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The TOPEX/Poseidon altimetry mission was developed as a NASA/CNES collaboration to provide accurate sea surface height (SSH) measurements. The TOPEX mission's altimeter is the first, and so far only, dual frequency system in space. The use of two frequencies allows a correction to be made for the radar pulse delay imposed by the Earth's ionosphere which would otherwise lead to an underestimation of SSH. Not only does TOPEX/Poseidon provide the most accurate SSH measurements yet from space, it also provides the first ever quasi-global measure of the integrated electron content (IEC) of the ionosphere. This thesis utilises TOPEX/Poseidon data in a combined study of both the oceans and the ionosphere. Firstly a study of the dependence of the IEC on geomagnetic disturbances, and the spatial coherence scale of the IEC is performed by comparison with the International Reference Ionosphere, an empirical ionospheric model. A systematic dependence of IEC with geomagnetic disturbance is found, and the first ever quasi-global maps of IEC spatial coherence distance are produced. This investigation may lead to an improvement in the accuracy of the model, and hence also that of single frequency altimeter systems, which must rely on such empirical models for their correction to the ionospheric delay. Secondly the tropical Pacific Ocean is studied, in particular the characteristics of large scale wave activity in relation to the devastating climatic/oceanic phenomena known as El Nino. Kelvin, Rossby and tropical instability waves are identified, and their interactions and possible mechanisms related to El Nino are investigated. Evidence for both western and eastern boundary reflections are presented, and their significance to the delayed oscillator mechanism is discussed. The study illustrates the necessity for highly accurate SSH measurements.

The mid-Neoproterozoic to mid-Cambrian Dalradian Supergroup metasedimentary rocks of Scotland and Ireland contain vein-hosted gold mineralisation, including the Cononish deposit, Tyndrum, with a resource of 163,200 oz Au. Through identifying new mineralised occurrences and understanding the genesis of these and the Cononish deposit, the characteristic features of the hydrothermal system are identified. This study aims to improve exploration strategy by defining a specific genetic model. Newly identified veins, in the Tyndrum area, are classified into three types: early molybdenite-bordered fractures, later gold-bearing poly-metallic veins and quartz-only veins. High-grade (>10 ppm) gold mineralisation at the Cononish deposit has distinct high Te (104 ppm) and Ag (119 ppm) with low Au/Ag (0.25). Other gold-bearing poly-metallic veins exhibit lower Te (8 ppm), higher As (234 ppm) and Au/Ag (1.3) at high grade (>10 ppm Au). Gold occurs with sulphides and δ34S data (average +6.7±2.8 ‰) indicate a significant portion of the sulphur is sourced from the metasedimentary succession (≥32-100%) with a small, but genetically significant, magmatic-sourced component (≤68%). The source of sedimentary sulphur is not the immediate host rock and is inferred to be stratigraphically overlying, but structurally underlying, Easdale Subgroup lithologies. 40Ar/39Ar, Re-Os and U-Pb geochronology on muscovite, K-feldspar, molybdenite and rutile from veins and altered wall rock records two metallogenic events; metamorphic molybdenite at 477-439 Ma and post-metamorphic gold at 408-407 Ma. All gold-bearing veins are coeval with the gold-bearing Rhynie Chert (c. 407 Ma), suggesting a regional system of hydrothermal fluid flow. This is coincident with the last stage of emplacement of the post-orogenic granite suite (c. 430-408 Ma) and fault movement on the Great Glen and subsidiary faults (c. 430-390 Ma) interpreted to be as a result of the change of the stress field to sinistral transtension (c. 420-400 Ma).

Reactive transport is an important field of study in the earth sciences. It captures both natural phenomena, and industrial and environmental applications, including transport of pollutants in the subsurface, nuclear waste storage, and carbon storage. The aim of this thesis is to provide a better understanding of coupled physico-chemical processes governing these phenomena as well as to be used as tools for better understanding these environmental applications. We introduce from first principles a novel pore-scale modelling approach capable of simulating single-phase fluid-fluid reactive transport directly on voxels of 3D images of porous media constructed from X-ray tomography. We use a streamline-based particle tracking method for simulating flow and transport, while for reaction to occur, both reactants must be within a diffusive distance. We assign a probability of reaction, as a function of the reaction rate constant and the diffusion length. The model for reaction is validated against analytical solutions in a free fluid as well as against experimental data on reactive transport in porous media. It takes into account the degree of incomplete mixing present at the sub-pore level. We demonstrate the nature of dynamic changes in the reaction rate, which is related to the degree of pore-scale mixing. Our model does not use any calibrating parameters to fit empirical data unlike other models published in the literature. The model is then extended to investigate the impact of pore structure heterogeneity, transport, and reaction conditions on the overall reaction rate in porous media by studying different classes of porous media. The overall reaction rate varies significantly according to the degree of heterogeneity and transport conditions. It is found that the rate of reaction is a subtle combination of the amount of mixing and spreading that cannot be predicted from the dispersion coefficient alone. At low Péclet number, the effective reaction rate is principally controlled by the amount of mixing due to diffusion. On the other hand, at high Péclet number the reaction rate is controlled by a combination of pore-scale mixing due to spreading and the degree of heterogeneity of the pore structure.

The annual migration of the North Pacific Subtropical High, fuelled by tropical heat and moisture---derived partly from the Atlantic---drives seasonal coastal upwelling and, importantly, transports heat into the mid-latitudes. Interannual to orbital cyclicity affects eastern North Pacific climate by varying the relative strengths/interactions of the Subtropical High and the Aleutian Subpolar Low. In modern Guaymas Basin---situated at the wet/dry subtropical divide---dry-season diatom productivity alternates with wet-season terrestrial flux, and pre-formed low-oxygen intermediate waters ensure varve deposition. High-resolution logging of 75% laminated, 63 m, continuous piston core MD02-2515 and companion 6 m kasten core MD02-2517 has identified eight sediment fabric types, six of which are laminated with systematic variations in relative lamina thickness and presence/absence of sub-laminae. Based on observed climate and supported by climate proxies provided by continuous X-ray fluorescence, colour, magnetic susceptibility, sediment density, biogenic silica, carbon and microfossil analyses, the sediment fabric types have been interpreted as the result of climatic/oceanographic conditions produced by variations in the strength of the North Pacific Subtropical High and the extent of its migration. Varve thickness, 6180 stratigraphy and correlation with the o13C stratigraphy of nearby radiocarbon dated core JPC-56 (Keigwin, 2002) gives an age range of 0-36,000 Years. Systematic variations in the predominance of one or more sediment types reveal precessional forcing, which drives a 5000-year oscillation of millennial- and centennial-scale wet/dry cycles, the former are associated with June/December perihelion, the latter with March/September perihelion. Between 34-11,000 yr BP there are significant non-laminated intervals every 5000 years. This study indicates that the Trade Winds are confined close to the equator during the glacial. This breaks the hydrological link between the Atlantic and Pacific and reduces dysoxia in coastal waters.

Understanding how clastic injectites form is important, as they are increasingly being recognised as significant components of sedimentary basin-fills, but are not predicted by standard sedimentary facies models. This study focuses on exhumed examples of injectites from the Karoo Basin, South Africa, and utilises a multidisciplinary approach to investigate clastic injectites across a variety of scales. Small-scale analysis of injectites allows a classification of fracture patterns preserved on sill and dyke margins. These are used to interpret propagation direction through brittle, fine grained sediments under a laminar flow regime at depth in closed fracture networks. In contrast, shallow injectites, where they do not extrude, are identified by; fewer dykes, less stratigraphy crosscut, lower volume of injected material, and in some cases burrows on injectite margins—suggesting exploitation of injectite networks close to the surface. These insights are applied to larger-scale (100s m to km) analysis, where extensive outcrop and well constrained paleogeography permits the injectite geometry to be related to parent sandstone facies and architecture. The influence of fluid flow pre-, syn- and post-injection is investigated across multiple scales. A model for the predictive distribution of injectites is proposed, which highlights the close association of basin-floor stratigraphic traps and sub-seismic clastic injectites. The outcrop data permits construction of forward seismic models demonstrate injectite architecture is scale invariant, which supports the use of outcrop-scale data in seismic-scale interpretations. The integration of outcrop panels, well log data, forward seismic models and subsurface seismic sections has aided the identification of injectites in the subsurface and therefore the ability to discriminate between clastic injectites and parent sandbodies. The increased predictability in the location and character of injectites allows subsurface uncertainty in the impact of clastic injectites on hydrocarbon reservoirs to be reduced.

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