The hydrodynamics of a relatively deep semi-enclosed micro-tidal stratified coastal embayment and its adjacent waters is investigated through a combination of observational and analytical modelling techniques. The relative importance of hydrodynamic processes influenced by baroclinic and barotropic mechanisms, at time scales from hourly to annual, is detailed. The field site for the investigation is Cockburn Sound and surrounding waters, off southwest Australia. It is shown that for either a homogeneous or two-layered coastal embayment that is separated from the ocean by relatively shallow sill openings, a wind-stress will result in free surface and interface variations which approximate those of a geometrically equivalent closed basin; the similarities become greater as the sills become shallower. This is achieved through the development, validation and application of an analytical hydraulic model of throughflow, free surface and interface variation (ie upwelling), based on the Bernoulli and Momentum theorems. It is demonstrated that simple analytical methods originally developed for the calculation of mean dynamical motions and upper mixed layer deepening in closed basins can be applied, without undue loss of accuracy, for the same purposes in semi-enclosed embayments such as Cockburn Sound. The hydrodynamics of Cockburn Sound and adjacent waters (south to about Wambro Sound) is shown to progress through a characteristic annual cycle, within which it transforms from being a Region of Freshwater Influence (named the Swan-Canning ROFI) during mid-winter to spring, to a Region of Evaporation Influence (named the Perth ROEI) during autumn. The ROFI regime relates to the hydrodynamic influence of strong salinity gradients set up through coastal freshwater buoyancy fluxes derived from estuarine outflows of the Swan-Canning Estuary. The concept of a ROEI regime, which relates to the hydrodynamic influence of strong salinity gradients set up through evaporation and/or hypersaline estuarine discharges, is introduced in this thesis. South of Cockburn Sound, the coastal waters between Dawseville and Warnbro Sound are affected by estuarine discharges from the Peel-Harvey Estuary and local evaporation and hence also undergo a characteristic intra-annual ROFI to ROEI transition. The region is accordingly named the Peel-Harvey ROFI for the mid-winter to spring period and the Peel-Harvey ROEI for the autumn period. The work of this thesis supplements the global understanding ofROFls (Simpson, 1997a) and introduces the concept of the ROEl, through the baseline study of two newly defmed ROEl regimes. It is shown that wind-stress and density gradients are the primary influences on the mean basin-scale hydrodynamic behaviour of Cockburn Sound and its adjacent waters throughout the year. During Cockburn Sound's ROFl regime, full-depth mixing occurs on average about once per synoptic cycle (ie about weekly), when frontal systems, originating in the 'Roaring Forties', bring strong storm winds from the northwest and southwest quadrants (10-15 m s⁻¹). Following these events, the wind pattern tends to southwesterly-southeasterly and weakens <10 m s⁻¹), and deep-water renewal takes place as relatively dense ocean water plunges into the embayment via the sill openings. This results in the establishment of stable vertical stratification, characterised by a parent pycnocline between the relatively dense inflow and resident embayment water. Surface waters are advected out of the embayment. This process continues as the wind remains weak-moderate and swings through the southeast quadrant. The wind then continues to swing through the northeast and northwest quadrants, gradually strengthening to about 10 m s⁻¹, while driving buoyant plumes of brackish Swan-Canning Estuary water southwards into the embayment, assisted by Coriolis force. The cycle then returns to the severe mixing phase, as the next storm front passes the area. Throughout the cycle, notwithstanding severe storm mixing, incomplete vertical mixing of the water column (down to about the depth of the parent pycnocline) occurs via surface processes associated with diurnal winds and penetrative convection. In contrast, during the ROEl regime evaporative processes lead to strong vertical salinity stratification in the embayment, and full-depth mixing is not as regular as during the ROFl regime. Although the average occurrence of storms (which fully mix the embayment) appears to also be, on average, about 4-5 times per month (as per the ROFI regime), the essential factor that was clarified through the observations and analyses is that up to 3 weeks may pass between these events. The mean density of the embayment is greater than that of the adjacent ocean. Hence, mixing within the embayment is followed by relatively buoyant inflows of ocean water. Flushing of the embayment as a whole is therefore less regular than during the ROFl regime, and this influences the poorer water quality (due to eutrophication) that characterises the ROEl regime. During summer (ie between the ROPI and ROEI regimes), seabreezes and penetrative convection regularly mix the water column to the bottom (on almost a daily basis), due to the relatively strong nature of mixing agents and the relatively weak buoyancy fluxes at this time of the year. The analytical and observational clarifications of the hydrodynamic influence of density gradients, both within Cockburn Sound and between the embayment and adjacent ocean, have improved the qualitative and quantitative understanding of the nature and rates of exchange and mixing in these waters. In turn, this has provided a better understanding of the biological characteristics of the embayment, such as the annual occurrence of nuisance algal blooms and de-oxygenation during the ROEI regime. Numerical hydrodynamic models were applied in a major study of the ecology of the Perth coastal zone, ie the Southern Metropolitan Coastal Waters Study (Simpson et al, 1996). The results ofthis thesis guided the choice, application, calibration and validation of the models. It is shown that baroclinic models are appropriate for the relatively strongly stratified ROPI and ROEI regimes, and that barotropic models are suitable otherwise, such as during summer when full-depth mixing occurs almost daily and the density difference between the embayment and adjacent ocean is relatively small.

[Truncated abstract] It has become widely apparent throughout the world that the discharge of nitrogen contaminated groundwater is reducing surface water quality of marine coastal waters, and is subsequently contributing to the decline of benthic habitats such as seagrasses. A process-based understanding of submarine groundwater discharge (SGD) has lagged behind these impacts, and this lack of understanding is addressed by this thesis. This thesis, of the spatial and temporal complexity of SGD, has uncovered and answered questions regarding the sources, fate and transport of SGD in a complex coastal discharge environment. Radium isotope techniques, groundwater biogeochemical investigations and HAMSOM surface water modelling have identified the magnitude, transport and fate of SGD in Cockburn Sound, a semienclosed embayment in Western Australia. A temporal periodicity that encompassed end-of-winter, early-summer, late-summer and mid-winter regimes of hydrology and oceanography, was employed in field studies that spanned the years 2003, 2004 and 2005. ... The fate of the groundwater in the semi-enclosed embayment was investigated using knowledge of surface water currents. Localised regions of high groundwater influence were identified in the surface waters of the embayment, and through the application of a 3-dimensional hydrodynamic model (HAMSOM) it was discovered that, despite similar total volume residence times, variation in the surface flow regime resulted in very different fates for groundwater discharged to the embayment. For three of the four investigated seasonal regimes, groundwater discharged at the shoreline was shown to be rapidly exported out of the embayment (within approximately 1-3 days). During mid-winter very different wind and current regimes existed, resulting in the lateral transport of shoreline groundwater across the embayment, presenting potential for nutrient recirculation within the system for longer time periods (10+ days). Lateral transport of groundwater during mid-winter from the limestone region of the coastline, may contribute to peaks in phytoplankton biomass that have been reported to occur at this time. The investigations into spatial, temporal and biogeochemical dynamics of SGD provided for further dissertation of the processes that affect these dynamics, at a scale that was relevant to marine embayments, coastal aquifers and the coastal ecosystem. It is hoped that this thesis will contribute to a better understanding of the inputs, dynamics and impacts of SGD on coastal ecosystems and lead to improved management strategies for coastal zones.

Conventional bathymetric surveying is a costly and time consuming business. Even today many areas of shallow inshore ocean, some which encompass potential oil and gas fields, are only minimally charted. There is a need for reconnaissance systems which can effectively direct more expensive detailed surveys to best effect. Remote spectral bathymetry is one such system.A review of candidate sensor systems and processing algorithms highlighted problems due to changing bottom cover types and water quality parameters. A method, proposed and theoretically validated by other workers, was chosen for further investigation. This method develops an approximate relationship between the spectral content of the satellite data and water depths and then, by an iterative phase in the spatial domain, seeks to minimise the effect of spatially dependant variations.A study site in Cockburn Sound, Western Australia was chosen for a demonstration of this method. Spectral data are from the Landsat Thematic Mapper instrument and depth data are taken from Admiralty Charts. A variation on the originally proposed algorithm introduces spatial preprocessing phase, in which the image is segmented into zones where spectral relationships are expected to be more uniform. Two different methods of spatial mapping are used.The results demonstrate the capability of spatial modelling to improve remotely sensed depth estimates in the depth range of 5 to 12 m. The need for further research to better understand the shallow water spectral relationships is identified.

Thesis (Ph. D.)--Ohio State University, 2005. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2008 Sep 13

Thèse (Ph.D) -- Université Laval, 2003. / Titre de l'écran-titre (visionné le 29 mars 2004). Bibliogr.

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This bachelor thesis engages in a quest to understand the concepts of necessity and grace in Simone Weils thinking. The question in play, in which many more questions lie hidden, reads as follows: How does Weil understand the operations of grace in relation to the ”blind necessity” of the natural world, and what are the philosophical implications of this concept of grace? What are, for instance, given her understanding of the world as God’s creation, the metaphysical grounds for a basic human activitiy such as thinking or reflexion? A reading of Simone Weils works on necessity, grace, affliction and attention is contrasted with her thoughts on science, method and truth. The concept of necessity is compared to the one of Spinoza, especially on the subject of how the good or the just relates to the true and the necessary: it shows there are interesting similarities and illuminating differences between the two philosophers’ lines of thought. Here, the concept of attention becomes central to the image: the idea of a cultivated mode of reception of the world and of the Other. Attention is analogously understood as a method of prayer and a cultivated ethical attitude towards other human beings – and an ideal scientific state of mind. In the final chapter of the analytic part of the composition, Weils concept of grace is investigated in regard to concepts of thinking and understanding. Here, Leibniz idea of the divine world and the divine mind plays a concise but important role on the matter of a tentative metaphysical grounding of thinking as such – how this can be thought and how it reflects and deepens Simone Weils metaphysics, especially her understanding of the highest states of insight into the nature of the world as partly a work of divine grace. In the last chapter Walter Benjamins vision of the coming philosophy as a consolidation between Immanuel Kants transcendental philosophy and religious experience – and religious thought – show the way for further investigation into the field, a field that the thesis has outlined at the same time as it has attempted to answer some specific questions that seems to be the most urgent ones.

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