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Continental rifts are commonly flanked by zones of high elevation. Proposed uplift mechanisms include active and induced asthenospheric upwelling, and isostatically driven lithospheric flexure. Although these hypotheses make testable and distinct predictions of the relative timing of crustal extension and rift flank uplift, the difficulty of closely constraining these processes in modern or ancient rift zones means that the issue remains controversial. This study focuses on the Loreto rift segment of the Baja California peninsula, which forms the western margin of the Late Neogene Gulf of California rift. The Loreto region is characterised by a prominent east-facing rift escarpment which separates a low-elevation coastal plain, which hosts rift-bounding faults, from a west-tilted, topographically asymmetric rift flank, incised by west-draining canyons. On the coastal plain, slip on the rift-bounding Loreto fault has driven westward retreat of the escarpment. Footwall exhumation due to escarpment retreat is reconstructed using the apatite fission track and apatite (U-Th)/He low-temperature thermochronometers to constrain the minimum age of escarpment retreat and thus also Loreto fault slip. On the rift flank west of the escarpment, canyon incision depths are obtained by analysis of digital elevation models and used as a proxy for minimum uplift magnitude. The timing and rate of rift flank canyon incision, a proxy for the timing and magnitude of rift flank surface uplift, is constrained using 40Ar/39Ar dating of lavas which display cut and fill relations with the rift flank canyons. These lavas also provide a resistant cap atop canyon interfluve mesas, and the extent of this resistant cap likely controls the extent of rift flank catchment denudation in response to uplift. The principal finding of this thesis is that rift flank surface uplift was coeval with crustal extension at Loreto, consistent with predictions made by models of rift flank uplift driven by the flexurally-distributed isostatic response to the lithospheric unloading associated with crustal extension.

The viability of using a foraminifera-based transfer function method to reconstruct the local relative sea-level for the Mersey Estuary was assessed in this study, which has not been previously investigated in the UK in the context of application in a strongly macrotidal setting. A total of 105 surface samples were collected across two saltmarshes. Foraminiferal analysis was carried out, along with several environmental variables (organic matter content, salinity, pH, and grain size) to establish the species distribution of foraminifera and their relationship with elevation. Two main zonations were found: a high-to-middle marsh zone occupied by Haplophragmoides spp., J. macrescens and M. fusca; and a low marsh zone composed of increasing numbers of calcareous species including Elphidium spp.; and Haynesina spp. Foraminiferal distributions along each transect were found to be controlled predominantly by elevation and distance from tidal influence, whilst combined datasets reflected intra- and inter-site variability in the assemblages. Elevation was still found to have an important control over the distributions, with a strong relationship between the species zonations and elevation (r2 = 0.8). Therefore, the dataset (82 samples) formed a local training set in which a transfer function for the relationship between foraminifera species and elevation was developed. WAPLS was used as it produced the highest predictive ability (r2 jack = 0.85) and lowest prediction errors (RMSEPjack = 0.11 m). Regional and combined (local plus regional) transfer functions were also developed but the local transfer function produced the most accurate and reliable reconstruction. Reconstructions were carried out for both saltmarshes with reference to a sediment chronology which was established using radionuclides and pollution indicators. The reconstructions demonstrated the vast difference in the saltmarsh development and record of sea level between the sites. Oglet Bay developed as a result of increased accommodation space arising from changing estuary morphology, resulting in rapid accretion (2.34 cm year-1) and was found to be strongly influenced by tidal channel migration. Decoy Marsh accreted at a slower pace (0.32 cm year-1) and was less affected by tidal or morphological changes. Both reconstructions were affected by decalcification resulting in the reconstructions dating back to 1978 at the most. The reconstructed rates of sea-level change were 1.8 cm year-1 for Oglet Bay and 1.1 cm year-1 for Decoy Marsh, both of which over-estimate the trend from the monthly instrumental record (1.04 cm year-1) over the same period. The study highlights the problems which may arise when conducting research in an inner estuary which is strongly macrotidal, including tidal range changes, tidal asymmetry, and decalcification, but also demonstrates that a relatively precise and reliable reconstruction is achievable.

Internal gravity waves in the oceans are a limited scale process capable of providing sufficient energy to activate strong diapycnal mixing near sloping bathymetry. This can account for a significant portion of oceanic vertical mixing. Mixing can be locally intense, transporting colder nutrient-rich bottom water up onto continental margins with implications for coastal marine ecosystems and the carbon cycle. Modelling internal waves is particularly challenging. The strong vertical accelerations present in the overturning and breaking of internal waves necessitates a non-hydrostatic model, and the small-scale processes that result from the interaction of internal waves with bathymetry mean that traditional structured mesh models require high-resolution to adequately capture flow complexity. I present two-dimensional results of numerical simulations of internal waves being generated and interacting with idealised bathymetry, using the Imperial College Ocean Model (Fluidity-ICOM), a non-hydrostatic, finite-element, unstructured mesh model incorporating anisotropic mesh adaptivity. The unstructured nature of Fluidity-ICOM allows the mesh to be optimised to represent complex bathymetries, as well as capturing the vertically inhomogeneous structure of internal waves. Convergence of the model to analytical results has been demonstrated by modelling internal wave propagation in a linearly stratified fluid. Adaptive mesh simulations have been found to adequately capture the dynamics of internal wave breaking at a slope, and the degeneration of interfacial waves into solitary internal waves, with less computational resources than traditional models. However, further work is needed to simulate the internal leewave generation mechanism of flow over topography.

The Early Eocene (47-56 Ma) 'greenhouse' climate represented the warmest climatic conditions witnessed in the last 90 million years, with peak Eocene warmth (the Early Eocene Climatic optimum, EECO) occurring around 50-52 Ma (Sexton et al. 2006; Bijl et al. 2009; Zachos et al. 2008; Littler et al. 2014) with subsequent global cooling thereafter (Sexton et al. 2006; Zachos et al. 2008). Ocean circulation plays a critical role in redistributing thermal energy across the planet and providing ventilation to the deepest parts of the ocean. Understanding how it may have operated in a globally warm world with little equator-to-pole gradients is paramount to understanding how it may respond to increasing temperatures today. The prevailing view of the early Eocene ocean was that deep-water formation was confined to the Southern Ocean, with little or no deep-water formation in the North Atlantic, unlike today. This study explores whether there is evidence for deep-water formation in the high latitude North Atlantic during the extreme climatic warmth of the early Eocene and its stability across transient climatic excursions. It also explores the strength and vigour of ocean circulation and whether this was influenced by the global decline in temperature following early Eocene peak-warmth. It utilises the neodymium isotopic signature of fossilised fish teeth (εNd) that is widely utilised to trace the movements of deep-water masses and can be used to reconstruct paleooceanic circulation along with detrital εNd that is an indicator of sediment provenance. It combines these with fish tooth rare earth element concentrations and sediment core XRF. Four key locations are utilised. Two on the Newfoundland margin in the West North Atlantic, and one from the high North Atlantic in the Labrador Sea, both idea1 locations to identify the potential outputs of North Atlantic deep-water formation. The fourth site is Demerara Rise in the Equatorial Atlantic, chosen to monitor changes in the dominant source of deep-water sources from the North or the South.

The nonlinear hyperbolic partial differential equations applicable to long wave propagation in two spatial dimensions are derived, under the assumptions of hydrostatic pressure distribution and quadratic bed friction. The relevance of linearised versions of these equations to various tidal configurations is discussed. Linearisation, and the assumption of harmonic wave motion, reduces the hyperbolic system to elliptic form, so that steady-state solutions become available. Conventional harmonic methods are unsatisfactory in shallow estuaries, where the unsteady tidal conditions must be computed by an initial value method. The potential existence of discontinuities in the solution domain of the hyperbolic long wave equations is demonstrated, and the associated characteristic surfaces, which separate disturbed and undisturbed regions within this domain, are delineated. An explicit numerical technique, based on finite difference approximations to the differential relationships which hold on these characteristic surfaces, is proposed. The modifications necessary at the estuary boundaries are described. The stability and consistency criteria associated with the proposed method are established. Violation of the consistency conditions causes a computer program based on estuary schematisation by an orthogonal curvilinear grid to fail in a complex bidirectional situation. However, comparisons with the harmonic solutions in various unidirectional test cases show good agreement, and shallow-water effects appear to be correctly reproduced. A program based on a rectangular network is found to satisfy the consistency conditions. The computational efficiency achieved is comparable to that available with direct finite difference techniques. Finally, the inclusion in the proposed numerical scheme of additional estuarial parameters is discussed.

Cold-water corals are a relatively new archive of past ocean conditions. They are found in areas that sedimentary records struggle to record, and their aragonite skeletons can be dated using precise uranium-series techniques. Arguably, the most successful use of cold-water corals in palaeoceanography has been using radiocarbon to trace water mass ages and mixing. For example, these techniques have revealed discrete periods of Southern Ocean deglacial ventilation, a likely driver of the deglacial rise in atmospheric C02. However, the use of cold-water corals in palaeoceanography is hampered by slow dating procedures and a scarcity of palaeocean proxies that are free of biological mediation (vital effects). My work aims to address these issues and improve the utility of the cold-water coral palaeocean archive.

Ocean acidification and climate change are occurring as a result of anthropogenic release of carbon dioxide (C02) into the atmosphere. Changes in climate and ocean chemistry are occurring concomitantly and at a faster rate than previously recorded in Earth's history, yet little is understood about how they will influence the population dynamics and ecology of many marine organisms. The barnacle Semibalanus balanoides is a major space occupier on rocky shores in northern Europe and hence changes in its population ecology can have a broad influence on other species. An intertidal high CO2 microcosm system was developed in order to determine how temperature and CO2 interact to affect S. balanoides egg development, nauplii development and cyprid development. Changes in abundance and viability of the early life stages impacts the supply of larvae arriving in the intertidal and post settlement mortality determines the number of individuals reaching reproductive age. Laboratory experiments indicated that elevating CO2 and temperature slows the metamorphosis of cyprids thereby increasing their exposure to desiccation. Increased temperature and CO2 had greatest impact on smaller individuals prior to metamorphosis with poor survival being linked to slow growth and ability to calcify. Embryo development rates were also reduced significantly by elevated CO2, while the survival of brooding adults was lowered. These experimental data were then incorporated into a population model used to predict the changes in population abundances over the coming century. At the southern edge of its geographic range, S. balanoides is predicted to be most significantly impacted by temperature, although in colder years CO2 has a significant influence. A conceptual model developed using these empirical data suggests that at the northern edge of its geographic range, S. balanoides, appears more likely to be impacted by ocean acidification than temperature, particularly through changes in resource allocation and changes in life history.

Dissolved organic carbon (DOC) is the quantitatively most important organic carbon reservoir in the world's oceans and its determination at ocean margins, where the exchange of terrestrial and oceanic organic matter occurs, is important for estimating cross-slope fluxes to deep waters. With the increased accuracy and precision (-1%) of analytical methodologies, small changes in the DOC pool can be detected (i.e. 1- 2uM-C). This study investigated the biogeochemical cycling of DOC at the Iberian Margin upwelling system (42-43°N, --9-10°W), where contrasting seasonal hydrologic phenomena occur (e.g. summer upwelling, winter poleward current). Spatial and temporal DOC distributions were determined using high temperature catalytic oxidation (HTCO) techniques. DOC concentrations generally decreased with distance from the continental shelf and with increasing depth, although localised accumulation was observed in surface as well as in deep waters with a mean excess of up to 16 uM-C over background concentrations (57 uM-C). DOC concentrations in surface waters were closely associated with bacterial productivity and dissolved organic nitrogen (DON) production was facilitated by photosynthetic extra-cellular release from phytoplankton. There was no marked difference in DOC concentrations between the summer and winter seasons due to increased mineralization during the summer and lateral inputs during the winter. DOC production exceeded removal rates in summer upwelled surface waters following enhanced biological activity, in the winter surface poleward current and in deep waters that contained high levels of suspended particulates. DOC from terrestrial run-off was recycled rapidly at the coast before it could be exported to the shelf Cross-slope export of accumulated DOC was generally hindered by the net onshore velocity component during both winter and summer seasons and by the presence of water masses travelling along-slope.

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