Dissertations / Theses on the topic 'Variability of the surface salinity'
To see the other types of publications on this topic, follow the link: Variability of the surface salinity.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Variability of the surface salinity.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Sommer, Anna. "Salinité de surface dans le gyre subtropical de l'Atlantique Nord (SPURS/SMOS/Mercator)." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066436/document.
Full textAbstract:
Ce travail a porté sur la variabilité de la salinité de surface (SSS) de l'océan dans le gyre subtropical Nord Atlantique. J'ai étudié la variabilité saisonnière de la SSS en lien avec les flux d'eau douce échangés avec l'atmosphère et la circulation océanique à méso échelle, au cours de plus de deux ans, d'août 2012 à décembre 2014. Les produits issus de la mission satellitaire soil moisture and ocean salinity (SMOS) corrigés de biais systématiques aux grandes échelles ont été testés et utilisés pour restituer la variabilité méso-échelle de SSS. Nous avons de surcroit utilisé les simulations numériques à haute résolution PSY2V4R2-R4 de Mercator. Les champs issus de SMOS et des simulations ont été comparés aux données in situ de bouées dérivantes et de thermosalinographes recueillies pendant l'expérience SPURS, avec des résultats satisfaisants, en particulier en hiver, et des écarts-type de différences typiques de l'ordre de 0.15 pss. Le flux d’eau douce échangé avec l’atmosphère est le terme dominant dans le bilan saisonnier de la SSS. Ce sont des termes associés à la dynamique océanique qui le compensent partiellement. En particulier, l’entrainement des eaux sous-jacentes contribue fortement en début d’hiver. Il agit d’ordinaire à réduire la SSS, à l’exception de la région au sud du maximum de SSS, où c’est au contraire une augmentation qu’il induit. L’advection est une seconde contribution importante à la variabilité de la SSS. Elle transfert ainsi vers le nord les eaux ‘salinisées’ plus au sud dans la région du maximum de perte d’eau douce vers l’atmosphère. La contribution d'advection est fortement dépend du type de données utilisées et leur résolution spatialeThe focus of this work is on sea surface salinity (SSS) variability in the North Atlantic subtropical gyre. We study seasonal SSS variability and its link to the atmospheric freshwater flux at the ocean surface and to ocean dynamics at meso-scales for the period August 2012 – December 2014. The products from the soil moisture and ocean salinity (SMOS) satellite mission corrected from large scale systematic errors are tested and used to retrieve meso-scale salinity features. Furthermore, the PSY2V4R2-R4 simulation produced by Mercator with a high spatial resolution is also used. The comparison of corrected SMOS SSS data and Mercator simulation with drifter's in situ and TSG measurements from the SPURS experiment shows a reasonable agreement with RMS differences on the order of 0.15 pss.The freshwater seasonal flux is the leading term in the SSS seasonal budget. To balance its effect the ocean dynamics strongly contribute. The entrainment of deeper water is strong during the winter time. It usually acts to lower SSS, except in the south of the SSS–max region where it contributes to increase salinity. Advection is the second important component responsible for the SSS variability. It transfers further north the salty water from the evaporation maximum region. The contribution of advertion term is strongly dependent on the type of data used and their spatial resolution
2
Tonin, Hemerson E., and hemer tonin@flinders edu au. "Atmospheric freshwater sources for eastern Pacific surface salinity." Flinders University. Chemistry, Physics and Earth Sciences, 2006. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20061031.080144.
Full textAbstract:
The remarkable salinity difference between the upper Pacific and Atlantic Oceans is often explained through net export of water vapour across Central America. To investigate this mechanism a study of salinity signals in the Equatorial Pacific Ocean current system was made looking at responses to fresh water input from two sources (local versus remote - Atlantic Ocean) as well as a combination of the two. Statistical analyses (Empirical Orthogonal Functions, Single Value Decomposition and Wavelet analysis) were used to split the main sources of the atmospheric freshwater input into local and remote contributions and to quantify both contributions. The remote source was assumed to have been transported over Central America from the Atlantic Ocean as an atmospheric freshwater flux, whereas the local source originated in the Pacific Ocean itself. The analysis suggests that 74% of the total variance in precipitation over the tropical eastern Pacific is due to water vapour transport from the Atlantic. It also demonstrates strong influence of ENSO events, with maximum correlation at a two months time lag. During La Ni�a periods the precipitation variance is more closely related to water vapour transport across Central America (the remote source), while during El Ni�o periods it is more closely related to the water vapour transport by Southerly winds along the west coast of South America (the local source). The current and temperature fields provided by the Modular Ocean Model (version 2) were used to study the changes in the salinity field when freshwater was added to or removed from the model. ECMWF ERA-40 data taken from the ECMWF data server was used to determine the atmospheric flux of freshwater at the ocean surface, in the form of evaporation minus precipitation (E-P). The Mixed Layer Depth (MLD) computed from temperature and salinity fields determines to what depth the salinity's dilution/concentration takes place for every grid point. Each MLD was calculated from the results of the previous time step, and the water column was considered well mixed from the surface to this depth. The statistical relationships were used to reconstruct the precipitation over the tropical eastern Pacific. A numerical ocean model, which uses currents and temperature from a global ocean model and is forced by precipitation, was used to study the ocean's response to either the remote or the local source acting in isolation. Through time lag correlation analysis of the sea surface salinity anomalies produced by the variation in the reconstructed precipitation fields, it is found that the anomaly signals of salinity propagate westward along the Equator at a rate of approximately 0.25 m.s-1 (6.1 degrees per month).
3
Nurhati, Intan Suci. "Coral records of central tropical Pacific sea-surface temperature and salinity variability over the 20th century." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34775.
Full textAbstract:
Accurate forecasts of future regional temperature and rainfall patterns in many regions largely depend on characterizing anthropogenic trends in tropical Pacific climate. However, strong interannual to decadal-scale tropical Pacific climate variability, combined with sparse spatial and temporal coverage of instrumental climate datasets in this region, have obscured potential anthropogenic climate signals in the tropical Pacific. In this dissertation, I present sea-surface temperature (SST) and salinity proxy records that span over the 20th century using living corals from several islands in the central tropical Pacific. I reconstruct the SST proxy records via coral Sr/Ca, that are combined with coral oxygen isotopic (d18O) records to quantify changes in seawater d18O (hereafter d18Osw) as a proxy for salinity.
Chapter 2 investigates the spatial and temporal character of SST and d18Osw-based salinity trends in the central tropical Pacific from 1972-1998, as revealed by corals from Palmyra (6ºN, 162ºW), Fanning (4ºN, 159ºW) and Christmas (2ºN, 157ºW) Islands. The late 20th century SST proxy records exhibit warming trends that are larger towards the equator, in line with a weakening of equatorial Pacific upwelling over this period. Freshening trends revealed by the salinity proxy records are larger at those sites most affected by the Inter-Tropical Convergence Zone (ITCZ), suggesting a strengthening and/or an equatorward shift of the ITCZ. Taken together, the late 20th century SST and salinity proxy records document warming and freshening trends that are consistent with a trend towards a weakened tropical Pacific zonal SST gradient under continued anthropogenic forcing.
Chapter 3 characterizes the signatures of natural and anthropogenic variability in central tropical Pacific SST and d18Osw-based salinity over the course of 20th century using century-long coral proxy records from Palmyra. On interannual timescales, the SST proxy record from Palmyra tracks El Niño-Southern Oscillation (ENSO) variability. The salinity proxy record tracks eastern Pacific-centered ENSO events but is poorly correlated to central Pacific-centered ENSO events - the result of profound differences in precipitation and ocean advection that occur during the two types of ENSO. On decadal timescales, the coral SST proxy record is significantly correlated to the North Pacific Gyre Oscillation (NPGO), suggesting that strong dynamical links exist between the central tropical Pacific and the North Pacific. The salinity proxy record is significantly correlated to the Pacific Decadal Oscillation (PDO), but poorly correlated to the NPGO, suggesting that, as was the case with ENSO, these two modes of Pacific decadal climate variability have unique impacts on equatorial precipitation and ocean advection. However, the most striking feature of the salinity proxy record is a prominent late 20th century freshening trend that is likely related to anthropogenic climate change. Taken together, the coral data provide key constraints on tropical Pacific climate trends, and when used in combination with model simulations of 21st century climate, can be used to improve projections of regional climate in areas affected by tropical Pacific climate variability.
4
Whitaker, Jessica L. "Orbital- to millennial-scale variability in Gulf of Mexico sea surface temperature and salinity during the late Pleistocene." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002550.
Full text
5
Köhler, Julia [Verfasser], and Detlef [Akademischer Betreuer] Stammer. "Sea Surface Salinity Variability and Underlying Mechanisms : an analysis and interpretation of satellite data / Julia Köhler. Betreuer: Detlef Stammer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1095766341/34.
Full text
6
Köhler, Julia Verfasser], and Detlef [Akademischer Betreuer] [Stammer. "Sea Surface Salinity Variability and Underlying Mechanisms : an analysis and interpretation of satellite data / Julia Köhler. Betreuer: Detlef Stammer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1095766341/34.
Full text
7
Nababan, Bisman. "Bio-optical variability of surface waters in the Northeastern Gulf of Mexico." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001104.
Full text
8
Korkmaz, Muhtesem Akif. "The Impact Of Climate Variability On The Physical Properties Of The Black Sea For The Period 1971." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613737/index.pdf.
Full textAbstract:
Deep ventilation of the Black Sea is inhibited by a sharp salinity gradient within the upper water column, resulting in a shallow anoxic interface at around 100 &ndash200 m depth. Understanding biological and chemical processes within the boundary region between oxic and anoxic waters is fundamental to comprehend the biogeochemical response of the Black Sea to climate forcing. The structure and depth of the chemocline is largely determined by the physical processes which transport surface waters to depth. Here we investigate how the structure and stability of the upper water column responds to changes in climatic forcing over interannual to multidecadal time-scales. We report results from two hydrodynamic model reanalysis. The first, extending from 1971-1993 assimilates CTD data. The second, extending from 1992-2001, assimilates altimetry data. Model results are validated against CTD and satellite data and consistency between modeled surface properties and observations is demonstrated. A problem with the data assimilation scheme of the 1992 -2001 model run is identified, which results in model drift and an unrealistic water column structure at intermediate depths. Model results indicate a warming trend of 0.7 °
C in sea surface temperature and a freshening trend of 0.4 in sea surface salinity between 1971 and 2001, with an associated increasing trend in the stability of the seasonal thermocline and a declining trend in surface mixed layer depth of 6.3 m. Trends are superimposed on a distinct multiannual variability characterized by relatively warm and saline conditions between 1971 and 1984, relatively cool and fresh conditions between 1985 and 1993 and warm and fresh conditions post-1993. The period between 1985 and 1993 corresponds to higher NAO and EA/WR index values although these indices do not exhibit a similar ~decadal scale variability. Higher frequency interannual variability in water column characteristics is related to the NAO and EA/WR atmospheric indices. Despite the cool conditions prevalent during the 1990s, the persistent freshening trend caused a reduction in the density of mixed layer waters throughout the study period. A positive feedback is proposed between increasing SSTs, reduced vertical mixing and freshening of the surface layer which further increases the stability of the upper water column. CIL characteristics typically mirrored surface temperature characteristics and varied considerably between the relatively warm period during the early part of the study and the subsequent cool period. The mean thickness and temperature of the CIL between 1971 and 1981 were ~39 m and ~7.5 °
C respectively, as compared to ~47 m and ~7.4 °
C between 1982 and 1993. Freshening of the upper water column also resulted in an increase in the stability maxima that exists at the base of the CIL, suggesting reduced ventilation of the upper water column during winter.
9
Awo, Founi Mesmin. "Modes interannnuels de la variabilité climatique de l'Atlantique tropical, dynamiques oscillatoires et signatures en salinité de surface de la mer." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30171/document.
Full textAbstract:
Dans cette thèse, nous avons abordé plusieurs thématiques liées aux modes de variabilité climatique dans l'Atlantique tropical à l'échelle interannuelle. Les analyses statistiques nous ont permis dans un premier temps de mettre en évidence les deux principaux modes dominants de cette variabilité interannuelle: un mode équatorial et un mode méridien. Le mode équatorial est responsable d'anomalies de température de surface de la mer (SST) principalement dans le Golfe de Guinée et est identifié par des variations de la pente du niveau de la mer dans la bande équatoriale. Il est dû à des rétroactions dynamiques entre le vent, le niveau de la mer et la SST. Quant au mode méridien, il se manifeste par des fluctuations inter-hémisphériques de SST et est contrôlé par des rétroactions dynamiques et thermodynamiques entre le vent, l'évaporation et la SST. L'évaluation du couplage de ces variables clés du mode méridien nous a permis de proposer un modèle conceptuel pour expliquer les principaux mécanismes responsables des oscillations du mode méridien. Le modèle a montré que le mode méridien résulte de la superposition d'un mécanisme auto-entretenu basé sur les rétroactions positives et négatives générant des oscillations régulières de haute fréquence (2-3 ans) et d'un autre mécanisme d'oscillation basse fréquence (4-9 ans) lié à l'influence d'ENSO du Pacifique Est. Comme l'évolution de ces deux modes est fortement liée au déplacement méridien de la zone de convergence intertropicale (ITCZ) qui transporte les pluies, nous avons ensuite identifié la signature de ces modes sur la salinité de la surface de la mer à l'aide observations in situ et d'une simulation numérique régionale. Les processus océaniques et/ou atmosphériques responsables de la signature de chaque mode ont été également identifiés grâce à un bilan de sel dans la couche de mélange du modèle validé. Le bilan de sel a révélé que le forçage atmosphérique, lié à la migration de l'ITCZ, contrôle la région équatoriale tandis que l'advection, due à la modulation des courants, du gradient vertical et le mélange à la base de la couche de mélange, explique les variations de SSS dans les régions sous l'influence des panaches. [...]In this thesis, we investigate several topics related to the interannual climatic modes in the tropical Atlantic. Statistical analyses allows us to extract the two main dominant modes of interannual variability: an equatorial mode and a meridional mode. The equatorial mode is responsible for Sea Surface Temperature (SST) anomalies mainly found in the Gulf of Guinea and is linked to variations of the sea-level slope in the equatorial band. It is due to dynamic feedbacks between zonal wind, sea level and SST. The meridional mode is characterised by inter-hemispheric SST fluctuations and is controlled by dynamic and thermodynamic feedbacks between the wind, evaporation and SST. After quantifying the coupling between key variables involved in the meridional mode, we develop a conceptual model to explain the main mechanisms responsible for meridional mode oscillations. The model shows that the meridional mode results from the superposition of a self-sustaining mechanism based on positive and negative feedbacks generating regular oscillations of high frequency (2-3 years) and another low frequency oscillation mechanism (4-9 years) related to the influence of ENSO. As the evolution of these two modes is strongly linked to the meridional shift of the Intertropical Convergence Zone (ITCZ) and associated rainfall maximum, we identify the signature of these modes on Sea Surface Salinity (SSS) using in situ observations and a regional numerical simulation. Oceanic and/or atmospheric processes responsible for the signature of each mode are also identified through a mixed-layer salt budget in the validated model. The salt balance reveals that the atmospheric forcing, related to the ITCZ migration, controls the equatorial region while the advection, due to the modulation of current dynamics, the vertical gradient and mixing at the base of the mixed layer, explains SSS variations in regions under the influence of plumes. Finally, we study the Equatorial Kelvin wave characteristics and influences on the density that are involved in the meridional and equatorial mode connection processes, using a very simplified model of gravity wave propagation along the equator. After a brief description of this model, which was initially constructed to study dynamics in the equatorial Pacific, we apply it to the specific case of the equatorial Atlantic by validating its analytical and numerical solutions under adiabatic conditions. [...]
10
Michel, Sylvain. "Télédétection de la salinité à la surface des océans : variabilité de la salinité de surface d'après un modèle global de couche mélangée océanique." Paris 7, 2006. http://www.theses.fr/2006PA077206.
Full textAbstract:
En préparation du satellite SMOS de l'ESA, nous proposons une méthode pour estimer la salinité de surface des océans (SSS) à partir des observations satellitaires actuelles. Un modèle simplifié de couche mélangée océanique, basé sur la formulation "slab mixed layer" (Frankignoul et Hasselmann, 1977), est implémenté sur l'océan global avec une résolution proche de 100 km et intégré au cours d'une année climatologique. La profondeur de la couche mélangée (MLD), dérivée des observations de température de surface (SST) grâce à une technique d'inversion originale, est bien corrélée aux estimations basées sur des données in situ. Cette profondeur effective représente la pénétration des flux air-mer et assure la cohérence entre les flux, les courants et la SST. La simulation est d'abord validée en examinant le bilan de chaleur dans l'Atlantique Nord-Est, par comparaison aux mesures et aux modèles de l'expérience POMME. Puis le bilan de salinité est étudié dans le domaine global, en termes de distribution géographique et d'évolution saisonnière. L'équilibre entre les différents processus est généralement plus complexe que pour la température : le flux atmosphérique est moins prépondérant (22%), tandis que l'advection géostrophique (33%) et le mélange diapycnal (22%) contribuent fortement. Ce modèle restitue la variabilité de la SSS sur la majeure partie des océans et simule les variations journalières de SSS, qui ne sont pas représentées à l'échelle globale dans les observations actuelles. Grâce à sa simplicité et à sa rapidité, le modèle pourra aider à la calibration/validation de SMOS et fournir une estimation a priori pour l'algorithme de restitution de la SSSTo contribute to ESA's SMOS mission, we propose a method for estimating sea surface salinity (SSS) from current satellite observations and for studying the mechanisms governing ils variability. A simplified model of the ocean mixed layer, based on the "slab mixed layer" formulation (Frankignoul et Hasselmann, 1977), is implemented over the global ocean, using a near 100 km resolution, and integrated during a climatological year. The mixed layer depth (MLD), derived from surface temperature (SST) observations using an original inversion technique, is well correlated to in situ estimates. This effective depth represents the air-sea fluxes penetration and ensures consistency between fluxes, currents and SST. We first validate the simulation through examination of the heat budget in the north-eastern Atlantic, by comparing to measurements and models from the POMME experiment. Then we study the salinity budget in the global domain, in terms of its geographical distribution and seasonal evolution. The balance between the various processes appears generally more complex than for temperature: the role of atmospheric flux is less predominant (22%), while geostrophic advection (33%) and diapycnal mixing (22%) contribute more strongly. The model succeeds in reconstructing SSS variability over most of the oceans and simulates daily SSS variations, which are not represented in current observed data at a global scale. Owing to its simplicity and fast computation, the model will help for the calibration/validation of SMOS measurement and provide a first guess estimate to the SSS restitution algorithm
11
Hénocq, Claire. "Préparation de l’étalonnage et de la validation des mesures de salinité SMOS : de l’influence de la stratification verticale de la salinité." Paris 6, 2009. https://tel.archives-ouvertes.fr/tel-00471532.
Full textAbstract:
L’objectif du satellite européen SMOS (Soil Moisture and Ocean Salinity), lancé le 02 novembre 2009, est de mesurer par radiométrie en bande L la salinité de surface des océans (SSS) et l’humidité des sols. Pour atteindre une précision de 0. 1 – 0. 2 pss sur des cartes de SSS moyennées sur 10 jours et sur 200 km x 200 km, une phase d’étalonnage et de validation des mesures doit être réalisée. Une des techniques retenues est la comparaison entre des salinités in situ, mesurées à plusieurs mètres de profondeur et les salinités SMOS, représentatives du premier centimètre sous la surface océanique. Cette différence de profondeur peut engendrer des biais de salinité importants, notamment en cas de fortes précipitations. Cette thèse, réalisée en collaboration avec le LOCEAN et ACRI-St se concentre sur la variabilité verticale de la salinité dans les 10 premiers mètres de la couche de surface océanique et ses conséquences pour la phase d’étalonnage/ validation de SMOS. Elle propose, à partir de mesures in situ, une description des différences verticales de salinité sur l’ensemble des zones océaniques tropicales (30°N – 30°S). Une étude statistique de la relation entre ces différences verticales et un paramètre de pluie, construit à partir des mesures satellitaires de taux de précipitation est également effectuée. Pour combler le manque de mesures in situ de salinité proche de la surface, j’ai également étudié la possibilité d’utiliser des modèles théoriques pour simuler les différences verticales de salinité en cas de pluie : le modèle de circulation océanique NEMO et le modèle unidimensionnel PWP ([Price et al. , 1986]) qui calcule la profondeur de la couche de mélange.
12
Stuebe, David Allen. "Temperature and salinity variability in thermohaline staircase layers." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/39194.
Full textAbstract:
Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2005.Includes bibliographical references (p. 65-67).
A moored profiler record from the western tropical North Atlantic provides the first continuous time series of temperature, salinity and velocity profiles in a thermohaline staircase. Variations in the intensity of layering and the evolution of layer properties are well documented during the 4.3 month record. Such staircases are the result of strong salt fingering at the interfaces between the mixed layers, and these data provide unique insights into the dynamics of salt fingers. In particular, a striking linear correlation between the temperature and salinity of the layers may be interpreted as resulting from vertical salt finger flux divergences. Data from this record allow new interpretations of previous work on this topic by McDougall (1991).
by David Allen Stuebe.
S.M.
13
Mignot, Juliette. "Sur la variabilité climatique de la salinité de surface en Atlantique Nord et son lien avec la circulation océanique dans un modèle couplé." Paris 6, 2003. https://tel.archives-ouvertes.fr/tel-00005370.
Full text
14
Hasson, Audrey. "Étude diagnostique de la variabilité de la salinité de surface de l'Océan Pacifique : apport des données SMOS." Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2645/.
Full textAbstract:
La salinité est un paramètre essentiel de l'océan car elle impacte les processus océaniques de la sous-meso échelle à l'échelle du bassin et interannuelle. Son rôle a été souligné dans la dynamique du phénomène El Nino ainsi que dans le déplacement de masses d'eaux telles que les eaux intermédiaires subtropicales et les eaux profondes. Elle est considérée comme une Variable Climatique Essentielle par l'Organisation Météorologique Mondiale. La distribution du sel dans l'océan est le résultat d'un équilibre subtil entre le forçage de surface (évaporation, précipitation et ruissellement), l'advection horizontale de sel et les échanges avec la sub-surface (entrainement et mélange), chacun de ces termes étant d'égale importance. Même si ces processus sont connus de façon qualitative, quantifier l'effet de chacun d'entre eux est toujours une question ouverte. Cette thèse a pour but de : a) quantifier les mécanismes responsables de la variabilité de la salinité de surface dans l'Océan Pacifique tropical (principalement aux échelles saisonnières et interannuelles), b) décrire et évaluer les processus à l'origine des variations de salinité de surface pendant l'évènement La Nina de 2010-2011 et c) analyser la formation et la variabilité du noyau de maximum de sel de l'Océan Pacifique subtropical (aux mêmes échelles de temps). Différents jeux de données sont utilisés conjointement : des observations de salinité in situ (bateaux marchands, profileurs Argo. . . ), des données de salinité de surface dérivées du nouveau satellite SMOS et d'autres produits issus de mesures satellitaires (précipitations, évaporation et courants de surface) ainsi qu'une simulation spécifique d'un modèle forcéSalinity is one of the key parameters of the ocean impacting its dynamics through density. It is considered as an Essential Climate Variable. The salinity patterns result from a subtle balance between surface forcing (E-P, Evaporation minus Precipitation), horizontal salt advection (at low and high frequencies) and subsurface forcing (entrainment and mixing), all terms being of analogous importance. While processes responsible for sea surface salinity (SSS) changes are qualitatively well known, quantifying those mechanisms is very challenging and hence still under debate. My Ph. D. Research work aims at: a) quantifying mechanisms responsible for the tropical Pacific Ocean SSS variability (mainly at seasonal and ENSO time scale), b) describing and assessing mechanisms behind the 2010-2011 La Niña SSS changes, and c) analysing the formation and variability of the south Pacific subtropical high SSS core (at the same time scales). In order to do so, various datasets are used conjointly: in-situ salinity observations mainly from voluntary observing ships and Argo profilers, satellite based surface salinity (from SMOS), precipitation, evaporation and near-surface currents as well as a specific forced model simulation
15
Da-Allada, Casimir. "La salinité de la couche de surface océanique dans l'océan Atlantique tropical : variabilités saisonnière à interannuelle." Phd thesis, Université Paul Sabatier - Toulouse III, 2013. http://tel.archives-ouvertes.fr/tel-00925720.
Full textAbstract:
Pour étudier la variabilité de la salinité de surface (SSS) dans l'océan Atlantique tropical aux échelles de temps saisonnières à interannuelles, nous avons utilisé des observations in-situ et satellitaires et des résultats de la modélisation océanique. Nous avons montré que la densité et la qualité des observations disponibles permettent de calculer le bilan de sel dans la couche de mélange dans le bassin Atlantique tropical. Ce bilan de sel de la couche de mélange est beaucoup plus sensible aux courants de surface qu'aux flux d'eau douce. Les mécanismes qui modulent la variabilité de la SSS dans l'Atlantique tropical et plus spécifiquement dans la région du Golfe de Guinée ont été déterminés. Il ressort qu'à l'ouest et au nord-est du bassin tropical, la variabilité saisonnière de la SSS est pilotée par l'advection et les flux d'eau douce alors qu'au centre du bassin, c'est principalement les flux d'eau douce qui contrôlent le bilan de sel. Par contre, dans le Golfe de Guinée, les flux d'eau douce ne jouent pas un grand rôle dans le bilan de sel, le cycle saisonnier de la SSS résultant en un équilibre entre les processus verticaux (advection et diffusion) qui augmentent la SSS et l'advection horizontale qui la diminue. La variabilité interannuelle de la SSS étudiée spécifiquement dans le Golfe de Guinée révèle que, dans les régions nord et équatoriale, les changements de SSS sont dus à des changements des précipitations et d'évaporation et les changements dans les processus océaniques (advection et diffusion verticale). Au sud de ces régions, seuls les changements dans les processus océaniques peuvent expliquer les anomalies de SSS. On a observée une salinisation au nord-est du Golfe de Guinée durant la période 2002-2009 qui résulte principalement d'une diminution des pluies dans la région. Enfin, nous avons montré que les fleuves ont pour rôle d'amplifier le signal de la SSS et qu'ils ont un impact sur la profondeur de la couche de mélange, les courants de surface et la température de surface de la mer.
16
Da-Allada, Casimir Yélognissè. "La salinité de la couche de surface océanique dans l'océan atlantique tropical : variabilités saisonnière à interannuelle." Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2150/.
Full textAbstract:
Pour étudier la variabilité de la salinité de surface (SSS) dans l'océan Atlantique tropical aux échelles de temps saisonnières à interannuelles, nous avons utilisé des observations in-situ et satellitaires et des résultats de la modélisation océanique. Nous avons montré que la densité et la qualité des observations disponibles permettent de calculer le bilan de sel dans la couche de mélange dans le bassin Atlantique tropical. Ce bilan de sel de la couche de mélange est beaucoup plus sensible aux courants de surface qu'aux flux d'eau douce. Les mécanismes qui modulent la variabilité de la SSS dans l'Atlantique tropical et plus spécifiquement dans la région du Golfe de Guinée ont été déterminés. Il ressort qu'à l'ouest et au nord-est du bassin tropical, la variabilité saisonnière de la SSS est pilotée par l'advection et les flux d'eau douce alors qu'au centre du bassin, c'est principalement les flux d'eau douce qui contrôlent le bilan de sel. Par contre, dans le Golfe de Guinée, les flux d'eau douce ne jouent pas un grand rôle dans le bilan de sel, le cycle saisonnier de la SSS résultant en un équilibre entre les processus verticaux (advection et diffusion) qui augmentent la SSS et l'advection horizontale qui la diminue. La variabilité interannuelle de la SSS étudiée spécifiquement dans le Golfe de Guinée révèle que, dans les régions nord et équatoriale, les changements de SSS sont dus à des changements des précipitations et d'évaporation et les changements dans les processus océaniques (advection et diffusion verticale). Au sud de ces régions, seuls les changements dans les processus océaniques peuvent expliquer les anomalies de SSS. On a observé une salinisation au nord-est du Golfe de Guinée durant la période 2002-2009 qui résulte principalement d'une diminution des pluies dans la région. Enfin, nous avons montré que les fleuves ont pour rôle d'amplifier le signal de la SSS et qu'ils ont un impact sur la profondeur de la couche de mélange, les courants de surface et la température de surface de la merThe objective of this thesis is to study the variability of the ocean sea surface salinity (SSS) in the tropical Atlantic Ocean, at seasonal and interannual time scales. To achieve this, we used in-situ and satellite data as well as results of ocean models. We have shown that the density and the quality of the available observations allows us to approach the salinity balance in the mixed-layer in the whole tropical Atlantic basin and mixed-layer salinity balance is more sensitive to currents than to freshwater flux. We investigate the main mechanisms which modulate the variability of the SSS in the tropical Atlantic and especially in the Gulf of Guinea. In the western and north-eastern tropical Atlantic Ocean, the seasonal variability of SSS is controlled by advection and freshwater flux whereas, in the central basin, the salinity balance is mostly due to freshwater flux. In the Gulf of Guinea, freshwater flux does not play a key role as in previous regions and the seasonal cycle of SSS is a balance between the vertical processes (advection and diffusion) that increase SSS and the horizontal advection which decrease the SSS. We focus our analysis of SSS interannual variability in the Gulf of Guinea. Results indicate that in the northern region and in the equatorial region, SSS changes are due to changes in precipitations and evaporation and changes in oceanic processes (advection and vertical diffusion) while in the southern Gulf of Guinea only oceanic process changes can explain SSS anomalies. We noted an SSS increase in the northeastern Gulf of Guinea during the period 2002-2009. We argue that it is due mainly to decrease precipitation in this region. Finally, we also showed that the effect of the runoff is to amplify the signal of SSS and can impact the mixed layer depth, the surface currents and the sea surface temperature
17
Sabia, Roberto. "Sea surface salinity retrieval error budget within the esa soil moisture and ocean salinity mission." Doctoral thesis, Universitat Politècnica de Catalunya, 2008. http://hdl.handle.net/10803/30542.
Full textAbstract:
L’oceanografia per satèl•lit ha esdevingut una integració consolidada de les tècniques convencionals de monitorització in situ dels oceans. Un coneixement precís dels processos oceanogràfics i de la seva interacció és fonamental per tal d’entendre el sistema climàtic. En aquest context, els camps de salinitat mesurats regularment constituiran directament una ajuda per a la caracterització de les variacions de la circulació oceànica global. La salinitat s’utilitza en models oceanogràfics predictius, pero a hores d’ara no és possible mesurar-la directament i de forma global.
La missió Soil Moisture and Ocean Salinity (SMOS) (en català, humitat del sòl i salinitat de l’oceà) de l’Agència Espacial Europea pretén omplir aquest buit mitjançant la implementació d’un satèl•lit capaç de proveir aquesta informació sinòpticament i regular.
Un nou instrument, el Microwave Imaging Radiometer by Aperture Synthesis (MIRAS) (en català, radiòmetre d’observació per microones per síntesi d’obertura), ha estat desenvolupat per tal d’observar la salinitat de la superfície del mar (SSS) als oceans a través de l’adquisició d’imatges de la radiació de microones emesa al voltant de la freqüència de 1.4 GHz (banda L). SMOS portarà el primer radiòmetre orbital, d’òrbita polar, interferomètric 2D i es llençarà a principis de 2009.
Així com a qualsevol altra estimació de paràmetres geofísics per teledetecció, la recuperació de la salinitat és un problema invers que implica la minimització d’una funció de cost. Per tal d’assegurar una estimació fiable d’aquesta variable, la resta de paràmetres que afecten a la temperatura de brillantor mesurada s’ha de tenir en compte, filtrar o quantificar. El producte recuperat seran doncs els mapes de salinitat per a cada passada del satèl•lit sobre la Terra.
El requeriment de precisió proposat per a la missió és de 0.1 ‰ després de fer el promig en finestres espaciotemporals de 10 dies i de 20x20.
En aquesta tesi de doctorat, diversos estudis s’han dut a terme per a la determinació del balanç d’error de la salinitat de l’oceà en el marc de la missió SMOS. Les motivacions de la missió, les condicions de mesura i els conceptes bàsics de radiometria per microones es descriuen conjuntament amb les principals característiques de la recuperació de la salinitat.
Els aspectes de la recuperació de la salinitat que tenen una influència crítica en el procés d’inversió són:
• El biaix depenent de l’escena en les mesures simulades,
• La sensibilitat radiomètrica (soroll termal) i la precisió radiomètrica,
• La definició de la modelització directa banda L
• Dades auxiliars, temperatura de la superfície del mar (SST) i velocitat del vent, incerteses,
• Restriccions en la funció de cost, particularment en el terme de salinitat, i
• Promig espacio-temporal adequat.
Un concepte emergeix directament de l’enunciat del problema de recuperació de la salinitat: diferents ajustos de l’algoritme de minimització donen resultats diferents i això s’ha de tenir en compte. Basant-se en aquesta consideració, la determinació del balanç d’error s’ha aproximat progressivament tot avaluant l’extensió de l’impacte de les diferents variables, així com la parametrització en termes d’error de salinitat.
S’ha estudiat l’impacte de diverses dades auxiliars provinents de fonts diferents sobre l’error SSS final. Això permet tenir una primera impressió de l’error quantitatiu que pot esperar-se en les mesures reals futures, mentre que, en un
altre estudi, s’ha investigat la possibilitat d’utilitzar senyals derivats de la reflectometria per tal de corregir les incerteses de l’estat del mar en el context SMOS.
El nucli d’aquest treball el constitueix el Balanç d’Error SSS total. S’han identificat de forma consistent les fonts d’error i s’han analitzat els efectes corresponents en termes de l’error SSS mig en diferents configuracions
d’algoritmes.
Per una altra banda, es mostren els resultats d’un estudi de la variabilitat horitzontal de la salinitat, dut a terme utilitzant dades d’entrada amb una resolució espacial variable creixent. Això hauria de permetre confirmar la capacitat de la SSS recuperada per tal reproduir característiques oceanogràfiques mesoscàliques.
Els principals resultats i consideracions derivats d’aquest estudi contribuiran a la definició de les bases de l’algoritme de recuperació de la salinitat.Satellite oceanography has become a consolidated integration of conventional in situ monitoring of the oceans. Accurate knowledge of the oceanographic processes and their interaction is crucial for the understanding of the climate system. In this framework, routinely-measured salinity fields will directly aid in characterizing the variations of the global ocean circulation. Salinity is used in predictive oceanographic models, but no capability exists to date to measure it directly and globally. The European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) mission aims at filling this gap through the implementation of a satellite that has the potential to provide synoptically and routinely this information. A novel instrument, the Microwave Imaging Radiometer by Aperture Synthesis, has been developed to observe the sea surface salinity (SSS) over the oceans by capturing images of the emitted microwave radiation around the frequency of 1.4 GHz (L-band). SMOS will carry the first-ever, polar-orbiting, space-borne, 2-D interferometric radiometer and will be launched in early 2009. Like whatsoever remotely-sensed geophysical parameter estimation, the retrieval of salinity is an inverse problem that involves the minimization of a cost function. In order to ensure a reliable estimation of this variable, all the other parameters affecting the measured brightness temperature will have to be taken into account, filtered or quantified. The overall retrieved product will thus be salinity maps in a single satellite overpass over the Earth. The proposed accuracy requirement for the mission is specified as 0.1 ‰ after averaging in a 10-day and 2ºx2º spatio-temporal boxes. In this Ph.D. Thesis several studies have been performed towards the determination of an ocean salinity error budget within the SMOS mission. The motivations of the mission, the rationale of the measurements and the basic concepts of microwave radiometry have been described along with the salinity retrieval main features. The salinity retrieval issues whose influence is critical in the inversion procedure are: • Scene-dependent bias in the simulated measurements, • Radiometric sensitivity (thermal noise) and radiometric accuracy, • L-band forward modeling definition, • Auxiliary data, sea surface temperature (SST) and wind speed, uncertainties, • Constraints in the cost function, especially on salinity term, and • Adequate spatio-temporal averaging. A straightforward concept stems from the statement of the salinity retrieval problem: different tuning and setting of the minimization algorithm lead to different results, and complete awareness of that should be assumed. Based on this consideration, the error budget determination has been progressively approached by evaluating the extent of the impact of different variables and parameterizations in terms of salinity error. The impact of several multi-sources auxiliary data on the final SSS error has been addressed. This gives a first feeling of the quantitative error that should be expected in real upcoming measurements, whilst, in another study, the potential use of reflectometry-derived signals to correct for sea state uncertainty in the SMOS context has been investigated. The core of the work concerned the overall SSS Error Budget. The error sources are consistently binned and the corresponding effects in terms of the averaged SSS error have been addressed in different algorithm configurations. Furthermore, the results of a salinity horizontal variability study, performed by using input data at increasingly variable spatial resolution, are shown. This should assess the capability of retrieved SSS to reproduce mesoscale oceanographic features. Main results and insights deriving from these studies will contribute to the definition of the salinity retrieval algorithm baseline.
18
Kelble, Christopher Richard. "The Effect of Salinity Variability on the Mesozooplankton Community of Florida Bay." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/392.
Full textAbstract:
The greater Everglades ecosystem, including Florida Bay, has undergone significant anthropogenic manipulation over the past century. These actions resulted in a series of ecologically undesirable events in the Everglades ecosystem, prompting passage of the Comprehensive Everglades Restoration Plan (CERP). It is necessary to understand the variability in, and relationship between, salinity and ecology to fully evaluate the potential effects of CERP on Florida Bay. A seven-year dataset on surface salinity along with eleven-year and eight-year datasets on mesozooplankton and planktivorous fish were analyzed. Overall, mean Bay-wide salinity varied from a low of 24.2 just after the passing of Hurricane Irene in October 1999 to a high of 41.8 near the end of a drought period in July 2001. Bay-wide mean salinity exhibited dramatic decreases, up to 0.5 per day, whereas increases in bay-wide salinity were slower, with a maximum rate of 0.1 per day. Meteorological phenomena, such as tropical cyclones and ENSO, dramatically altered the salinity patterns of Florida Bay on interannual time scales. There was a large degree of spatial heterogeneity in salinity between sub-regions of Florida Bay due to differing freshwater sources and geomorphology. Mesozooplankton abundance displayed interannual variability and a positive correlation with salinity. Both of these features were also closely correlated with abundance of the dominant planktivorous fish, Anchoa mitchilli, indicating the importance of top-down control. The hypersaline periods appear to provide a refuge from predators, allowing mesozooplankton to increase in abundance during periods of increased physiological stress. The interaction between mesozooplankton and A. mitchilli, along with its correlation to salinity, was further investigated through the development of a mechanistic model of the populations in Florida Bay. The model indicated predation alone was insufficient to control mesozooplankton populations; rather, it was necessary to incorporate density-dependence utilizing a logistic prey population. With both mechanisms the model was able to replicate the observed interannual variability pattern and positive correlation between mesozooplankton and salinity. A preliminary management scenario evaluation suggests a two to six-fold difference in A. mitchilli and mesozooplankton populations between targeted and general salinity reductions. This suggests alternative freshwater management scenarios could produce drastically different ecological consequences.
19
Schlundt, Michael [Verfasser]. "Mixed layer heat and salinity variability in the equatorial Atlantic / Michael Schlundt." Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1052893716/34.
Full text
20
Fidel, Quilanda. "Spatial and temporal variability of coastal temperature and salinity in Angolan waters." Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/6471.
Full textAbstract:
Bibliography: leaves 55-62.To study the coastal hydro-climate in the central Angolan region, in situ temperatrure and satellite derived SST and in situ salinity were used to describe both the SST and SSS fields off Angola during the period 1969-1999 with some gaps. Emphasis was placed upn the Lobito coastal oceanographic station (12° 19S 13° 34E) mean temperature and salinity distributions and the seasonal and interannual temperature and salinity variability. The main aims of this study were thus to identify, quantify and analyze the above parameters and to establish their effects on the appropriate time scales of variability.
21
Talone, Marco. "Contributrion to the improvement of the soil moisture and ocean salinity (SMOS) sea surface salinity retrieval algorithm." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/48633.
Full textAbstract:
The European Space Agency's Soil Moisture and Ocean Salinity (SMOS)
satellite was launched on November, 2, 2009 from the Russian cosmodrome
of Plesetsk. Its objective is to globally and regularly collect measurements of
soil moistre and Sea Surface Salinity (SSS). To do that, a pioneering instru-
ment has been developed: the Microwave Imaging Radiometer by Aperture
Synthesis (MIRAS), the rst space-borne, 2-D interferometric radiometer
ever built; it operates at L-band, with a central frequency of 1.4135 GHz,
and consists of 69 antennas arranged in a Y shape array. MIRAS' output
are brightness temperature maps, from which SSS can be derived through
an iterative algorithm, and using auxiliary information. For each overpass
of the satellite an SSS map is produced, with an estimated accuracy of 1
psu (rmse). According to the Global Ocean Data Assimilation Experiment
(GODAE) the mission requirement is instead speci ed as 0.1 psu after av-
eraging in a 10-day and 2 2 spatio-temporal boxes.
In previuos works ((Sabia et al., 2010), or more extensively in Dr. Sabia's
Ph.D. thesis (Sabia, 2008)) the main error sources in retrieving SSS from
SMOS measurements were determined as:
1. Scene-dependent bias in the simulated measurements,
2. L-band forward modeling de nition,
3. Radiometric sensitivity and accuracy,
4. Constraints in the cost function, and
5. Spatio-temporal averaging.
This Ph.D. thesis, is an attempt of reducing part of the aforementioned
errors (the relative to the one-overpass SSS (1 - 4)) by a more sophisticated
data processing.
Firstly, quasi-realistic brightness temperatures have been simulated using
the SMOS End-to-end Performance Simulator (SEPS) in its full mode and
an ocean model, as provider for geophysical parameters. Using this data
set the External Brightness Temperature Calibration technique has been
tested to mitigate the scene-dependent bias, while the error introduced by
inaccuracies in the L-band forward models has been accounted for by the
application of the External Sea Surface Salinity Calibration.
Apart from simulated brightness temperatures, both External Brightness
Temperature Calibration and External Sea Surface Salinity Calibration have
been tested using real synthetic-aperture brightness temperatures, collected
by the Helsinki University of Technology HUT-2D radiometer during the
SMOS Calibration and Validation Rehearsal Campaign in August 2007 and
ten days of data acquired by the SMOS satellite between July 10 and 19,
2010.
Finally, a study of the cost function used to derive SSS has been performed:
the correlation between measurement mis ts has been estimated and the
e ect of including it in the processing have been assessed.
As an outcome of a 3-month internship at the Laboratoire LOCEAN in
Paris, France, a theoretical review of the e ect of the rain on the very top
SSS vertical pro le has been carried out and is presented as Appendix.
22
Lundmark, Kim. "The spatial variability of salinity and water flux estimates in Gialova Lagoon, Greece." Thesis, Stockholms universitet, Institutionen för naturgeografi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-161341.
Full textAbstract:
Lagoons are coastal waterbodies which are sensitive to meteorological and hydrological changes. This study focused on the spatial distribution of salinity in Gialova lagoon, Greece. The area in which the lagoon is located is under pressure from agriculture and truism in the area. Besides that, the lagoon is an important stop for migratory birds as well as the home for rare species. To investigate how salinity is distributed in the lagoon a salinity gradient was produced. Also, an attempt was made to model the salt and fresh water fluxes in the lagoon using a mass balance approach. The water fluxes are either from fresh water sources or influx of saline water from the sea. Manual electric conductivity measurements were taken during a field campaign to the lagoon. Time series data used in the model was obtained from stations in the lagoon and the surroundings. An investigation in how the lagoon measurement station differ in salinity was also performed in this study. Results from the gradient map and manual measurements show that the water in the lagoon is the freshest in the North-Eastern parts and the most saline to the South-West. The modelled water fluxes show an inverse relationship from each other. High fresh water fluxes correspond to precipitation events, lower salinity concentration. Whereas high salt water fluxes correspond to high salinity concentration and lowered precipitation. The stations concentrated to the middle lagoon show corresponding values in salinity whereas the station to the South-West differs. The canal surrounding the lagoon shows interactions since measurements show that the water is brackish. A longer time series could provide patterns in water fluxes over time. Trying to find the portions of terrestrial groundwater and surface water, and further investigation of the regional aquifer could provide new information to develop this model. The region is expected to experience water stress which makes further studies and monitoring important.
23
Mabey, Deborah L. "Variability of refractivity in the surface layer." Thesis, Monterey, California. Naval Postgraduate School, 2002. http://hdl.handle.net/10945/5877.
Full textAbstract:
The author and members of the Boundary Layer Studies Group collected atmospheric surface layer profile properties affecting RF propagation during the Roughness and Evaporation Duct experiment off the windward coast of Oahu. We measured temperature, humidity and pressure profiles from the surface and up to 100 m by multi-level buoy-mounted sensors and a rawinsonde attached to a kite flown from a small vessel. We obtained the profiles concurrently with S-, X- and Ku-Band propagation measurements along a 26-km path. Using existing surface-layer bulk models, profiles of the gradient of modified refractivity were computed from the buoy data at one level and compared with the actual values obtained from the kite and the buoy. The bulk estimates did not agree well with the buoy data within the lowest 5 m. The kite and buoy data did not show the strong gradients just above the surface that were expected from theory. This same effect was noted when the kite experiment was repeated over much colder water near San Diego, CA. A refractive model was not able to forecast the variability of measured RF propagation characteristics when driven with the merged kite and buoy data. Using bulk estimates did result in some forecast skill.
24
Hejazin, Yazan Henry. "A Microwave Radiometer Roughness Correction Algorithm For Sea Surface Salinity Retrieval." Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5294.
Full textAbstract:
The Aquarius/SAC-D is an Earth Science remote sensing satellite mission to measure global Sea Surface Salinity (SSS) that is sponsored by the NASA and the Argentine Space Agency (CONAE). The prime remote sensor is the Aquarius (AQ) L-band radiometer/scatterometer, which measures the L-band emitted blackbody radiation (brightness temperature) from the ocean. The brightness temperature at L-band is proportional to the ocean salinity as well as a number of physical parameters including ocean surface wind speed. The salinity retrieval algorithm make corrections for all other parameters before retrieving salinity, and the greatest of these is the increased brightness temperature due to roughness caused by surface wind speed. This thesis presents an independent approach for the AQ roughness correction, which is derived using simultaneous measurements from the CONAE Microwave Radiometer (MWR). When the wind blows over the ocean's surface, the brightness temperature is increased because of the ocean wave surface roughness. The MWR provides a semi-empirical approach by measuring the excess ocean emissivity at 36.5 GHz and then applying radiative transfer theory (improved ocean surface emissivity model) to translate this to the AQ 1.4 GHz frequency (L-band). The theoretical basis of the MWR algorithm is described and empirical results are presented that demonstrate the effectiveness in reducing the salinity measurement error due to surface roughness.ID: 031001312; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Linwood Jones.; Title from PDF title page (viewed March 25, 2013).; Thesis (M.S.E.E.)--University of Central Florida, 2012.; Includes bibliographical references (p. 43-44).
M.S.E.E.
Masters
Electrical Engineering and Computing
Engineering and Computer Science
Electrical Engineering
25
Mignot, Juliette. "Sur la variabilité climatique de la salinité de surface en Atlantique Nord et son lien avec la circulation océanique dans un modèle couple." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2003. http://tel.archives-ouvertes.fr/tel-00005370.
Full textAbstract:
L'objet de cette thèse est l'étude du comportement des anomalies de salinité de surface (SSS) dans l'Atlantique. On étudie leurvariabilité aux échelles de temps interannuelles à décennales, leur réponse aux principaux modes de variabilité atmosphérique dans l'Atlantique Nord et leur lien avec la circulation océanique de grande échelle. Etant donné le manque d'observations de SSS sur des longues périodes et à l'échelle du bassin, le travail est essentiellement basé sur des simulations globales couplées. Dans la première partie de la thèse, la dynamique proprement dite des anomalies de SSS est analysée grâce à deux simulations couplées en conditions de contrôle étudiées successivement: le run SINT EX (ECHAM4-OPA8) et le run de contrôle du Bergen Climate Model (ARPEGE-MICOM). Nos résultats montrent que l'advection par les anomalies de courants d'Ekman est en moyenne au moins aussi efficace que le flux d'eau douce pour générer des anomalies de SSS aux échelles de temps intrasaisonnières. Ceci a pu être confirmé dans les observations. Une fois créées, les anomalies de SSS sont relativement persistantes car elles ne sont pas amorties par les flux atmosphériques, au contraire des anomalies de température de surface. Elles sont donc plus fortement influencées par les courants moyens et par la variabilité géostrophique. En fait, ces deux facteurs dominent les changements de SSS à basse fréquence sur la majorité du bassin. En utilisant un outil de calcul de trajectoires lagrangiennes, on a pu suivre en particulier la propagation d'anomalies de SSS le long des courants océaniques moyens pendant au moins 5 ans. L'analyse a été effectuée aussi bien localement que pour la réponse aux principaux modes de variabilité atmosphérique dans l'Atlantique Nord comme l'Oscillation Nord-Atlantique (NAO) et l'East Atlantic Pattern. Les résultats sont similaires. Dans la deuxième partie de la thèse, la variabilité de la circulation méridienne en moyenne zonale est analysée dans le Bergen Climate Model. L'intensification de la convection profonde dans les hautes latitudes de l'Atlantique Nord force une accéleration de la circulation méridienne moyenne avec un délai de 5 ans environ. L'influence de la NAO sur la convection profonde est également mise en évidence mais le lien entre la NAO et la c irculation méridienne se fait principalement par action mécanique du vent et n'est détectable qu'aux échelles de temps interannuelles. Le Pacifique tropical influence quant à lui la variabilité basse fréquence de la circulation méridienne moyenne dans le modèle. Le phénomène El Ni~no crée des anomalies positives de salinité dans l'Atlantique tropical. Celles-ci sont advectées en une trentaine d'années dans les hautes latitudes de l'océan At lantique Nord où elles semblent forcer une accélération de la circulation méridienne moyenne en contribuant à la déstabilisation de la colonne d'eau.
26
Sena, Martins Meike [Verfasser], and Detlef [Akademischer Betreuer] Stammer. "Salinity variability from in situ and satellite retrieved measurements / Meike Sena Martins ; Betreuer: Detlef Stammer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1118724070/34.
Full text
27
Sena, Martins Meike Verfasser], and Detlef [Akademischer Betreuer] [Stammer. "Salinity variability from in situ and satellite retrieved measurements / Meike Sena Martins ; Betreuer: Detlef Stammer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1118724070/34.
Full text
28
Li, Tianshi. "Temporal variability of north Pacific Ocean surface cyclones." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60060.
Full textAbstract:
The temporal variability of North Pacific Ocean surface cyclones is presented, based upon a nine cold-season dataset from the National Meteorological Center. Our results show that: (1) January is the most active month for oceanic cyclone activity; the most active zone of the cyclonic characteristics is at its southernmost location in January; (2) Interannual variability of cyclone activity is pronounced. The interannual variability of cyclone activity is predominantly stronger than the seasonal variability; (3) Analyses of objectively defined regimes, defined on the basis of a 30-day clustering of surface cyclone activity, reveal that regional climatological anomalies of surface cyclone frequency, significant at the 95% level of confidence, can be identified as precursors to the onset of these 30-day circulation regimes.
29
Beaty, Kristen. "Determination of near-surface variability using Rayleigh waves." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0007/MQ59778.pdf.
Full text
30
Lutton, Deborah A. "Variability of surface structure expression in Bacteroides fragilis." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334571.
Full text
31
Wimmer, Werenfrid. "Variability and uncertainty in measuring sea surface temperature." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/359071/.
Full textAbstract:
Sea Surface Temperature (SST) measurement is one of the most easily obtainable climate variables. However, it is challenging to meet the required absolute accuracy and long term stability whether the data are derived by in situ or satellite measurements. This study explores the quality of SST measurements, in particular those derived by the Advanced Along Track Scanning Radiometer (AATSR) and in situ measurements recorded by the shipborne Infrared Sea surface temperature Autonomous Radiometer (ISAR), which are used for validating AATSR data. Its broad objective is to improve understanding of measurement uncertainties in order to quantify the quality of satellite derived SST used for climate records. The uncertainties of in situ measurement by ISAR have been analysed and modelled in order to estimate an independent measurement uncertainty for every SST data point in the ISAR records. In a complementary study the separate uncertainties of the SST as observed by AATSR, ISAR and ship-based hull-mounted thermometry (SSTdepth), when observing the same track, have been resolved by means of three way uncertainty analysis. This not only serves to verify the ISAR uncertainty model but also demonstrates the e�ectiveness of using shipborne radiometry in preference to in water thermometry from ships or buoys for validating satellite SST products. A third area of study concerns the errors and uncertainties when comparing satellite and in situ observations, which result from failure to properly match the in situ observations to what the satellite \sees". A new method has been developed for classifying the \match-up quality" of each data pair. Its use is demonstrated to show that the quality of AATSR data may be better than classical validation match
32
White, Cary Blake, and Cary Blake White. "Soil Moisture Variability in Land Surface-Atmosphere Interactions." Thesis, The University of Arizona, 1996. http://hdl.handle.net/10150/626791.
Full textAbstract:
Meteorological measurements in the Walnut Gulch catchment in Arizona were used
to synthesize a distributed, hourly-average time series of data across a 26.9 by 12.5 km area
with a grid resolution of 480 m for a continuous 18-month period which included two
seasons of monsoonal rainfall. Coupled surface-atmosphere model runs established the
acceptability (for modeling purposes) of assuming uniformity in all meteorological variables
other than rainfall. Rainfall was interpolated onto the grid from an array of 82 recording rain
gauges. These meteorological data were used as forcing variables for an equivalent array of
stand-alone Biosphere-Atmosphere Transfer Scheme (BATS) models to describe the
evolution of soil moisture and surface energy fluxes in response to the prevalent,
heterogeneous pattern of convective precipitation. The calculated area-average behavior was
compared with that given by a single aggregate BATS simulation forced with area-average
meteorological data. Heterogeneous rainfall gives rise to significant but partly compensating
differences in the transpiration and the intercepted rainfall components of total evaporation
during rain storms. However, the calculated area-average surface energy fluxes given by the
two simulations in rain-free conditions with strong heterogeneity in soil moisture were
always close to identical, a result which is independent of whether default or site-specific
vegetation and soil parameters are used. Because the spatial variability in soil moisture
throughout the catchment has the same order of magnitude as the amount of rain falling in
a typical convective storm (commonly 10% of the vegetation's root zone saturation), in a
semi-arid environment, any non-linearity in the relationship between transpiration and the
soil moisture available to the vegetation has limited influence on area-average surface fluxes.
33
Taylor, Christopher. "The influence of mesoscale surface variability on the atmosphere." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318578.
Full text
34
Andrew, Jennifer Alice MaireÌad. "Tropical Atlantic sea surface height and heat storage variability." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415660.
Full text
35
Berry, David Inglis. "Surface forcing of the North Atlantic : accuracy and variability." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/145001/.
Full textAbstract:
A new methodology to estimate the turbulent air – sea heat and moisture fluxes and their uncertainty is developed and assessed using Voluntary Observing Ship (VOS) observations. Whilst important drivers of the global oceanic and atmospheric circulation these fluxes remain poorly quantified, both in terms of mean value and uncertainty. The new methodology addresses both of these issues and is extensible to other data sources. The individual observations are first bias and height adjusted to remove systematic errors and the impact of changing observing heights. They are then characterised in terms of random errors using a semi-variogram analysis and a range of variogram models. The data quality and sampling are then taken into account using optimal interpolation (OI) to grid the observations, producing daily mean fields and uncertainty estimates. These are then used to estimate the fluxes and flux uncertainty on both daily and monthly time scales. Comparisons of the mean fields and fluxes to the original input data and to independent buoy observations show the fields not to be significantly biased. The adjustments applied before gridding and flux calculation are also shown to improve the agreement with the buoy observations. The uncertainty estimates are assessed using a series of cross validation experiments and 3-way error analyses to make alternative estimates of the uncertainty. These alternative estimates are shown to be of the same order of magnitude as the OI uncertainty estimates and generally to be within 10 – 20% of the OI estimate. Whilst all three estimates are similar there are some systematic differences. The OI uncertainty estimates tend to be lower (higher) than the alternative estimates in high (low) variability regions. The representation of the variability in the new dataset is examined and shown to be improved compared to previous VOS based datasets. The adjustments are shown to have little impact on the temporal trends in temperature and humidity whilst reducing the wind speed and sensible and latent heat flux trends. These reduced trends are thought to be more realistic. The wind speed trend after adjustment is more similar to the trends reported in previous studies using reanalysis model output. However, there are still some differences in the trends, with the VOS based estimates larger, leading to uncertainty in trend estimates. The trends in the adjusted latent and sensible heat flux estimates are similar to those seen in other flux datasets but when compared to changes in the upper ocean heat content may still be too large. This may be due to the overestimate of the wind speed trend. Overall the uncertainty in the wind speed trend gives the largest uncertainty in the flux trends. Finally, the advances made in developing the new methodology are summarised and the potential uses of the new dataset identified. Future work and improvements are then suggested.
36
Kowalski, P. C. "Models of interannual mid-latitude sea surface temperature variability." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1394920/.
Full textAbstract:
Well established and novel simple mixed layer models are used to investigate some of the factors influencing mid-latitude sea surface temperature variability. This thesis focuses in particular on the re-emergence mechanism and the factors that influence it. The re-emergence mechanism describes the process whereby winter sea surface temperature anomalies can become sequestered below the mixed layer as it reforms in the spring/summer and are entrained into the mixed layer in the following winter, subsequently impacting the sea surface temperature. In chapter 2 the idealized mixed layer column model used in Stevenson [36] and the quasi-geostrophic wind driven ocean model are derived. Chapter 3 investigates how sea surface temperature anomalies are generated and decay through mixed layer processes and in the absence of atmospheric feedback. The e ect of atmospheric feedback on the sea surface temperature and mixed layer is investigated in chapter 4. Two new models of the re-emergence mechanism are presented in chapter 5: the first is a stochastic two season model and the second is an entraining mixed layer model with a fixed mixed layer annual cycle. These models are used to investigate some of the factors, such as the diff erence between the summer and winter mixed layer depth, that influence the re-emergence mechanism. The impact of interannual mixed layer depth variability on the re-emergence mechanism is then investigated using the model of Stevenson [36]. In chapters 6 and 7, the impact of local Ekman pumping and associated Rossby wave induced vertical motion on the sea surface temperature, the mixed layer and the re-emergence mechanism are investigated.
37
Washington, Richard. "Interannual and interdecadal variability of African rainfall." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396138.
Full text
38
Joyce, Andrew Noel. "Modelling surface climate over complex terrain for landscape ecology." Thesis, Durham University, 2000. http://etheses.dur.ac.uk/4245/.
Full textAbstract:
Climate exerts a fundamental control on ecosystem function, species diversity and distribution. Topographic variability may influence surface climate, through processes operating at a landscape- scale. To quantify and model such influences, the topography of a 72 km(^2) area of complex terrain, (including the Moor House National Nature Reserve in northern England) was analysed at 50 m resolution. A suite of topographic variables was created, including distance relative to the Pennine ridge (dist), and elevation difference between each grid cell and the lowest grid cell within a specified neighbourhood {drain). Automatic weather stations (AWS) were deployed in a series of networks to test hypothetical relationships between landscape and climate. Daily maximum air temperature, daily mean soil temperature and daily potential evapotranspiration can be modelled spatially using a daily lapse rate calculated from the difference between daily observations made at two base stations. On days with a south easterly wind direction, daily mean temperature is estimated as a function of lapse rate and dist; the spatial behaviour of temperature is consistent with a föhn mechanism. Daily minimum temperature is modelled using lapse rate and drain on days with a lapse rate of minimum temperature shallower than -2.03 x 10 C m(^-1), incorporating the effects of katabatic air flow. Daily solar radiation surfaces are estimated by a GIS routine that models interactions between slope and solar geometry and accounts for daily variations in cloudiness and daylight duration. The daily climate surfaces were tested using data measured at a range of AWS locations during different times of year. The accuracy of the daily surfaces is not seasonally-dependent. The spatial climate data are particularly well suited to landscape-scale ecology because the methods account for prevailing topoclimatic constraints and because separate climate surfaces are generated for each day, capturing the high frequency variability characteristic of upland regions.
39
Bhatt, Rajesh. "Investigating the Variability of Water and Soil Salinity using Watershed Model and Remote Sensing Techniques: A Case Study of Mentor Marsh, Ohio." Youngstown State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1596549383903397.
Full text
40
Svensson, Jonas. "Horizontal Meter Scale Variability of Elemental Carbon in Surface Snow." Thesis, Stockholms universitet, Institutionen för naturgeografi och kvartärgeologi (INK), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-59712.
Full textAbstract:
Soot deposited in snow and ice lowers the albedo of the surface and affects the radiative balance. Soot’s climatic forcing has received increased attention during the last decade, however, measurements of soot concentrations in Arctic snow are rare. This thesis investigates the horizontal variability of elemental carbon (EC), a proxy of soot, on a meter scale in surface snow from a site with limited regional pollution in Arctic Finland and a site with significant regional pollution near Stockholm, Sweden. A variability of EC in the sampled grid-nets was observed at both of the sites; however, the site with less pollution affecting it presented greater variation in comparison to the polluted site. In side-by-side ratios between neighboring samples, a ratio of as much as ~16 is observed, presenting the potential variation at the less polluted site. An important process that is partly responsible for the variation at this site is wind. The EC concentrations increased over time at both of the sites, which supports the hypothesis that EC remains at the snow surface even as snow melt occurs in the spring.
41
Jones, Steve. "Spatio-temporal variability in surface ocean pCO₂ inferred from observations." Thesis, University of East Anglia, 2012. https://ueaeprints.uea.ac.uk/42328/.
Full textAbstract:
The variability of surface ocean pCO₂ is examined on multiple spatial and temporal scales. Temporal autocorrelation analysis is used to examine pCO₂ variability over multiple years. Spatial autocorrelation analysis describes pCO₂ variability over multiple spatial scales. Spatial autocorrelation lengths range between <50 km in coastal regions and other areas of physical turbulence up to 3,000 km along major currents. Analysis of the drivers of pCO₂ shows that ocean currents are the primary driver of spatial variability. Autocorrelation lengths of air-sea CO2 fluxes are approximately half as long as for pCO₂ due to the effects of highly variable wind speeds. The influence of modes of climate variability on ocean pCO₂ and related air-sea CO₂ fluxes is examined through correlations of climate indices with interannual pCO₂ anomalies separated from the long-term trend and mean seasonal cycle. Changes in the El Niño Southern Oscillation alter pCO₂ levels by -6.6 ± 1.0 μatm per index unit (μatm iu⁻¹) in the Equatorial Pacific, leading to changes in air-sea flux of up to 0.40 ± 0.06 Pg C yr⁻¹. The Pacific Decadal Oscillation shows statistically significant correlations with pCO₂ across the Equatorial Pacific, North Pacific and North Atlantic. No statistically significant correlations are found with the North Atlantic Oscillation in the North Atlantic. An important product of the analysis performed in this thesis is a spatially and temporally complete interpolated data set of surface ocean pCO₂ data over an extended period. This data product is the first of its kind, both in terms of its coverage and the fact that it does not rely on the derivation of empirical relationships between pCO₂ and other biogeochemical variables. The technique works as well as or better than previous regional interpolations, with 90% of values likely to be within 30μatm of the actual pCO₂ value.
42
Goodall, Robert Harry. "3D tooth surface texture analysis : methodological variability and marine mammals." Thesis, University of Leicester, 2017. http://hdl.handle.net/2381/39953.
Full textAbstract:
Tooth microwear occurs when an animal processes food, producing microscopic pits and scratches on tooth surfaces, providing evidence of tooth movements and food properties. 3D microwear analysis is a growing field of study, where sub-micron scale tooth surface textures are used to compare populations with dietary differences. It has been primarily employed to study terrestrial vertebrates, however, the technique has rarely been applied to aquatic vertebrates, and never to aquatic mammals. Furthermore, the technique suffers from methodological variability. To address these points this thesis presents the results of five studies using 3D microwear analysis, three of which investigate different aspects of methodological variability, and two investigate the utility of 3D microwear analysis to differentiate diet in marine mammals, both across multiple species, and within a single species. An investigation of seven commonly used moulding compounds of varying viscosity demonstrated that mid-viscosity President Jet Regular Body produced the most accurate and precise moulds of tooth surface texture. An investigation was also carried out to test the effect of scale limiting 3D surfaces using 40 different combinations of operator (Nth order of polynomial) and filter to produce roughness surfaces. It was shown that high variability exists between resulting surfaces depending on the operator and the filter used. A combination of 6th order of polynomial, robust Gaussian filter and 0.025mm nesting index produced the greatest separation of known dietary groups while also being comparable to surfaces generated using many other combinations. An investigation into the effect of using four different microscopes to collect 3D tooth surface texture data showed high variability between resulting roughness parameter values and sensitivity to dietary differences depending on the microscope used. When testing the ability of 3D microwear analysis to separate ten marine mammal species into four known dietary groups, it was shown that this technique is highly sensitive to dietary differences, and provides information about the dietary evolution of extinct cetaceans. Finally, when using dentin tooth surfaces to test the ability of 3D microwear to detect differences between Orcinus orca dietary populations, it was found that their surface texture appears highly variable, and that little separation was possible between dietary groups.
43
Wagstaffe, Daniel Raymond. "Spatial Variability of Soil Velocity using Passive Surface Wave Testing." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1526.
Full textAbstract:
Lifelines such as highways, pipelines, telecommunication lines, and powerlines provide communities with vital services, and their functionality is dependent upon the foundation soil that supports them. However, when designing the infrastructure, it can be difficult to know where to test the soil in order to give spatially representative sampling, particularly for long, lifeline structures. Finding this distance requires knowledge of the spatial correlation and/or the spatial variability of the soil parameter (stiffness, cohesion, etc.). But this correlation distance is not typically found in practice because it requires large amounts of data and the costs of retrieving that data can be high. Lack of representative sampling can lead to an overly conservative design and too much sampling can create an overly expensive sampling program. In this study, multiple tests using the geophysical method of spatial autocorrelation (SPAC) were conducted to find the soil stiffness along a 310 meter long profile. SPAC records passive surface waves which sample the underlying soil, and these surface waves can be used to create a shear wave velocity profile of the site. The spatial continuity of the stiffness (the soil velocity values) was then found using geostatistics. The geostastical tool primarily used in this study was the (semi-)variogram, but the covariance function and the correlogram are also shown. By using these tools, the spatial correlation/variability can give an estimate of the how far apart to test the foundation soil so that the data is spatially representative. In other words, finding the distance that the soil parameter is minimally correlated with itself. This study found the distance (the range of the semi-variogram) to be 70 meters for 5 meters depth, 100 meters for 10 to 15 meters depth, and 90 meters for 30 meters depth.
44
Yang, Lei. "Greenland ice sheet change surface climate variability and glacier dynamics /." The Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=osu1180121203.
Full text
45
Peyser, Cheryl E., Jianjun Yin, Felix W. Landerer, and Julia E. Cole. "Pacific sea level rise patterns and global surface temperature variability." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/621707.
Full textAbstract:
During 1998-2012, climate change and sea level rise (SLR) exhibit two notable features: a slowdown of global surface warming (hiatus) and a rapid SLR in the tropical western Pacific. To quantify their relationship, we analyze the long-term control simulations of 38 climate models. We find a significant and robust correlation between the east-west contrast of dynamic sea level (DSL) in the Pacific and global mean surface temperature (GST) variability on both interannual and decadal time scales. Based on linear regression of the multimodel ensemble mean, the anomalously fast SLR in the western tropical Pacific observed during 1998-2012 indicates suppression of a potential global surface warming of 0.16 degrees 0.06 degrees C. In contrast, the Pacific contributed 0.29 degrees 0.10 degrees C to the significant interannual GST increase in 1997/1998. The Pacific DSL anomalies observed in 2015 suggest that the strong El Nino in 2015/2016 could lead to a 0.21 degrees 0.07 degrees C GST jump.
46
Davies, Sarah B. "Vegetation Dynamics of a Tidal Freshwater Marsh: Long-Term and Inter-Annual Variability and their Relationship to Salinity." W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1539617817.
Full text
47
Widmer, Chad L. "Influences of temperature and salinity on asexual reproduction and development of scyphozoan jellyfish from the British Isles." Thesis, University of St Andrews, 2015. http://hdl.handle.net/10023/6326.
Full textAbstract:
Jellyfish (Phylum Cnidaria, Class Scyphozoa) play important roles in pelagic ecosystems as predators and prey. Seasonally they form blooms facilitating reproductive success, but that are at times problematic for human enterprise. Medusa abundance has been correlated with environmental variables in several instances. However, the direct mechanisms for changes in medusa abundance are unclear. As global sea surface temperatures continue to change there is increasing concern that warming may enhance conditions favourable for the generation of jellyfish medusae. It is important to understand the ways in which temperature affects all life history stages of jellyfish if we are to begin to understand factors associated with jellyfish bloom formations, but how temperature and salinity affects life history stages of scyphozoan jellyfish from British waters remains largely unknown. In Chapter 1 I provide a general introduction to some key issues important to the formation of jellyfish blooms. In Chapter 2 I present results for experiments testing the effects of temperature on settlement and metamorphosis of planulae larvae of Cyanea capillata, Cyanea lamarckii, Chyrsaora hysoscella, and Aurelia aurita. Chapter 3 reports on the effects of temperature and salinity on survival, and asexual reproduction of scyphistomae of the same species. Chapter 4 reports on the effects of temperature and salinity on growth of newly released ephyrae of each of the above mentioned species, as well as the effects of starvation on survivorship on ephyrae of A. aurita originating from two distinct populations of scyphistomae. In Chapter 5 I provide a brief summary of significant findings for each life history stage, their theoretical implications when taken together, and next steps for future research. I also offer recommendations for ecosystem managers with an eye toward affecting the numbers of near-shore jellyfish medusae generated each season in the waters surrounding the British Isles.
48
Li, Wei 1982. "The variability of North American winter surface temperature and its relation to the sea surface temperature /." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101604.
Full textAbstract:
The first two empirical orthogonal functions of the winter (DJF) surface air temperature (SAT) over North America are associated with the North Atlantic Oscillation (NAO) and the Pacific/North American (PNA) pattern in the NCEP reanalysis. Lagged correlations between the North American SAT structures and the sea surface temperature (SST) were computed. There is a small lag between the tri-pole SST anomaly pattern of the North Atlantic Ocean and the first SAT mode. The second SAT mode lags the eastern Tropical Pacific SST anomaly by two months, associated with ENSO through the winter. A similar analysis is conducted on the seasonal forecasts to see if the forecast models capture the above links. GCM3 captures the ENSO forcing and has the PNA response. GEM captures the link between the SAT and the tripole SST anomaly pattern in North Atlantic. Although GEM captures the ENSO signal, it cannot form the PNA to further this tropical forcing into North America.
49
Goodkin, Nathalie Fairbank. "Geochemistry of slow-growing corals : reconstructing sea surface temperature, salinity and the North Atlantic Oscillation." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40969.
Full textAbstract:
Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007.Includes bibliographical references.
A 225-year old coral from the south shore of Bermuda (64°W, 320N) provides a record of decadal-to-centennial scale climate variability. The coral was collected live, and sub-annual density bands seen in x-radiographs delineate cold and warm seasons allowing for precise dating. Coral skeletons incorporate strontium (Sr) and calcium (Ca) in relative proportions inversely to the sea surface temperature (SST) in which the skeleton is secreted. [Delta]180 of the coral skeleton changes based on both temperature and the [delta]180 of sea water ([delta]Ow), and 6Ow is proportional to sea surface salinity (SSS). Understanding long-term climate variability requires the reconstruction of key climate parameters, such as sea surface temperature (SST) and salinity, in records extending beyond the relatively short instrumental period. The high accretion rates, longevity, and skeletal growth bands found in coral skeletons make them an ideal resource for well-dated, seasonal climate reconstructions. Growing between 2 and 6 mm/year and reaching more than im in length, slow-growing corals provide multi-century records from one colony. Additionally, unlike the fast growing (10-20 mm/year) species Porites, slow-growing species are generally found in both tropical and sub-tropical locations greatly expanding the geographical location of these records. A high resolution record (HRR, ~11 samples per year) was drilled for the entire length of the coral record (218 years). Samples were split and Sr/Ca, [delta]180, and [delta]13C were measured for each sample. Sr/Ca was used to reconstruct winter time and mean-annual SST. Oxygen isotopic measurements were used to determine directional salinity changes, in conjunction with Sr/Ca based SST reconstructions.
(cont.) Winter-time and mean annual SSTs show SSTs -1.5 'C colder during the end of the Little Ice Age (LIA) relative to today. Simultaneously, SSS is fresher during that time. Sr/Ca based climate reconstructions from coral skeletons have been met with some skepticism because some reconstructions show temperature changes back in time that are 2-4 times greater than the reconstructions of other marine proxies. In this study, we show that when using bulk-sampled, slow-growing corals, two steps are critical to producing accurate reconstructions: 1) incorporating growth rate into multi-variant regressions with SST and Sr/Ca and 2) using multiple colonies that grew at the same time with varying average growth rates and Sr/Ca. Application of these novel methods over the period of the instrumental record from Hydrostation S (monthly since 1954, 32°10'N, 64°30'W) reduces the root mean square of the residuals between the reconstructed SST and the instrumental SST by as much as 1.52'C to 0.460C for three coral colonies. Winter-time SSTs at Bermuda are correlated to phases of the North Atlantic Oscillation (NAO), a meridional oscillation in atmospheric mass. Much uncertainty remains about the relationship between the NAO and the ocean, and one critical outstanding question is whether anthropogenic changes are perturbing the system. Using winter Sr/Ca as a proxy for temperature, we show strong coherence to the NAO at multi-decadal and inter-annual frequencies. These coral records show significant changes in variance in the NAO during the late 20th century compared to the cooler LIA, but limited changes in the mean phase (positive or negative) of the NAO, implying that climate change may be pushing the NAO to extremes but not to a new mean position.
by Nathalie Fairbank Goodkin.
Ph.D.
50
Shi, Qiang [Verfasser]. "Seasonal Variability of Iodomethane Production in the Surface Ocean / Qiang Shi." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1031421289/34.
Full text