass ranging from one to eight solar masses). Approximatively 10~% of hot stars exhibit observable magnetic fields. We show that the tidal instability can drive dynamo magnetic fields of large wavelength in stably stratified fluids. Predictions obtained with this tidal model seem consistent with the ultra-weak magnetism of rapidly rotating, tidally deformed Vega-like stars.

Made available in DSpace on 2014-06-11T19:24:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-07Bitstream added on 2014-06-13T18:51:55Z : No. of bitstreams: 1 pinto_jv_me_guara.pdf: 1385196 bytes, checksum: 8f4e005504bfa301a50295aa1563c0d7 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / Aplicações recentes de satélites artificiais da Terra com finalidades geodinâmicas requerem órbitas determinadas com bastante precisão. Em particular, marés terrestres influenciam o potencial terrestre causando perturbações adicionais no movimento de satélites artificiais, as quais têm sido medidas por diversos processos. A atração exercida pela Lua e pelo Sol sobre a Terra produz deslocamentos elásticos em seu interior e uma protuberância em sua superfície. O resultado é uma pequena variação na distribuição da massa na Terra, conseqüentemente alterando o geopotencial. As perturbações nos elementos orbitais de satélites artificiais terrestres devidas à maré terrestre podem ser estudadas a partir das equações planetárias de Lagrange, considerando-se um potencial conveniente. Alguns modelos têm sido propostos para o cálculo de perturbações orbitais devidas à maré, tais como os modelos de Kaula, de Kozai, de Balmino e o utilizado pelo IERS. Os resultados encontrados na literatura são, em geral difíceis de serem comparados, pois os cálculos são feitos com diferentes modelos. Neste trabalho são apresentadas, para os potenciais mencionados, as expressões analíticas em forma expandida. Alguns cenários são propostos mostrando, para tais modelos, as diferenças nas perturbações de longo período e seculares, nos elementos orbitais de satélites artificiais, devidas á maré terrestre. / Recent applications of artificial Earth's satellites, as for instance with geodynamics purposes, require very high precision orbit determination. In particular, terrestrial tides affects the geopotential causing additional orbital perturbations that can be measured by several methods. The Sun and Moon attraction on the Earth produces both an elastics displacements in the Earth's interior and a bulge in its surface. The resulting effect is a small variation in the Earth's mass distribution. The perturbations in the orbital elements due to the terrestrial tides can be analysed using the Lagrange planetary equations considering a convenient potential. Some models have been proposed to compute orbital perturbations due to the terrestrial tides, such as the models proposed by Kozai, Kaula, Balmino and the model used by the IERS. The results found in the literature about orbit perturbations due to terrestrial tides were obtained using different models being difficult to be compared. In this work the above-referred models are presented. Expanded analytical expressions are presented. Some scenarios are proposed showing, for such models, the differences in the secular and long period perturbations of the orbital elements, due to the terrestrial tides.

Orientador: Rodolpho Vilhena de Moraes / Banca: Maria Cecília França de Paula Santos Zanardi / Banca: Hélio Koiti Kuga / Resumo: Aplicações recentes de satélites artificiais da Terra com finalidades geodinâmicas requerem órbitas determinadas com bastante precisão. Em particular, marés terrestres influenciam o potencial terrestre causando perturbações adicionais no movimento de satélites artificiais, as quais têm sido medidas por diversos processos. A atração exercida pela Lua e pelo Sol sobre a Terra produz deslocamentos elásticos em seu interior e uma protuberância em sua superfície. O resultado é uma pequena variação na distribuição da massa na Terra, conseqüentemente alterando o geopotencial. As perturbações nos elementos orbitais de satélites artificiais terrestres devidas à maré terrestre podem ser estudadas a partir das equações planetárias de Lagrange, considerando-se um potencial conveniente. Alguns modelos têm sido propostos para o cálculo de perturbações orbitais devidas à maré, tais como os modelos de Kaula, de Kozai, de Balmino e o utilizado pelo IERS. Os resultados encontrados na literatura são, em geral difíceis de serem comparados, pois os cálculos são feitos com diferentes modelos. Neste trabalho são apresentadas, para os potenciais mencionados, as expressões analíticas em forma expandida. Alguns cenários são propostos mostrando, para tais modelos, as diferenças nas perturbações de longo período e seculares, nos elementos orbitais de satélites artificiais, devidas á maré terrestre. / Abstract: Recent applications of artificial Earth's satellites, as for instance with geodynamics purposes, require very high precision orbit determination. In particular, terrestrial tides affects the geopotential causing additional orbital perturbations that can be measured by several methods. The Sun and Moon attraction on the Earth produces both an elastics displacements in the Earth's interior and a bulge in its surface. The resulting effect is a small variation in the Earth's mass distribution. The perturbations in the orbital elements due to the terrestrial tides can be analysed using the Lagrange planetary equations considering a convenient potential. Some models have been proposed to compute orbital perturbations due to the terrestrial tides, such as the models proposed by Kozai, Kaula, Balmino and the model used by the IERS. The results found in the literature about orbit perturbations due to terrestrial tides were obtained using different models being difficult to be compared. In this work the above-referred models are presented. Expanded analytical expressions are presented. Some scenarios are proposed showing, for such models, the differences in the secular and long period perturbations of the orbital elements, due to the terrestrial tides. / Mestre

Le but de cette étude était de développer une méthodologie pour évaluer la résilience des littoraux aux évènements de tempêtes, à des échelles de temps différentes pour une plage située à une latitude moyenne (Biscarrosse, France). Un site pilote des tropiques, la plage de Jamestown (Ghana), non soumis aux tempêtes, a également été analysé. 6 ans (2007-2012) de données sur la position du trait de côte,obtenues quotidiennement par imagerie vidéo, ainsi que les prévisions hydrodynamiques (ECMWF EraInterim) ont été analysées. Le climat de vagues est dominé par les tempêtes (Hs> 5% de seuil de dépassement) et leurs fluctuations saisonnières; 75% des tempêtes se produisent en hiver, et plus de 60tempêtes ont été identifiées au cours de la période d'étude. Une régression multiple, montre qu’alors que les intensités des tempêtes actuelle et précédente ont un rôle majeur sur l'impact de la tempête, la marée et les barres sableuses jouent un rôle majeur sur la récupération de plage. La position moyenne du trait de côte calculée sur la période de récupération post-tempête montre que la plage de Biscarrosse se reconstruit rapidement (9 jours) après un évènement isolé et que les séries de tempêtes (clusters) ont un effet cumulatif diminué. Les résultats indiquent que le récurrence individuelle des tempêtes est clé. Si l'intervalle entre deux tempêtes est faible par rapport à la période de récupération, la plage devient plus résistante aux tempêtes suivantes; par conséquent, la première tempête d’une série a un impact plus important que les suivantes. Le trait de côte répond, par ordre décroissant, aux évènements saisonniers,à la fréquence des tempête et aux d’échelle annuelle. La méthode EOF montre de bonnes capacité à séparer la dynamique « uniforme » et « non-uniforme » du littoral et décrit différentes variabilités temporelles: les échelles saisonnières et à court terme dominent, respectivement, la première EOF (2D)et le second mode (3D). Le littoral de Jamestown a été étudié comme base d’un projet pilote entre 2013-2014. Les fluctuations du niveau de l'eau jouent un rôle prédominant sur l’évolution de la position du trait de côte. Les vagues et les estimations des marées obtenues par l’exploitation d’images vidéo sont corrélées avec les données de prévisions. Cette étude pionnière montre que cette technique peut être généralisée à toute l’Afrique de l'Ouest en tenant compte des multiples diversités et de la variabilité du climat régional, à travers un réseau d'observations. / The aim of this study was to develop a methodology to statistically assess the shorelineresilience to storms at different time scales for a storm-dominated mid-latitude beach(Biscarrosse, France). On a pilot base, storm-free tropical Jamestown beach (Ghana) was alsoanalysed. 6-years (2007-2012) of continuous video-derived shoreline data and hindcastedhydrodynamics were analysed. Wave climate is dominated by storms (Hs>5% exceedancelimit) and their seasonal fluctuations; 75% of storms occur in winter with more than 60identified storms during the study period. A multiple regression on 36 storms shows thatwhereas current and previous storm intensity have predominant role on current storm impact,tide and sandbar play a major role on the post-storm recovery. An ensemble average on poststormrecovery period shows that Biscarrosse beach recovers rapidly (9 days) to individualstorms, and sequences of storms (clusters) have a weak cumulative effect. The results point outthat individual storm recurrence frequency is key. If the interval between two storms is lowcompared to the recovery period, the beach becomes more resilient to the next storms; and thefirst storm in clusters has larger impact than following ones. Shoreline responds in decreasingorder at seasonal, storm frequency and annual timescales at Biscarrosse. The EOF methodshows good skills in separating uniform and non-uniform shoreline dynamics, showing theirdifferent temporal variability: seasonal and short-term scales dominate first EOF (2D) andsecond (3D) modes, respectively.The shoreline at Jamestown was studied on pilot base from 2013-2014. Water level channgesplay a major role on shoreline changes. Waves estimates from video are in good agreement withhindcasts. This study shows the potential of the technique, to be replicated elsewhere in WestAfrica with all its diversity and regional climate variability through a coastal observationnetwork.

Studies were carried out to determine the circulation of water in the northern basin of Howe Sound, a small fjord on the mainland coast of British Columbia, and to determine the extent of the influence of the winds, the tide and river runoff on the circulation. In one experiment, surface-layer drogues were tracked by radar for four periods each of approximately three days duration. Data sere recorded photographically, then digitized for computer processing. Cubic spline interpolation was used to produce positions, velocities and accelerations at one minute intervals along every drogue track. The interpolated data were averaged in a suitable manner to produce pseudo-Eulerian estimates of velocity. Near the head of the fjord, both wind and tide appeared to cause temporal fluctuations in the surface current of magnitude similar to the expected mean flow due to the river. The river was the cause of spatial inhomogeneity in the flow, but did not appear to be a significant source of temporal variations. Farther down the inlet, wind forcing was the dominant cause of temporal variations in the surface-layer flow of about five times the magnitude of the expected mean river-driven flow. At no distance along the fjord was the velocity observed to be laterally uniform. Lateral gradients of long-channel velocity were strong at the inlet head and decreased away from it, indicating that the fresh water from the river was slowly mixing across the inlet. Another experiment using drogues at three depths in the upper 6 m of the water indicated that the velocity structure was not uniform, either laterally or with depth. Analysis was done on data from six current meters moored in the northern basin of Howe Sound. The mean currents from these meters showed a surface-layer outflow and a return inflow in the waters just below. A mean down-inlet current was seen at 150 m, 80 m below sill depth. Spectra of the currents showed dominant peaks at diurnal and semi-diurnal periods. The wind was coherent with the currents at 3m for periods longer than 10 hours. Below this depth, no consistent relationship was seen. In the diurnal band, the currents were strongest at the surface, indicative of forcing from the surface by the wind. In the semi-diurnal band, the currents were strongest at 10m depth. Both bands also showed a phase variation with depth indicative of a baroclinic structure. These results were compared with some models for surface-layer behaviour. The first model assumed that the wind momentum input was distributed uniformly throughout the surface layer and that the layer was not frictionally coupled to the deeper waters. Drag coefficients calculated from the wind stress and drogue acceleration gave values of 1 to 2x10-3, similar to values measured in other ways. This model was only valid for the first few hours after the onset of the wind. Another model, developed by Farmer (1972), analysed the behaviour of the surface layer of a semi-infinite canal under the influence of a steady wind stress. It predicted correctly the length of time of wind dominance of the flow, the magnitude of the velocity change and the magnitude of the acceleration of the water. A baroclinic tidal model in a two-layer fjord, adapted from Rattray (1960), correctly predicted the phase of the surface-layer currents near the head of a fjord with respect to the height of the tide. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Orientador: Cristiano de Mello Gallep / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-22T03:28:54Z (GMT). No. of bitstreams: 1 Moraes_ThiagoAlexandre_M.pdf: 12211625 bytes, checksum: 5e27e2aac5dfc12de0ee782b7b6a33bc (MD5) Previous issue date: 2013 / Resumo: A emissão fotônica ultrafraca proveniente de plântulas de trigo foi mensurada em várias séries de testes sob condições constantes, no interior de câmara escura. Grãos brasileiros também foram transportados e testados na Alemanha, em séries simultâneas realizadas paralelamente a séries conduzidas tanto no Brasil quanto na Alemanha. As plântulas em ambos os países apresentaram ritmos semicircadianos, coincidentes e em sincronia com os ritmos da variação da aceleração gravimétrica local, produzidos pelos movimentos lunissolares. São apresentadas análises matemáticas a respeito destas sincronias e coincidências. Em mais de 80% do período de testes considerados o coeficiente local de correlação de Pearson entre os dois parâmetros revelou relação significante (P>0,7). Com o uso da transformada rápida de Fourier foram evidenciadas as similaridades entre as componentes temporais de oscilação do parâmetro fotônico e as encontradas no parâmetro gravimétrico. As fases da lua e a época do ano possivelmente produzem influências relevantes no desenvolvimento das plântulas. Os resultados encontrados sustentam a hipótese de que os processos envolvidos com a emissão fotônica em plântulas de trigo sejam regulados pelos ritmos de variação gravimétrica, produzidos pelos movimentos lunissolares. A técnica de detecção de emissão fotônica espontânea se mostrou uma ferramenta inovadora e útil para estudos biofísicos e cronobiológicos / Abstract: The ultra-weak photon emission from wheat seedling was measured in several series of tests under constant conditions inside a dark chamber. Brazilian seeds were also transported and tested in Germany, with simultaneous series conducted both in Brazil and in Germany. The seedlings showed, in both countries, semi-circadian rhythms coincident and in synchrony with the rhythms of local gravimetric variations of acceleration produced by lunisolar movements. Mathematical analysis of these synchronies and coincidences are presented. The local Pearson correlation coefficient between the two parameters showed a significant relationship (P> 0.7) in more than 80% of the considered testing period. The rhythmic similarities between the biophotonic oscillation and the gravimetric parameter were done by fast Fourier transform. The phases of the moon and the time of year possibly produce relevant influences on development of seedlings. The results support the hypothesis that processes involved with biophoton emission in wheat seedlings may be regulated by variations on the gravimetric rhythms in accordance to lunisolar movements. Further studies are desirable in order to look for the physiological origin of this phenomenon. The spontaneous ultra-weak photon emission detection technique proved to be a new and useful tool for chrono-biological and biophysical studies / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia

Cette thèse étudie les mécanismes de dissipation de marée dans les étoiles de faible masse, possédant comme notre Soleil une enveloppe convective externe (i.e. de types M à F), ainsi que dans les planètes géantes gazeuses similaires à Jupiter et Saturne. En particulier, nous cherchons à comprendre et à caractériser l’influence de la structure et de la dynamique internes de ces corps sur les différents mécanismes physiques à l’origine de cette dissipation afin d’évaluer leur importance relative.Dans le cas des planètes géantes, nous utilisons des modèles semi-analytiques préexistants et nous montrons que la dissipation induite par la présence éventuelle d’un cœur solide viscoélastique n’est pas négligeable par rapport à celle induite par les ondes inertielles (dont la force de rappel est l’accélération de Coriolis) dans l’enveloppe convective. Pour les étoiles de faible masse, nous développons de nouvelles méthodes semi-analytiques ainsi que des simulations numériques d’ondes inertielles de marée se propageant dans l’enveloppe convective externe, dont nous calculons et caractérisons la dissipation d’énergie associée. Pour la première fois, nous prenons en compte les effets d’une rotation différentielle latitudinale telle qu’observée dans le Soleil et prédite par de nombreuses simulations numériques de convection dans les étoiles de faible masse. Nous mettons en évidence l’existence de nouvelles familles de modes inertiels ainsi que l’importance des résonances de corotation pour la dissipation de marée. Enfin, nous dérivons une nouvelle prescription pour la viscosité turbulente appliquée à ces ondes de marées en prenant en compte l’influence de la rotation sur les propriétés de la convection le long de l’évolution des étoiles. / This thesis studies the tidal dissipation mechanisms in low-mass stars that have an external convective envelope like the Sun (i.e. from M- to F-type stars), as well as in Jupiter- and Saturn-like gaseous giant planets. We particularly focus on understanding and characterizing the influence of the internal structure and dynamics of these bodies on the various physical mechanisms that cause this tidal dissipation, in order to assess their relative strength.In the case of giant planets, we use preexisting semi-analytical models and we show that the dissipation induced by the possible presence of a viscoelastic solid core is not negligible compared to the one induced by inertial waves (whose restoring force is the Coriolis acceleration) in the convective envelope. For low-mass stars, we perform a new semi-analytic study as well as numerical simulations of tidal inertial waves propagating in the external convective envelope, and we compute the associated energy dissipation. For the first time, the effects of a background latitudinal differential rotation, as observed in the Sun and predicted by various numerical simulations of convection in low-mass stars, is taken into account. We highlight the existence of new families of inertial modes as well as the importance of corotation resonances for tidal dissipation. Finally, we derive a new prescription for the turbulent viscosity applied to these tidal waves that takes into account the influence of rotation on the properties of convective flows along the evolution of stars.

No description available.