This study uses planktonic foraminiferal assemblages and SST proxy (transfer functions and alkenones) data from the Southern Benguela System, offshore the Cape of Good Hope to examine palaeoceanographic change at this important juncture of the thermohaline circulation. The records of watermass characteristics and variation thus derived are used to understand further climatic mechanisms and feedback within the Southern Hemisphere and globally. Various modes of surface circulation are associated with particular climatic intervals through statistical and ecological analysis of faunal census data. Transitions and early interglacials are associated with watermasses including a significant Indian Ocean component. The main feature of glacials is an eutrophic ocean environment interval (OEI) linked to increased upwelling and filament projection into the Cape Basin. Cooler stadials of interglacials are marked by increased abundance of transitional and oligotrophic species associated with the South Atlantic gyre. These environments are seen in a characteristic order through a typical glacial-interglacial cycle as watermasses respond to insolation changes and thermohaline and atmospheric reorganizations. These are driven by northern hemisphere summer insolation cycles through trade wind strength, ITCZ position, and the position of the Agulhas Retroflection. The South Atlantic gyre signal is determined by austral summer insolation, however. SSTs reconstructions provide a direct record of the changing temperature characteristic of regional watermasses and thus are a second constraint on the interpretations derived from planktonic foraminiferal assemblages. Two techniques are used in this study: faunal-based transfer functions (TFT); and alkenones (U^k’₃₇). Past interglacials were at least as warm as today, and during MIS 5.5 and 11.3 exceeded present values. U^k₃₇ SST records are generally similar to the TFT warm season temperatures, but during peak interglacials (MIS 9.3, 7.3 and 5.5) are an additional ~1.5°C warmer. This difference is ascribed to the sensitivity of the foraminiferal TFT to seasonal changes in upwelling and frontal movements.

Dynamics in the Southern Ocean are dominated by the Antarctic Circumpolar Current (ACC), and this large eastward current has an important influence on the earth's climate. Output from the last six years of the Fine Resolution Antarctic Model, where the mean flow is known, is used to develop techniques for quantifying Rossby waves and eddy activity. Some eastward jets in the mean flow are found to act as waveguides for Rossby waves. Phase speeds are found to increase linearly with frequency, but do not vary with the strength of mean flow. The reason for this is demonstrated using the dispersion relation, but it is shown that Rossby waves cannot be used to measure mean flows in the ACC without a further understanding of the theory involved. A property of the time-average eddy activity, known as the eddy orientation angle, is shown to indicate the axes of the prominent eastward jets in the mean flow. This shows that eddies are acting to force these jets. Five yeas of measurements from the TOPEX/POSEIDON satellite mission are used to identify Rossby waves in the real ocean. Coherent Rossby wave propagation is again confined to localised regions, some of which act as waveguides. Phase speeds are measured in these regions, and shown to be consistent with previous measurements of Rossby waves. An improved resolution dataset, combining TOPEX/POSEIDON and ERS altimetry measurements, is used to analyse the time-average eddy activity and associated forcing on the mean flow in unprecedented detail. Current data from cruises of the World Ocean Circulation Experiment are used in conjunction with altimetry data to estimate the mean flow at locations along ship tracks. Using these estimates, and the position of temperature fronts as an indication of prominent jets in the mean flow, the eddy forcing is shown to be different to that observed in FRAM. Instead of forcing the mean flow, eddies are being generated within the jets which are likely to be maintained by topographic forcing.

Seasonal variations in the behaviour of particle reactive heavy metals in Loch Etive, a fjordic estuary on the West Coast of Scotland, have been investigated using the natural radioactive tracers <SUP>210</SUP>Pb, <SUP>210</SUP>Po and <SUP>234</SUP> Th. A multi-sample (water column samples; sediment traps; short sediment cores) time-series (monthly sampling for eighteen months) study is reported for one station in a stagnant, 140 m deep, basin. In all water samples the distinction between particulate and dissolved was made by filtering through 0.45μm filters. Emphasis has been placed on assessing the post-depositional mobility of Pb in organic-rich, high sedimentation-rate, coastal sediments. There was no renewal of the water in the deep basin during the study period, and the dissolved oxygen concentration gradually fell, to ~2.4 ml<SUP>-1</SUP>. River and rainwater samples were analysed for <SUP>210</SUP>Pb and <SUP>210</SUP>Po in order to determine their input fluxes into Loch Etive. The mean particulate, dissolved and total <SUP>210</SUP>Pb riverine concentrations were 0.43±0.33, 1.14±0.93 and 1.30±1.09 Bq m<SUP>-3</SUP> respectively. The similar <SUP>210</SUP>Po concentrations were 1.77±1.39, 2.60±0.93 and 4.21±3.01 Bq m<SUP>-3</SUP> respectively. The total riverine <SUP>210</SUP>Pb and <SUP>210</SUP>Po flux, averaged over the whole surface of Loch Etive, was 149±125 and 483±345 Bq m<SUP>-2</SUP> year<SUP>-1</SUP> respectively. The mean rainwater total <SUP>210</SUP>Pb and <SUP>210</SUP>Po activities of 53.8±15.2 and 97.5±107 Bq m<SUP>-3</SUP> respectively, result in mean depositional fluxes to Loch Etive of 118±33.5 and 214±235 Bq m<SUP>-2</SUP> year<SUP>-1</SUP> respectively. The relative importance of the riverine input reflects Loch Etive's large catchment area (~2000 km<SUP>3</SUP>). Water column particulate, dissolved and total <SUP>210</SUP>Pb and <SUP>210</SUP>Po concentrations were determined monthly for 17 months. The dissolved/particulate ratio was close to unity, which reflects the large concentration of particulate material in coastal samples. The surface (0-10 m) concentrations, varied greatly, dependent on the amount of run-off in the weeks prior to sampling. The intermediate (10-60 m) and deep (60-120 m) water concentrations were more constant, with <SUP>210</SUP>Pb particulate, dissolved and total means: 0.17±0.09, 0.18±0.14 and 0.36±0.20 Bq m<SUP>-3 </SUP>respectively. The corresponding <SUP>210</SUP>Po means were: 0.15±0.07, 0.27±0.19 and 0.42±0.20 Bq m<SUP>-3</SUP> respectively.

The Cretaceous geological record of the Western Interior Seaway of North America has been extensively studied and suggests a complex and dynamic history of interrelated tectonic, eustatic, oceanographic and climatic changes. This seaway linked the Arctic ocean with the subtropical Tethyan ocean and eustatic fluctuations caused mixing of the two very different water masses affecting the sedimentological and palaeontological record. Extensive work on the lithostratigraphy, biostratigraphy. and geochemistry has resulted in a highresolution chronostratigraphic framework allowing precise bed-by-bed correlation between sections hundreds of kilometres apart. Cenomanian to Turonian strata from four sections and one core, from Arizona, Utah, Colorado and Kansas have been studied for their marine palynomorph and palynofacies assemblages and the biostratigraphy is described. Precise correlation of samples between the sites shows that many biostratigraphically useful taxa have synchronous ranges and that many taxa also had environmental preferences. These are subsequently used for palaeoenvironmental interpretation. Strata from the core record the second-order transgressive-regressive eustatic Greenhorn marine cycle with superimposed third- and fourth-order fluctuations. The range of palaeoenvironments studied here include probable freshwater through near-shore to distal pelagic environments. Foraminifera have long been used in the basin for palaeoenvironmental interpretation and a direct comparison shows that the dinoflagellate cyst assemblages are equally as good at tracing sea-level and water mass fluctuations. A global marine oxygen depletion event is suggested to have occurred at the Cenomanian - Turonian boundary. Integration of palynological data with previous work suggests that burial of amorphous organic matter at this time was related to primary productivity which increased with expansion of the Tethyan water mass at times of third- and fourth-order transgression. This integrated, high-resolution study with tight chronostratigraphic control credits the use of dinoflagellate cysts, not only as a biostratigraphic tool but also with a very real and precise potential for palaeoenvironmental and palaeoecological interpretation.

The Thesis examines some of the aspects of river and estuarial engineering. The derivation of the equation of motion for shallow water waves is discussed and the physical significance of the terms in the equation examined. A review of methods for investigating the problems of estuarial engineering is presented with particular emphasis on the mathematical methods of solution. Two laboratory models were constructed for investigating some of the problems of open channel flow. The results of velocity and depth from the first model were compared with computed values from numerical solutions based on (a) the method of characteristics (b) the explicit finite difference method considering momentum in one dimension only and (a) the explicit finite difference method considering momentum in two horizontal dimensions. method (b) was used to provide comparable results of depth and velocity for the second model. This model included the phenomenon of saline mixing which was investigated theoretically by an explicit finite difference solution to the one dimensional equation of saline diffusion. method (b) was also used to investigate the tidal region of the River Hooghly.

This thesis is mainly concerned with the theoretical prediction of the mass transport velocity in an off-shore tidal current. Other agents that may be responsible for contributions to the existing steady currents are ignored. In the treatment, the fluid system is divided into two regimes a viscous boundary layer, where vertical gradients are considered important and, above this, a region where the motion is, to a first approximation, independent of the depth coordinate. In this uppermost region, the effects of viscosity are neglected. Superimposed on this basic picture, next to the sea-bed, a thin layer is proposed across which there is a rapid transition from laminar to turbulent flow conditions (the laminar sub-layer). Above this layer, the turbulence is assumed to have the same characteristics at all depths, and can be parameterised by using a constant coefficient of eddy-viscosity. The current just above the sea-bed is related to the bottom stress by an empirical quadratic friction law in order to provide an estimate of frictional dissipation. The resulting velocity profiles and the order of magnitude of frictional dissipation at the sea-bed are in good agreement with observation and experiment. A general expression for the horizontal mass transport velocity is derived in the case of constant depth. Using data that is representative of conditions in Liverpool Bay and the eastern Irish Sea, the horizontal mass transport velocity is determined, and it is suggested that the magnitude and direction of this velocity near the bed is closely related to the net movement of any material suspended just above the sea-floor.

A numerical model of the horizontal wind driven ocean circulation is developed, with the aim of considering the influence of frictional dissipation on the flow. The model consists of a time dependent vorticity equation which is integrated from the sea surface to a depth which corresponds to the thermocline. By this procedure the vertical structure of the currents in the upper layer of the ocean is removed, and the vorticity equation is reduced to a two dimensional equation. The forcing mechanism of the flow is provided by the curl of the wind stress at the surface. In order to balance this source of vorticitv , a form of dissipation at the bottom boundary of the model is required.

This thesis is concerned with the two basic modes of barotropic wave motions in rotating fluid: inertia-gravity waves and Rossby waves. The emphasis of the study is on the non-linear aspects of these wave motions. The existence of finite amplitude inertia-gravity wave solutions in the shallow water equations with Coriolis terms is demonstrated. These waves have narrow sharp crests and broad flat troughs as in the case of Stokes' waves but they induce no mass flux and are stable to side-band perturbations. The excitation of inertia-gravity lee waves by mountain barriers is studied both analytically and numerically. Supercritical basic flow is shown to be a necessary but not sufficient condition for the establishment of stationary lee waves. Some new solutions for the Rossby wave equation are obtained. The stability of finite amplitude channel Rossby waves is examined. The stability of the wave is found to depend critically on the aspect ratio (the ratio of the channel width to the wave length) of the wave. Resonant interactions between Rossby waves and inertia-gravity waves are also investigated. Finite amplitude retrogressive inertia-gravity waves are found to be unstable to perturbations of resonantly interacting infinitesimal amplitude Rossby waves and forward propagating inertia-gravity waves.

There is much evidence that El Nino and La Nina (collectively called ENSO) lead to signifIcant atmospheric seasonal predictability across much of the globe. However, despite successful predictions of tropical Pacific SSTs, atmospheric seasonal forecasts have had limited success. Two possible reasons for this lack of skill are considered. Firstly, some errors in an atmosphere only model, HadAM3, are investigated and secondly, the impacts on predictability of the remote SST anomalies teleconnected with EN SO (SST teleconnections) are studied.

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