Tesi sul tema "Continental shelf"

South Africa has an extensive coastline offshore of which lies the prominent South African continental shelf, a relatively flat extension of the onshore coastal plain. The continental shelf is host to major mineral and petroleum deposits, home to South Africa’s major sea fisheries and full of navigation hazards. Therefore, knowledge of the seafloor features, or bathymetry, of the continental shelf is essential to understanding both its long-term geological evolution and present-day use for resources and navigation. Unfortunately there has been little advancement in our knowledge of the South African continental shelf since the marine studies of the 1970’s and 1980’s which culminated in the “Bathymetry around Southern Africa” map of Dingle et al. (1987). Although bathymetric mapping equipment and techniques have greatly improved during the last few decades, very little high resolution bathymetric data of the South African continental margin are currently available for scientific use, with the majority of the high resolution multi-beam echo-sounding bathymetric surveys being undertaken by privately owned mineral exploration and mining companies (such as De Beers, Alexkor, Petro SA, Petroleum Agency of South Africa, etc.), the Council for Geoscience and the South African Navy and Hydrographic Office. More recent advances in satellite altimetry have had a major impact on ocean floor bathymetric mapping especially in deep ocean areas where the sea surface generally reflects the underlying bathymetry. The Department of Agriculture, Forestry and Fisheries (DAFF) annually collect single-beam echo-sounding data in order to monitor the abundance of fish species along the South African continental shelf and along with that collect seafloor bathymetry as an additional benefit. The aim of this project is to create a detailed bathymetric map of the continental shelf of South Africa by using digital single-beam echo-sounding data collected by the Fisheries Division of the DAFF over the last two decades. The bathymetric dataset of ±7 million single-beam echo-sounding data points was manually processed, gridded and exported to produce a detailed bathymetric map of the entire South African continental shelf between the Orange River mouth and Kosi Bay complemented by Satellite Altimetry data from the ETOPO 1 – 1 Arc-Minute Global Relief Model (Amante and Eakins 2009) for the deep ocean area adjacent to the continental shelf. The single- beam bathymetric data were collected by the F.R.S. Africana II and F.R.S. Algoa vessels using SIMRAD EKS-38, EK 400, EK 500 and more recently the EK 60 single-beam echo-sounders along with a the SIMRAD ES38B split beam transducer. The West Coast and South Coast margins have the greatest bathymetric detail due to DAFF’s Cape Town base of operations, whilst the East Coast margin is less detailed due to fewer research campaigns in this area. The Bathymetric Map of the South African Continental Margin produced in this thesis reveals several new and more detailed bathymetric features. New bathymetric features include the northern extension of the Olifants Valley submarine canyon, details of the rocky inner shelf related to glacial period sea level lowstands, as well as the coast parallel wave cut terraces and palaeo dune ridges on the middle shelf between Cape Seal and Cape Recife. Other prominent bathymetric features such as Childs Bank, Cape Canyon, Cape Point Valley, the offshore submerged river valleys of the Breede and Gouritz Rivers and the east-west trending, basement anticlinal ridges situated at the southernmost extent of the Agulhas Arch were revealed in greater detail by this study. The underlying geology, physical Oceanography, drainage patterns as well as eustatic sea-level fluctuations can all be linked to the bathymetry of the continental shelf, which is why this thesis examines the influences of each of these factors on the seafloor morphology around the South African coastline.

The main objective of this thesis is to unveil the challenges of RCM as an analysis method for assets on the Norwegian continental shelf. A mixed research method have been used, also known as a semi-quantitative method, with gathering of both quantitative and qualitative data from RCM facilitators with relevant experience. A secondary goal with this thesis has been to develop a systematic approach to those who participate in RCM processes, to evaluate their own processes and RCM tools towards applicable standards to generate increased awareness.The primary motivation for maintenance on the Norwegian continental shelf is risk centered, rather than reliability centered. Nevertheless, it is called for RCM, but not all the capacities of RCM to ensure reliability are utilized. There were found several reasons for why this is so.RCM is by many viewed as a resource consuming method. This have led to many attempts in streamlining the process, which often entails crosscuts that threatens the quality of the analysis.Another reason is the lack of data to perform mathematical and statistical evaluations, which implies that nearly all decisions made in the analysis are based on qualitative experiences rather than neutral data. This is a challenge which is hard to overcome when maintenance concepts, assets and processes to analyze are dynamic and will always be subject for change. That should be a good reason for performing living programs, so that the analysis keep track with the changes. However, this is not the case, which means that data will not be gathered either. There is simply no culture for taking use of mathematical and statistical formulae in order to optimize maintenance.RCM depends to a large degree on the humans performing the analysis. This involves personal knowledge of the RCM methodology, software skills, insight and understanding of the assets and systems under review, and an ability to cooperate in a group while carrying out the analysis.The large tag structures on the Norwegian continental shelf that are analyzed with RCM are complex structures that are challenging to keep overview of when performing the analysis. With such large tag structure, it is hard to take notice if an item has changed its identification because such changes are not necessarily updated with the RCM software. This puts the analysis in risk of omitting certain items for the analysis. Also, it is hard to estimate how long it will take to perform an analysis for large tag structures.A method for self-evaluation of RCM processes have been developed for RCM participants in order to ensure increased awareness on important aspects of the RCM methodology and software in use.The work from this thesis can be continued by testing out the survey which has been developed, in order to make this a tool for RCM participants to increase awareness in the processes and the tools they use when performing the analyses.Research could be done within the standardization of methods and criterions for execution of RCM analysis.Future attention should be put on how one can collect data from maintenance for use in mathematical and statistical formulae to ensure living programs for RCM analyses.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998.<br>Includes bibliographical references.<br>by James Maxwell Pringle.<br>Ph.D.

Bibliography: pages 147-155.<br>92 cytheracean species, representing 44 genera are recorded from the Palaeogene Agulhas Bank and west coast margin of South Africa. 11 genera and 3 species are common with the Upper Cretaceous faunas. 12 genera (18 species) are left in open nomenclature. The following genera are represented:- Bythoceratina, Incongruellina, Ruggieria, Eucythere, Krithe, Parakrithe, Eucytherura, Cytheropteron, Ambostracon, Urocythereis, Muellerina, Leguminocythereis, Loxoconcha, Schlerochilus, Poseidonamicus, Bradleya, Agrenocythere, Australileberis, Chrysocythere, Costa, Echinocythereis, Haughtonileberis, Henryhowella, Parvacythereis, Phacorhabdotus, Soudanella, Stigmatocythere, Togoina, Trachyleberis, Veenia, Atlanticythere, Xestoleberis. Data on South African Cretaceous and Palaeogene ostracod faunas are discussed in terms of: faunal associations for the South African Palaeogene JC-1, Agulhas Bank and west coast provinces; characteristic species of Upper Eocene and Upper Eocene to Oligocene strata; generic variations across the Cretaceous/Tertiary boundary. Palaeo-environmental trends from a Cytheracea, Cypridacea + Bairdiacea, Cytherellidae (CCBC) plot indicate a sea level change from <100m (Palaeocene- Eocene), to shallower water with restricted circulation (Upper Eocene) to moderate depth, 100 - 200m (Lower Oligocene). South African faunas are compared with those from adjacent Palaeogene ostracod faunal provinces. Strong generic links occur with West Africa (8 genera in common) and Pakistan (9 genera in common) with only 3 genera in common with Australia and 3 with Argentina.

Doutoramento em Biologia<br>As comunidades de macrofauna bentónica são ecológica e economicamente relevantes, sendo fonte de diversos bens e serviços. A sua identificação, caracterização e mapeamento são importantes para identificar áreas marinhas protegidas e para uma melhor utilização do ambiente marinho. Este trabalho apresenta um estudo holístico da diversidade e distribuição espacial das comunidades de macrofauna bentónica ao longo da plataforma continental Portuguesa. Cerca de 145 locais posicionados ao longo da plataforma ocidental e setentrional foram amostrados com uma draga Smith-McIntyre de área 0,1 m2, a profundidades que variaram entre os 13 e 195 metros. Os sedimentos foram caracterizados em termos de granulometria, de matéria orgânica e geoquímica. São propostos seis habitats bentónicos principais para a plataforma continental Portuguesa, analisada a relação entre os dados biológicos e ambientais e discutidas questões biogeográficas relacionadas com a distribuição espacial de espécies e das comunidades. A distribuição da granulometria e assinatura geoquímica dos sedimentos da plataforma continental revelou-se bastante complexa, refletindo importantes diferenças nas fontes (naturais e antropogénicas), origem fluvial, geomorfologia da plataforma, hidrodinamismo e atividade biológica. Relativamente à macrofauna, entre os mais de 30 mil indivíduos recolhidos, foram identificados cerca de 737 taxa, dos quais quatro são novas espécies e aproximadamente 40 correspondem a primeiras ocorrências para a costa Portuguesa. As espécies mais frequentes foram a Ampharete finmarchica, Ampelisca sp. e Lumbrineris lusitanica sp. nov. enquanto as mais abundantes foram Mediomastus fragilis, Polygordius appendiculatus e Ampharete finmarchica. A abundância por local de amostragem variou entre 7 e 1.307 espécimens e a diversidade alfa atingiu um máximo de 96 taxa. Os sedimentos mais grosseiros apresentaram maior diversidade e abundância comparativamente com os sedimentos envasados. Foram identificados seis habitats bentónicos na plataforma continental Portuguesa: (a) sedimentos grosseiros com Protodorvillea kefersteini, Pisione remota, Angulus pygmaeus e várias espécies intersticiais; (b) areias finas hidrodinamicamente expostas e próximas da linha de costa com Magelona johnstoni, Urothoe pulchella e Angulus fabula; (c) comunidade de Abra alba em areia envasadas da plataforma profunda do noroeste; (d) Galathowenia oculata, Lumbrinerides amoureuxi e outros poliquetas escavadores e tubícolas em areais envasadas muito profundas na plataforma sudoeste; (e) Euchone rubrocincta, Nematonereis unicornis e várias espécies setentrionais nas areias envasadas da plataforma sul; (f) vasas com Sternaspis scutata, Heteromastus filiformis e Psammogammarus caecus. A granulometria do sedimento (particularmente teor em finos), matéria orgânica, profundidade e hidrodinamismo foram as variáveis ambientais com a maior relação com os padrões de distribuição da macrofauna. As espécies cosmopolitas e de latitudes superiores (clima Boreal ou Temperado Frio) dominaram o setor noroeste, sendo substituídas por espécies mais quentes na área de transição entre os canhões da Nazaré e S. Vicente, que dominaram por conseguinte a plataforma sul. O presente estudo evidenciou a abundância e diversidade da macrofauna bentónica ao longo da área costeira de Portugal, na qual coexistem faunas das províncias biogeográficas do norte da Europa, bem como subtropicais. Integrado com outro estudos, este poderá ser a base para uma melhor gestão da plataforma continental Portuguesa.<br>Macrofauna benthic communities are ecologically and economically relevant, providing important ecological goods and services. Their identification, characterization and mapping are important to identify marine protected areas and to an overall better use of the marine environment. This work presents a comprehensive assessment of the diversity and spatial distribution of the soft-bottom benthic macrofauna communities along the Portuguese continental shelf. A total of 145 sites positioned along the west and south coasts of Portugal were sampled with a 0.1 m2 Smith-McIntyre grab, at depths ranging from 13 to 195 metres. Sediment grain-size, total organic matter and bulk geochemistry were characterized. It is proposed six major soft-bottom benthic habitats for the Portuguese continental shelf, analysed the relationship between the macrofauna patterns and environmental variables and discussed the biogeographic issues related to the spatial distribution of species and communities. The sediments grain-size distribution and geochemical signature were complex, reflecting differences in the sources, fluvial input, shelf morphology, hydrodynamic energy and biological activity. Concerning the macrofauna, 737 taxa were identified in more than 30000 specimens. Four new species and nearly 40 new species occurences for the Portuguese coast were recorded in the scope of this work. The most frequent species were Ampharete finmarchica, Ampelisca sp. and Lumbrineris lusitanica sp. nov., while the most abundant were Mediomastus fragilis, Polygordius appendiculatus and Ampharete finmarchica. Abundance per site ranged from 7 to 1307 specimens per 0.1 m2 and alpha diversity reached a maximum of 96 taxa per 0.1 m2. Coarser sediments presented higher diversity and abundance than mud sediments. Six major soft-bottom benthic habitats were identified and characterized: (a) coarse sediments with Protodorvillea kefersteini, Pisione remota, Angulus pygmaeus and other interstitial species (Lusitanean Venus community); (b) Near shore hydrodynamic exposed fine sands with Magelona johnstoni, Urothoe pulchella and Angulus fabula (Boreal Lusitanean Tellina community); (c) Abra alba community in northwestern deep muddy sands (with northern biogeographic affinity); (d) Galathowenia oculata, Lumbrinerides amoureuxi and other burrowers and tubicolous polychaetes in southwestern deep muddy sands (biological community with warmer affinity); (e) Euchone rubrocincta, Nematonereis unicornis and other warmer water species in muddy sands of the southern and sheltered shelf; (f) Muds of Sternaspis scutata, Heteromastus filiformis and Psammogammarus caecus. Sediment grain-size, organic matter, depth and hydrodynamic energy were the variables best related with the macrofauna distribution patterns. Cosmopolitan and northern species (Cold Temperate and Boreal affinity) dominated the northwestern sector, were replaced by warmer species (Lusitanean, Mediterranean and African affinity) in a transition area between the Nazaré and S. Vicente Canyons, which then dominated the southern shelf. The present study highlighted the abundance and diversity of the macrofauna along a coastal area where cold temperate, warm temperate and subtropical faunas can coexist. Integrated with other studies, it can support a better management of the Portuguese coastal shelf.

Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, December 2003.<br>Thesis advisor(s): Thomas H.C. Herbers, Edward B. Thornton. Includes bibliographical references (p. 71-73). Also available online.

A quantitative understanding of the processes controlling sediment transport and deposition across the land/sea interface is crucial to linking terrestrial and marine environments and understanding the formation of marine stratigraphy. The nature and distribution of terrestrial-derived sediment preserved in shelf stratigraphy in turn provides insight into the complex linkages inherent in source-to-sink sediment dynamics. Located inboard of an actively subducting plate boundary and characterized by one of the highest sediment yields in the world, the open-shelf setting off of the Waiapu River in New Zealand presents an excellent location to improve our understanding of the factors controlling the formation of continental shelf stratigraphy and associated sediment transport. Over 850km of high-resolution seismic and swath bathymetry data ground-truthed by cores show significant stratigraphic spatial variation preserved on the Waiapu continental shelf. This spatial variation is likely controlled by regionally-specific sediment deposition and resuspension processes as well as antecedent geology. Chronostratigraphic control obtained from black carbon analysis reveals that deforestation of the Waiapu catchment is preserved as a distinct event in the adjacent inner shelf stratigraphy, and further indicates that the inner shelf is currently capturing a significant ∼16-34% of the total Waiapu sediment budget. Shelf-wide stratigraphy shows that the thickest deposits of Holocene stratigraphy are found in tectonically-created accommodation spaces, highlighting the role of neotectonics in strata formation. The primary control on strata formation on the Waiapu continental shelf is presumed to be tectonically-steered, local sediment supply, which likely still influences modern-day sediment transport via the effects of small-scale bathymetric lows steering gravity-dependent sediment flows at the river mouth.

Ce travail de thèse explore la dynamique à sousmésoéchelle sur le plateau continental du golfe de Gascogne. Dans la première partie, les caractéristiques des processus à sousmésoéchelle sur le plateau sont identifiées à l’aide de données satellites à haute résolution de température de surface de la mer issues du capteur MODIS. Une détection des fronts est réalisées à l’aide d’exposants de singularité, une approche récente pour identifier les irrégularités dans les champs de SST. Les résultats sont complétés par des simulations numériques à 2.5 km de résolution spatiale. Trois types principaux de fronts sont présentés : i) les fronts de marée le long de la côte et plus marqués dans la région d’Ouessant; ii) les fronts au niveau du talus continental liés à l’activité des ondes internes; iii) les fronts d’eaux dessalées aux limites des panaches de rivières en hiver. Dans la seconde partie, un modèle hydrodynamique réaliste du golfe de Gascogne a été mis en place. Cette configuration a une résolution spatiale de 1 km et 40 niveaux verticaux sigma. Un diagnostic est basé sur l’hypothèse que les processus à sousmésoéchelles résultent d’instabilités baroclines. L’énergie potentielle disponible est ainsi convertie en énergie cinétique tourbillonnaire avec des échelles temporelles O(1) jour ou moins grâce à ces processus. L’activité est plus intense dans la région d’Ouessant et les régions côtières en été. En hiver, ces processus ont une échelle temporelle O(1) jour (∼ 30 heures). Ces échelles temporelles sont un indicateur de la présence d’instabilités baroclines à sousmésoéchelle à proximité du panache<br>This thesis explores the submesoscale dynamics in the Bay of Biscay continental shelf. In the first part, submesoscale features over the shelf are identified using remotely sensed high resolution sea surface temperature (SST) images by MODIS. Front detection is achieved through singularity exponents, a novel method of calculating irregularities on the SST fields, and an index for the frontal activity is generated. Results are complemented with 2.5 km horizontal resolution numerical simulations. Three main types of fronts are presented: i) tidal mixing fronts along the coast and most significantly in the Ushant region; ii) shelf break front related to internal tidal wave activity; iii) fresh water fronts along the edge of the river plumes in winter. In the second part, a realistic hydrodynamical model of Bay of Biscay is set up. The model has a 1 km horizontal resolution and 40 σ vertical layers. Diagnostics is based on the assumption that the submesoscale features in the upper ocean are the result of baroclinic instabilities. Available potential energy (APE) is then converted to eddy kinetic energy (EKE) in time scales in O(1) day or less through this process. Activity increases in the Ushant region and the coastal regions in summer, whereas, in winter, activity in the vicinity of the fresh water plumes dominates. In summer, EKE conversion time scale in this region is ∼ 5 days, which can be considered shorter than mesoscale. In winter, they have a time scale of O(1) (∼ 30 hours). This is an indicator that the submesoscale baroclinic instability is happening at the plume

Ce travail de thèse explore la dynamique à sousmésoéchelle sur le plateau continental du golfe de Gascogne. Dans la première partie, les caractéristiques des processus à sousmésoéchelle sur le plateau sont identifiées à l’aide de données satellites à haute résolution de température de surface de la mer issues du capteur MODIS. Une détection des fronts est réalisées à l’aide d’exposants de singularité, une approche récente pour identifier les irrégularités dans les champs de SST. Les résultats sont complétés par des simulations numériques à 2.5 km de résolution spatiale. Trois types principaux de fronts sont présentés : i) les fronts de marée le long de la côte et plus marqués dans la région d’Ouessant; ii) les fronts au niveau du talus continental liés à l’activité des ondes internes; iii) les fronts d’eaux dessalées aux limites des panaches de rivières en hiver. Dans la seconde partie, un modèle hydrodynamique réaliste du golfe de Gascogne a été mis en place. Cette configuration a une résolution spatiale de 1 km et 40 niveaux verticaux sigma. Un diagnostic est basé sur l’hypothèse que les processus à sousmésoéchelles résultent d’instabilités baroclines. L’énergie potentielle disponible est ainsi convertie en énergie cinétique tourbillonnaire avec des échelles temporelles O(1) jour ou moins grâce à ces processus. L’activité est plus intense dans la région d’Ouessant et les régions côtières en été. En hiver, ces processus ont une échelle temporelle O(1) jour (∼ 30 heures). Ces échelles temporelles sont un indicateur de la présence d’instabilités baroclines à sousmésoéchelle à proximité du panache<br>This thesis explores the submesoscale dynamics in the Bay of Biscay continental shelf. In the first part, submesoscale features over the shelf are identified using remotely sensed high resolution sea surface temperature (SST) images by MODIS. Front detection is achieved through singularity exponents, a novel method of calculating irregularities on the SST fields, and an index for the frontal activity is generated. Results are complemented with 2.5 km horizontal resolution numerical simulations. Three main types of fronts are presented: i) tidal mixing fronts along the coast and most significantly in the Ushant region; ii) shelf break front related to internal tidal wave activity; iii) fresh water fronts along the edge of the river plumes in winter. In the second part, a realistic hydrodynamical model of Bay of Biscay is set up. The model has a 1 km horizontal resolution and 40 σ vertical layers. Diagnostics is based on the assumption that the submesoscale features in the upper ocean are the result of baroclinic instabilities. Available potential energy (APE) is then converted to eddy kinetic energy (EKE) in time scales in O(1) day or less through this process. Activity increases in the Ushant region and the coastal regions in summer, whereas, in winter, activity in the vicinity of the fresh water plumes dominates. In summer, EKE conversion time scale in this region is ∼ 5 days, which can be considered shorter than mesoscale. In winter, they have a time scale of O(1) (∼ 30 hours). This is an indicator that the submesoscale baroclinic instability is happening at the plume

Previous experiments to record seismic data at wide angle on the continental shelf have generally been unsuccessful in determining velocity structure in the lower crust; either the lines were too short or shot-receiver density too sparse to identify lower crustal arrivals. In contrast, deep normal incidence profiles show good structural resolution in the crust and uppermost mantle. This dissertation describes a new sea-bottom multichannel instrument which was developed to record datasets containing closely spaced traces to improve the resolution of reversed wide-angle experiments on the continental shelf. The Pull-Up Multichannel Array (PUMA) is a 1200 m, 12 channel, hydrophone array for remotely recording seismic data on the sea-bed. It consists of 12 short hydrophone sections linked by 100 m long passive sections. A pressure case is attached at one end in which recording electronics, cassette tape recorders and a battery power supply are housed. The PUMA is deployed in less than 200 m of water from a research ship and moored to buoys for recovery. The instrument, which was successfully used in an experiment west of Lewis, Outer Hebrides, U.K., was specifically designed to determine a well constrained velocity structure for the crust and uppermost mantle over part of the BIRPS WINCH deep, normal incidence profile. Data recorded by the PUMA show a high signal to noise ratio and it is easy to correlate phases across the record section and to monitor changes in amplitude because traces are closely spaced. A velocity structure for the continental crust and uppermost mantle has been devised using amplitude modelling. The model is interpreted to show that: the upper crust consists of Lewisian gneiss metamorphosed in the amphibolite facies, and contains a low velocity zone which is probably granitic in composition; the middle crustal layer has virtually no velocity gradient; and the lower crust, represented by second arrivals, contains a high velocity gradient and probably consists of granulites. The Moho is at 27.0 ± 0.5 km depth. This is shown to be a layered boundary and it is suggested that this layering is caused by crustal underplating. There is little velocity gradient in the uppermost mantle. This model shows good agreement with the BIRPS WINCH section, although the Moho appears to coincide with the top rather than the base of a band of reflections at 8.3 s two-way travel time on unmigrated WINCH data.

This thesis summarizes and concludes my master thesis research work. The main objective of this research was to develop a rigorous and generic forecast model for all the fields on the Norwegian Continental Shelf based on publically available data and free software. Pipe-It Norwegian Continental Shelf Integrator and Forecaster solution provides the opportunity to forecast oil and gas production rate and economics for all assets on the Norwegian Continental Shelf. The solution is automatically synchronized with an on line database, that is maintained by the Norwegian Petroleum Department. The solution currently contains 87 fields and handles thousands of application launches in parallel. The results can be filtered and aggregated for multiple engineering purposes, like the impact of new discoveries on future production rates and economics.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1987.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN.<br>Vita.<br>Includes bibliographies.<br>by Leslie Karen Rosenfeld.<br>Ph.D.

The Ayeyarwady and Thanlwin Rivers, which primarily drain Myanmar, are together one of the largest point sources of freshwater and sediment to the global ocean. Much of the estimated 600 Mt of river sediment annually carried by the combined Ayeyarwady and Thanlwin River system is delivered to a wide continental shelf in the northern Andaman Sea. Called here the Ayeyarwady-Martaban continental shelf, this area is influenced by strong tides, monsoon conditions, and periodic cyclones; however, the processes that dominate dispersal of fluvial material in the coastal ocean of this system remain poorly understood. The shelf exhibits a dramatic asymmetry of the surface morphology and sediment texture in the east–to–west direction, and recent field observations indicate that sediment accumulation rates increase and then decrease offshore of the western portion of the Gulf of Martaban. A three-dimensional coupled hydrodynamic and sediment transport model was used to explore the oceanographic processes responsible for sediment dispersal off the Ayeyarwady-Thanlwin Rivers. Model runs were developed using ROMS (Regional Ocean Modelling System) and SWAN (Simulating WAves Nearshore) to represent oceanographic conditions in the region and suspended sediment transport. The model setup was applied to two cases: one month representative of the winter northeast monsoon, and one month representative of the summer southwest monsoon. Model estimates of sediment dispersal and transport during summer and winter monsoon conditions were analyzed, and compared to spatial patterns found in field measurements, as well as satellite imaging. Within the Gulf of Martaban, both the surface and bottom currents were strongly tidally driven; therefore, seasonal signals were less prevalent. Over the Ayeyarwady delta region, the seasonal signal was large in both wave energy and surface currents, which had a distinct bidirectional pattern: flowing eastward during the SW monsoon and westward during the NE monsoon. Bottom currents over the Mouths of the Ayeyarwady had less seasonality. During the southwest monsoon, wave energy was higher over the Ayeyarwady Delta, leading to increased resuspension of sediment that was subsequently carried into the Gulf near the coast. Sediment resuspension was strongly tidal-dominated within the Gulf of Martaban, with asymmetric tidal trapping making the Gulf region conducive to high turbidity. During the NE monsoon, the Gulf acted as a "mixing-bowl," where there were high sediment fluxes during flood and ebb tides, but very little net export. Meanwhile, the SW monsoon had high tidal fluxes as well as a large net export of sediment out of the Gulf.

The characteristics and effects of intrusions of estuarine outflow over the inner shelf were examined, based on hydrographic and meteorological observations obtained during the "Coastal Ocean Processes" (CoOP'94) field experiment located off the Outer Banks at Duck, North Carolina. The episodic presence of distinct low salinity water masses issuing from the Chesapeake Bay created an intermittent baroclinic coastal current along the North Carolina coast. Under low wind conditions, this current occupied the upper half of the water column within 9 km of the coast. The plume was bounded by a distinct southward-propagating front, a region offshore of high horizontal salinity and velocity gradients, and a strong pycnocline underneath. The intrusion traveled along the coast at a speed comparable to the linear internal wave speed of a two-layer system. Intrusions were generally associated with southward winds (downwelling conditions); however, several observed events opposed northward wind-driven flow. The geometry and dynamics of the low salinity plume were strongly controlled by the local winds. Northward (upwelling) winds caused the plumes to widen offshore and thin vertically. Southward (downwelling) winds acted initially to speed the intrusions' alongcoast movement and cause them to narrow and deepen. Under strong downwelling winds, however, the intrusions contacted the bottom. This greatly decreased their speeds and caused diffusive widening. Propagation speeds of all plumes were seen to slow steadily through the study region. This was attributed to the observed mixing with ambient water along the path of the intrusion which increased its salinity, thereby reducing the buoyancy forcing. Under the continued influence of upwelling winds, the low salinity intrusions moved rapidly away from the coast and formed shallow lenses floating over the ambient shelf water. These generally dissipated in 1 to 2 days. The theoretical offshore transport response to wind forcing was investigated, illustrating two dynamical behaviors of the plumes, depending on whether they occupied the entire water column or were vertically segregated by stratification. The meteorological control of Bay/shelf exchange was examined to better comprehend the pulsed timing of the low salinity intrusions, which occurred every 2 to 8 days. Estimates of volume flux were derived from temporal variations of waterlevel measurements within the Chesapeake Bay. The volume flux time series exhibited strong peaks of outflow, which preceded the low salinity events off Duck, N.C. by an average of 1.1 days, a time lag consistent with the observed alongcoast propagation speeds.

This thesis shows how Western Australian coast and continental shelf evolved into their present form, in response to changes in sea-level and climate, during the last Glacial Age. I have focused on four contrasting marine environments: the Kimberley coast and offshore islands, Shark Bay, the Swan River estuary and Geographe Bay. In each area, I took a multidisciplinary approach to my data collection and analysis utilising remote sensing, marine geophysics, sedimentological and geochronological methodologies.

Submitted by Caroline Falcao (caroline.rfalcao@ufpe.br) on 2017-06-29T17:18:13Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) 2010-Dissertação-LucianaSobral.pdf: 1105199 bytes, checksum: 5aaf1109d2a55efb90515d9830a5a27e (MD5)<br>Made available in DSpace on 2017-06-29T17:18:13Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) 2010-Dissertação-LucianaSobral.pdf: 1105199 bytes, checksum: 5aaf1109d2a55efb90515d9830a5a27e (MD5) Previous issue date: 2010-02<br>O objetivo desse estudo foi caracterizar a meiofauna e, especialmente,os nematódeos marinhos na Plataforma Continental do Nordeste do Brasil, os quais foram coletados durante o Programa Revizee. As amostras foram obtidas pelo Navio Oceanografico “Antares” da Marinha do Brasil, em realizadas quatro campanhas: I (em 1995), II(em 1997), III (em 1998) e IV (em 2000). Em laboratório, a meiofauna foi extraída pelo método de decantação (com elutriação manual) e peneiramento úmido. Em cada amostra, foram retirados 100 Nematoda para identificação ao nível genérico, através do uso dechave pictorial. Os padrões de distribuição foram analisados considerando-se três fatores (profundidade, campanhas, tipo do sedimento de fundo). A meiofauna foi composta por 22 grupos taxonômicos: Oligochaeta, Polychaeta, Acari, Amphipoda, Cladocera, Copepoda, Cumacea, Isopoda, Ostracoda, Tanaidacea, Bivalvia, Gastropoda, Polyplacophora, Turbellaria, Insecta, Kinorhyncha, Gastrotricha, Nematoda, Priapulida, Rotifera, Sipuncula e Tardigrada. Os Nematoda dominaram nas amostras, representando 43% do total de indivíduos coletados, seguidos dos Copepoda (35%) e Polychaeta (12%). Um total de 7865 nematódeos foram identificados e distribuídos em oito ordens (Enoplida, Triplonchida, Chromadorida, Desmodorida, Desmoscolecida, Monhysterida, Araeolaimida and Plectida), 37 famílias e 170 gêneros. As famílias Desmodoridae, Chromadoridae e Xyalidae mostraram os maiores números de gêneros. Considerando as diferentes campanhas, 28 gêneros representaram mais de 70% do total dos Nematoda estudados. A profundidade foi o único fator que mostrou significância na estrutura da comunidade. Entretanto, informações da literatura indicam que essa variável poderia estar, indiretamente, refletindo outras variáveis, como a disponibilidade de alimento.<br>The goal of this study was characterized the meiofauna and, specially, marine nematodes at the northeastern Brazil continental shelf, which were collected during the REVIZEE program. Samples were obtainedby the oceanographic vessel "Antares" Navy of Brazil, in four campaigns: I (in 1995), II (in 1997), III (in 1998) and IV (in 2000). In the laboratory, meiofauna was separated by decantation (with agitation) method and wet sieving. In each sample, one hundred individuals of nematodes were picked out for identification at genus level, using a pictorial key. The distribution patterns were analyzed considering three factors (depth, campaigns, bottom sediment type). Meiofauna was composed by 22 groups: Oligochaeta, Polychaeta, Acari, Amphipoda, Cladocera, Copepoda, Cumacea, Isopoda, Ostracoda, Tanaidacea, Bivalvia, Gastropoda, Polyplacophora, Turbellaria, Insecta, Kinorhyncha, Gastrotricha, Nematoda, Priapulida, Rotifera, Sipuncula and Tardigrada. Nematodes were dominant in the samples, representing 43% of the total individuals, followed by Copepoda (35%) and Polychaeta (12%).A total of 7865 nematodes were identified and distributed in eight orders (Enoplida, Triplonchida, Chromadorida, Desmodorida, Desmoscolecida, Monhysterida, Araeolaimida and Plectida), 37 families and 170 genera. The families Desmodoridae, Chromadoridae and Xyalidae showed the highest number of genera. Considering the different campaigns, 28 genera represented 70% of the total of studied nematodes. The depth was the only factor that showed a significant on the community structure. Although, literature information indicated that this variable could be, indirectly, reflected other variables, like food available.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Includes bibliographical references (p. 257-267).<br>The water circulation and evolution of water temperature over the inner continental shelf are investigated using observations of water velocity, temperature, density, and bottom pressure; surface gravity waves; wind stress; and heat flux between the ocean and atmosphere during 2001-2007. When waves are small, cross-shelf wind stress is the dominant mechanism driving cross-shelf circulation. The along-shelf wind stress does not drive a substantial cross-shelf circulation. The response to a given wind stress is stronger in summer than winter. The cross-shelf transport in the surface layer during winter agrees with a two-dimensional, unstratified model. During large waves and onshore winds the crossshelf velocity is nearly vertically uniform, because the wind- and wave-driven shears cancel. During large waves and offshore winds the velocity is strongly vertically sheared because the wind- and wave-driven shears have the same sign. The subtidal, depth-average cross-shelf momentum balance is a combination of geostrophic balance and a coastal set-up and set-down balance driven by the cross-shelf wind stress. The estimated wave radiation stress gradient is also large. The dominant along-shelf momentum balance is between the wind stress and pressure gradient, but the bottom stress, acceleration, Coriolis, Hasselmann wave stress, and nonlinear advection are not negligible. The fluctuating along-shelf pressure gradient is a local sea level response to wind forcing, not a remotely generated pressure gradient. In summer, the water is persistently cooled due to a mean upwelling circulation. The cross-shelf heat flux nearly balances the strong surface heating throughout mid-summer, so the water temperature is almost constant. The along-shelf heat flux divergence is apparently small. In winter, the change in water temperature is closer to that expected due to the surface cooling. Heat transport due to surface gravity waves is substantial.<br>by Melanie Rinn Fewings.<br>Ph.D.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 209-215).<br>Observations from a three-year field program on the inner shelf south of Martha's Vineyard, MA and a numerical model are used to describe the effect of stratification on inner shelf circulation, transport, and sediment resuspension height. Thermal stratification above the bottom mixed layer is shown to cap the height to which sediment is resuspended. Stratification increases the transport driven by cross-shelf wind stresses, and this effect is larger in the response to offshore winds than onshore winds. However, a one-dimensional view of the dynamics is not sufficient to explain the relationship between circulation and stratification. An idealized, cross-shelf transect in a numerical model (ROMS) is used to isolate the effects of stratification, wind stress magnitude, surface heat flux, cross-shelf density gradient, and wind direction on the inner shelf response to the cross-shelf component of the wind stress. In well mixed and weakly stratified conditions, the cross-shelf density gradient can be used to predict the transport efficiency of the cross-shelf wind stress. In stratified conditions, the presence of an along-shelf wind stress component makes the inner shelf response to cross-shelf wind stress strongly asymmetric.<br>by Rachel Mandy Horwitz.<br>Ph.D.

O presente trabalho de investigação visa caraterizar a segurança da plataforma continental nacional, segundo a dimensão de segurança (safety e security) e a dimensão de conhecimento científico. A justificação do tema é sustentada por argumentos que decorrem das atuais circunstâncias em que o país se encontra: profunda crise financeira com impacto na segurança; uma multiplicidade de entidades e organismos do Estado com atribuições nos espaços marítimos nacionais; quatro entidades com meios para atuar no mar; a falta de articulação; a obsolescência e falta de meios e capacidades; e a limitada capacidade de vigilância marítima. Sendo portanto oportuno efetuar a caraterização das capacidades e meios nacionais e dos fatores determinantes para a segurança da plataforma continental nacional. Em termos metodológicos o design da investigação consiste no “Estudo de Caso”, uma vez que permite efetuar uma análise detalhada e intensiva do objeto de estudo. A estratégia de pesquisa é mista (quantitativa e qualitativa) e o raciocínio de análise hipotético-dedutivo. Foram ainda efetuadas entrevistas diretivas ou semiestruturadas a personalidades com responsabilidades na segurança da plataforma continental pertencentes a entidades e/ou organismos do Estado. Concluímos que, não obstante as capacidades e meios nacionais de vigilância remota possuírem limitação na cobertura espacial dos espaços marítimos, e os meios oceânicos de patrulha e fiscalização e de conhecimento científico se encontrem obsoletos e serem atualmente insuficientes ou inexistentes, Portugal, tem vindo a garantir a soberania e a jurisdição dos espaços marítimos nacionais. No entanto, se não se investir na continuidade destas capacidades, o país corre risco de não garantir autonomamente a segurança e o conhecimento científico da plataforma continental, ficando dependente dos parceiros da UE e/ou da OTAN, transformando-se, nestas circunstâncias, num Estado protegido. Abstract: The aim of this research is to characterize the security in the national continental shelf, according to the security dimension (safety and security) and the dimension of scientific knowledge. The rationale behind this theme is supported by arguments arising from the current circumstances of the country: severe financial crisis with impact on security; a multitude of entities and state agencies with responsibilities in the national maritime areas; four entities with means to act at sea; lack of coordination; obsolescence and lack of resources and capabilities; and the limited maritime surveillance capability. In these circumstances is appropriate to conduct a survey of the capabilities and national means and the factors that determine the national security of the continental shelf. Methodologically the research design is the "Case Study", since it allows detailed and intensive analysis to the observed state entities and organizations. The research strategy is mixed (quantitative and qualitative), and the reasoning analysis hypothetical-deductive. We’re also, carried out, semi-structured interviews to individuals from state entities and/or organizations with responsibilities in the security of the continental shelf. We conclude that, although the national capabilities and means for monitoring the maritime spaces remotely have a limited coverage, and the ocean means for patrol, boarding and scientific surveys are obsolete and currently lacking or insufficient, Portugal has guaranteed the security of the continental shelf. However, for the continuity of these capacities, economic effort should be done. The fail in the security, planning and ordering of the continental shelf, Portugal can become dependent on the EU and / or NATO partners and, under these circumstances, can become a protected state and loses Sovereignty at sea.

Ocean warming near the Antarctic ice shelves has critical implications for future ice sheet mass loss and global sea level rise. A global climate model with an eddying ocean is used to quantify the mechanisms contributing to ocean warming on the Antarctic continental shelf in an idealized 2xCO(2) experiment. The results indicate that relatively large warm anomalies occur both in the upper 100 m and at depths above the shelf floor, which are controlled by different mechanisms. The near-surface ocean warming is primarily a response to enhanced onshore advective heat transport across the shelf break. The deep shelf warming is initiated by onshore intrusions of relatively warm Circumpolar Deep Water (CDW), in density classes that access the shelf, as well as the reduction of the vertical mixing of heat. CO2-induced shelf freshening influences both warming mechanisms. The shelf freshening slows vertical mixing by limiting gravitational instabilities and the upward diffusion of heat associated with CDW, resulting in the buildup of heat at depth. Meanwhile, freshening near the shelf break enhances the lateral density gradient of the Antarctic Slope Front (ASF) and disconnect isopycnals between the shelf and CDW, making cross-ASF heat exchange more difficult. However, at several locations along the ASF, the cross-ASF heat transport is less inhibited and heat can move onshore. Once onshore, lateral and vertical heat advection work to disperse the heat anomalies across the shelf region. Understanding the inhomogeneous Antarctic shelf warming will lead to better projections of future ice sheet mass loss.

A detailed palynological examination was made of Tertiary pollen and spore assemblages from six exploratory wells located along the continental margins of the Labrador Sea. From north to south, the study wells are Kangamiut 1, Hekja 0-71, Karlsefni A-13, Herjolf M-92, Roberval K-92 and Cartier D-70. Using local extinction events of zonally diagnostic species to define the tops of intervals, eight provisional pollen and spore zones were established. The zones and their relative ages are as follows: Tsuga igniculus (middle to late Miocene); Fagus granulata (early to middle Miocene); Parviprojectus sp. A (early Oligocene); Araliaceoipollenites megaporifer (latest Eocene/earliest Oligocene); Rhoipites latus (middle to late Eocene); Pistillipollenites mcgregorii (early to middle Eocene); Tricolpites sp. A (middle to late Paleocene); and Paraalnipollenites alterniporus (early to middle Paleocene). The middle and upper Oligocene is apparently absent in the study welIs. When used in conjunction with dinoflagellate assemblages, the zonation provides the potential for additional biostratigraphic resolution in the Tertiary marine sediments of the Labrador Sea. It is especially useful in upper Eocene and stratigraphically higher sections in which pollen and spores are the dominant component of the palynoflora: In addition, the basic similarity of pollen and spore assemblages across much of northern and western Canada suggests the zonation may also be successfully applied in those regions. The relative abundance and distribution of four major populations (i.e., Paleozoic, Upper Jurassic/Lower Cretaceous, Upper Cretaceous and Paleogene) of redeposited palynomorphs were determined. The species composition of recycled and in-situ Paleogene palynomorphs supports independent clay mineralogical data that much of the sediment (including a high percentage of the palynomorphs) was delivered to offshore Labrador Sea basins via a "super" river system that drained a large portion of the western interior and Arctic regions of Canada during the Tertiary. The taxonomic composition of the indigenous Paleogene pollen and spore flora supports both paleontological and isotope data that relatively high paleotemperatures prevailed at high northern latitudes during the Paleogene. The climatic optimum in the Labrador Sea region was reached in the early to early-middle Eocene.<br>Science, Faculty of<br>Earth, Ocean and Atmospheric Sciences, Department of<br>Graduate

A total of 186 samples taken from 9 offshore Central & Southern North Sea boreholes, 1 onshore XJK borehole, 2 onshore UK localities and 2 onshore Danish localities were processed and analysed for microfauna. A total of 273 individual taxa were identified - the majority to species level. The dominant microfaunal group recorded are the Foraminifera of which 23 genera were agglutinated, 75 calcareous benthonic and 21 planktonic. Other groups recorded are the Ostracoda which comprised 5 genera, Diatomacea 2 and Radiolaria 1. The recorded taxa are diagnosed and their stratigraphic and palaeoenvironmental significance discussed. The samples range in age from Late Cretaceous (Maastrichtian) through Paiaeocene (Danian &amp; Thanetian) to Early Eocene (Ypresian) and occasionally Middle Eocene (Lutetian). The offshore boreholes are biostratigraphically zoned with respect to the published biozonation scheme of King, 1989, and the so-called 'bioevents' (i.e. microfossil marker horizons) described by Mudge &amp; Copestake, 1992. The emphasis of the study was placed on the stratigraphical distribution of the microfaunas, particularly in the offshore realm where the majority of the boreholes (7) are located in the Southern North Sea area (Quadrants 44 and 49); a region lacking in previously published research on microfaunas of this age. The biozonation scheme of King, 1989, is found to be broadly applicable to all of the boreholes studied although some dififerences m detail were noted. Not all of the bioevents of Mudge &amp; Copestake (1992) are recorded. The samples studied are insuflBciently closely spaced to permit the construction here of a separate biozonation scheme, specific to the Southern North Sea area, although it is considered that the future creation of such a scheme could be justified with additional data. A total of 53 individual microfossil marker horizons thought to have stratigraphic utility in the area are noted. The bulk of the Paiaeocene sediments deposited in the Southern North Sea area were laid down under moderate palaeodepths (c. middle shelf) and probably representative of the socalled 'outer sublittoral' biofacies of King, 1983. Evidence for progressive deepening of water depth towards the north of the area and mto the Silver Pit Basin was noted. The microfaunal assemblages from the offshore boreholes are similar in overall character to microfaunas recorded from onshore Palaeogene sections in the UK and Denmark.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2000.<br>Includes bibliographic references.<br>The bottom boundary layer is an important dynamical region of shallow water flows. In this thesis, the problem of turbulent mixing in the coastal bottom boundary layer is investigated with a unique set of field measurements of velocity and sound speed that span a significant fraction of the boundary layer obtained over a six-week long period in the late summer of 1996 on the New England shelf. The energetics of the turbulent fluctuations are investigated by testing simplified budgets for turbulent kinetic energy and scalar variance. The turbulent kinetic energy budget is locally balanced while the scalar variance budget is not, probably due to turbulent diffusion. The direct effects of stratification are consistently significant only in the outer part of the boundary layer, where the flux Richardson number is approximately equal to a critical value of 0.2. Turbulence closure is investigated in terms of non-dimensional profiles of velocity and sound speed. Close to the bottom, the results are consistent with Monin-Obukhov similarity theory, while in the outer part of the boundary layer other scales including the height of the boundary layer are important for setting the turbulent length scale.<br>by William J. Shaw.<br>Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.<br>Includes bibliographical references (leaves 221-229).<br>The application of a technique to instantaneously image and continuously monitor the abundance, spatial distribution, and behavior of fish populations over thousands of square kilometers using Ocean Acoustic Waveguide Remote Sensing (OAWRS) is demonstrated with data from its first implementation in a 2003 field experiment off the US Continental Shelf south of Long Island, NY. Conventional methods for monitoring fish populations rely on highly-localized, point measurements made from slow-moving research vessels that survey along widely spaced line transects to cover the vast ocean environments that fish inhabit and so significantly under-sample fish populations in time and space. This leads to incomplete, ambiguous and highly-aliased records of fish abundance and behavior. In contrast, OAWRS surveys at a rate roughly one million times greater than that of conventional fish-finding methods. Within a minute and a half, OAWRS images the ocean environment over more than ten thousand square kilometers, an area similar to the state of Massachusetts. This is possible because OAWRS exploits the natural capacity of the continental-shelf environment to act as a waveguide where sound waves are efficiently propagated over long ranges (tens of kilometers) via trapped modes that suffer only cylindrical spreading loss rather than the spherical spreading loss suffered in the short-range (hundreds of meters), waterborne propagation paths employed by conventional fish-finding sonar (CFFS). In this thesis, a method is developed for estimating the instantaneous population density and abundance of fish populations from wide-area OAWRS imagery.<br>The OAWRS population density estimates are calibrated with simultaneous local CFFS measurements, and are used to estimate the expected scattering cross section of an individual fish at OAWRS frequencies so that population density may be estimated in regions where CFFS measurements were not made. It is shown that the OAWRS population density estimates have uncertainties of less than 25% at each pixel or spatial resolution cell, for statistically stationary populations. Instantaneous abundance estimates then have much lower uncertainties when OAWRS population density is integrated over tens to hundreds of independent spatial resolution cells by the law of large numbers. A number of discoveries are also documented about the instantaneous horizontal structural characteristics, temporal evolution, short-term volatile behavior and propagation of information in very large fish shoals containing tens of millions of fish and spanning several kilometers in spatial extent. The OAWRS approach should enable new abilities in the study and assessment of fish populations and their behavioral dynamics.<br>by Deanelle T. Symonds.<br>Ph.D.

Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2007.<br>Includes bibliographical references (p. 177-186).<br>Observations of current velocity, temperature, salinity and pressure from a 2-year moored array deployment and four hydrographic cruises conducted by the United States Southern Ocean GLOBEC program on the western Antarctic Peninsula continental shelf are used to characterize the ocean circulation and its connection to fresh water and heat fluxes on the shelf. Mean velocities on the shelf are of the order of 5 cm/s or less. Tidal motions are dominated by the M2 and S2 semi-diurnal tides and the 01 and K1 diurnal tides, although the tidal velocities are typically less than 2 cm/s. Near-inertial motions are relatively large, with current velocities as high as 26 cm/s. It is shown that Marguerite Trough, a large bathymetric feature connecting the shelf-break to Marguerite Bay, plays a critical role in determining the circulation. The mean flow is strongly steered in the along-slope direction, and the tidal currents also show increasing current polarization at depth in Marguerite Trough. At time-scales of 5 to 20 days, the observations show bottom-intensified motion in Marguerite Trough consistent with bottom-trapped topographic Rossby waves.<br>(cont.) The subtidal circulation in the trough has a significant wind-driven component in Marguerite Trough, with downwelling-favorable winds forcing cross-shelf flow on the northern side of the trough and along the shore on the outer shelf. Upwelling-favorable winds force roughly the opposite circulation. The cyclonic circulation on the trough helps advect blobs of salty, warm and nutrient-rich water across the shelf. These intrusions are small (;4 km) and frequent (4 events/month). Also, the Antarctic Peninsula Coastal Current (APCC), a coastal buoyant current which is described for the first time here. The APCC is a seasonal current which is only present during the ice-free season and is forced by freshwater fluxes associated with large glacier melt and precipitation rates in the region.<br>by Carlos F. Moffat Varas.<br>Ph.D.

Idealized bathymetries were subjected to idealized cyclones in order to measure the storm surge response to a range of bathymetry features, under various storm conditions. Ten bathymetries were considered, including eight shoals, one pit, and a featureless reference domain. Six storms (two different sizes/intensities and three different landfall directions) were used as meteorological forcing. The bathymetry features influenced local surge response during pre- and post-peak surge conditions. However, peak surge and surge at the coast were not meaningfully affected by the presence of the bathymetry features considered. The effect of three bathymetry feature parameters on surge response was analyzed (i.e. depth below mean sea level, cross-shore width, and distance from shore). Of these parameters, feature depth below mean sea level was the most influential on surge generation.

Cold-water coral (CWC) habitats dwell on continental shelves, slopes, canyons, seamounts, and ridge systems around the world’s oceans, from 50 m to depths up to 4000 m. CWC species provide heterogeneous habitats supporting a myriad of associated fauna and form highly diverse CWC reefs and CWC gardens. Main threats, currently impacting CWC ecosystems come from anthropogenic stressors, such as fishing activities, oil and gas exploitation and the incipient mining activity. Likewise, climate change, causing changes in the water column, is also affecting these ecosystems. Life-history traits of CWC species (long lifespans, slow growth and limited recruitment) make them very vulnerable to current and potential threats. Given their limited recovery capacity, interest to preserve and restore CWC ecosystem is steadily growing. The creation of Marine Protected Areas and active ecological restoration actions are nowadays the best management tools to conserve native ecosystems and represents an opportunity to revert the anthropogenic damage that has already taken place. Through passive (natural regeneration after the cessation of stressors) and active (human interacts with biotic and/or abiotic ecosystem features) approaches, restoration activities seek to accelerate the recovery of ecosystem structure and functioning relative to a reference model. Contrarily to terrestrial and shallow-water marine ecosystems, ecological restoration in intermediate (50 – 200 m) and deep marine (> 200 m) environments has received lesser attention. To date, only few restoration actions at local scales have been carried out at those depths, mainly due to technical and economic limitations which questions its wide application. Scaling-up restoration actions and make them affordable are the main present challenges for CWC restoration. In this sense, in order to move forward towards the conservation of intermediate and deep-sea ecosystems, the general aim of the present thesis is to assess the impact of fishing activity on CWC gardens as well as to explore the feasibility of novel active ecological restoration techniques. All the work performed during this thesis has been carried out at the Cap de Creus marine area (North-Western Mediterranean Sea), specifically at the continental shelf (60 – 130 m), where gorgonians, sponges, and sea pen species form CWC gardens supporting a variety of mobile associated fauna. The target species is the yellow gorgonian Eunicella cavolini (Koch, 1887) which dominate in the area forming density patches. In the first chapter, the impact of artisanal fishing was quantified to evaluate the threat of this activity on CWC gardens and to provide essential information to mitigate such impact. The rest of chapters (2, 3 and 4) evaluated, for the first time, the viability to actively restore degraded E. cavolini populations. Specifically, in the second chapter, gorgonians obtained from bycatch (accidentally caught of non-target species) of local artisanal fishers, were transplanted to artificial structures deployed on the continental shelf (805 m). This pilot study demonstrated, for the first time, the high survival of E. cavolini transplants. Following, and going one step forward, in the third chapter, field experiments and modeling approaches were combined to develop and technically validate an innovative large-scale and cost- effective restoration method for CWC gardens. Successful results evidenced the feasibility of recovering bycatch E. cavolini and returning them to their natural habitat with this novel method so-called “badminton method”. Finally, in the fourth and last chapter, a large- scale restoration action of E. cavolini populations was carried out in collaboration with local artisanal fishers during two consecutive fishing seasons by applying the technique previously developed. A large number of gorgonians (460 colonies) were successfully reintroduced and survived at the end of the action (2 years) at 80-100 m depth. The results suggested an initial establishment of a new gorgonian population, which will potentially evolve toward a comparable natural population in terms of size and spatial structure, if natural recruitment also occurs. Moreover, an economic evaluation was performed, also confirming the cost efficiency of this method aimed at enhancing the recovery of impacted CWC gardens. The lack of knowledge of some key ecological processes of CWC ecosystems as well as the technical limitations hinder a complete evaluation of restoration efforts performed. However, this thesis represents a promising improvement for the conservation and recovery of CWCs that could be extended to other areas and regions.<br>Els coralls d’aigua freda habiten en les plataformes continentals, talussos, canyons, muntanyes submarines i dorsals oceàniques d’arreu del món, des de 50 a 4000 metres de profunditat. Les espècies de coralls d’aigua freda creen hàbitats heterogenis que donen suport a una infinitat de fauna associada i formen esculls i boscos de coralls altament diversos. Les principals amenaces que actualment impacten aquests ecosistemes de coralls d’aigua freda son d’origen antròpic, com ara l’activitat pesquera, l’explotació de petroli i gas i l’incipient explotació minera. Així mateix, el canvi climàtic, el qual provoca canvis en la columna d’aigua, també està afectant aquests ecosistemes. Les característiques vitals dels coralls d’aigua freda (longevitat, creixement lent i reclutament limitat) els fan molt vulnerables a les amaces tan actuals com futures. Atesa la seva limitada capacitat de recuperació, l’interès per preservar i restaurar els ecosistemes de coralls d’aigua freda està en constant creixement. La creació d’àrees marines protegides i les accions restauració ecològica activa són avui en dia les millors eines de gestió per conservar ecosistemes autòctons i representen una oportunitat per revertir els danys antròpics que ja han tingut lloc. A través d’enfocaments passius (regeneració natural després del cessament del impacte) i actius (l’ésser humà interacciona amb les característiques biòtiques i/o abiòtiques de l’ecosistema), les activitats de restauració busquen accelerar la recuperació de l’estructura i funcionament dels ecosistemes en funció a un model de referència. Contràriament als ecosistemes terrestres i d’aigües someres, la restauració ecològica enfocada a ambients marins intermedis (50–200 m) i profunds (> 200 m) ha rebut menor atenció. Fins ara, a aquestes profunditats només s’han dut a terme algunes poques accions de restauració a escala local, principalment a causa de limitacions tècniques i econòmiques que qüestionen la seva àmplia aplicació. Els principals reptes actuals per la restauració de coralls d’aigua freda són incrementar l’escala espacial de les accions de restauració i fer-les econòmicament més assequibles. En aquest sentit, per avançar en la conservació dels ecosistemes de fons intermedis i profunds, l’objectiu general de la present tesi és avaluar l’impacte de l’activitat pesquera sobre els boscos de coralls d’aigua freda i explorar la viabilitat de innovadores tècniques de restauració activa. Tot el treball realitzat en aquesta tesi s’ha dut a terme a la zona marina del Cap de Creus (Nord-Oest del mar Mediterrani), contretament a la plataforma continental (60 – 130 m) on espècies de gorgònies, esponges i plomalls formen boscos de coralls d’aigua freda donant suport a una gran varietat de fauna mòbil associada. L’espècie objectiu és la gorgònia groga Eunicella cavolini (Koch, 1887) la qual domina a la zona formant denses agregacions. En el primer capítol, es va quantificar el impacte de la pesca artesanal per avaluar l’amenaça d’aquesta activitat sobre els boscos de coralls d’aigua freda i proporcionar informació essencial per mitigar aquest impacte. La resta de capítols (2, 3 i 4) van avaluar, per primera vegada, viabilitat de restaurar activament les poblacions degradades de E.cavolini. Especificament, en el segon capítol és van trasplantar les gorgònies capturades accidentalment pels pescadors artesanals de la zona, a estructures artificials fondejades a la plataforma continental (85 m). Aquest estudi pilot va demostrar per primera vegada l’alta supervivència dels transplantaments d’E.cavolini. Seguidament, i anant un pas més enllà, al tercer capítol es van combinar experiments de camp i modelització per desenvolupar i validar tècnicament una nova tècnica de restauració per als boscos de coralls d’aigua freda, a gran escala i econòmicament assequible. Els exitosos resultats van evidenciar la viabilitat de recuperar les colònies de E.cavolini capturades accidentalment i retornar-les al seu hàbitat natural amb aquesta innovadora tècnica , anomenada “el mètode bàdminton”. Finalment, al quart i últim capítol, es va dur a terme una acció de restauració de les poblacions de E.cavolini a gran escala, amb la col·laboració de pescadors artesanals de la zona i al llarg de dues temporades de pesca consecutives aplicant la tècnica desenvolupada anteriorment. Un gran nombre de gorgònies (460 colònies) van ser re-introduïdes amb èxit i van sobreviure al final de l’acció (2 anys) a 80-100 m de profunditat. Els resultats van suggerir l'establiment inicial d'una nova població gorgònies, que potencialment evolucionarà cap a una població natural comparable en termes d’estructura de talles i estructura espacial, sempre i quan es produeix també un reclutament natural. D'altra banda, es va fer una avaluació econòmica, que va confirmar la rendibilitat d'aquest mètode dirigit a millorar la recuperació dels boscos de coralls d’aigua freda impactats. El desconeixement d'alguns processos ecològics claus en els ecosistemes de coralls d’aigua freda, així com les limitacions tècniques, dificulten una avaluació completa dels esforços de restauració realitzats. Tanmateix, aquesta tesi suposa una millora prometedora per a la conservació i recuperació dels coralls d’aigua feda, que es podria estendre a altres zones i regions.

Several attributes of the last British-Irish Ice Sheet (BIIS) make it a potentially important analogue to marine-based sectors of modern ice sheets, which are sensitive to oceanic and climatic changes and unstable during the current global climate warming. However, limitations on knowledge of the last BIIS's marine termini hinder the use of this ice mass in comparative assessments or modelling. This research addresses this critical knowledge gap through multiproxy examinations of BIIS marine landforms, sedimentation and ice-proximal palaeoenvironments. A multifaceted examination of the outer shelf (Porcupine Bank and Slyne Trough) using geomorphology, sedimentology and geochronology provides the first confirmation of BIIS shelf-wide extension during the last glaciation (Late Midlandian/Late Devensian) west of Ireland. Multivariate biofacies examinations from the outer shelf suggest the introduction of relatively warm and saline Atlantic water following BIIS decoupling and ice shelf formation. Shelfwide analyses of glacigenic deposits (till and glaciomarine) and landforms (moraines and grounding-zone wedges) provide the first estimates of BIIS marine-margin retreat rates and detailed reconstructions of BIIS marine-margin behaviour west of Ireland. These analyses reveal a major stillstand (<3,300 years) that punctuated overall retreat and deposited a large (~IS0-km long) grounding-zone wedge. Prior to this stillstand, the BIIS was stabilised by a buttressing ice shelf and its grounding line retreated at ~ 74 km/yr; following the stillstand and the loss of the buttressing ice shelf, the BIIS marine-margin retreated to the modern western Irish shoreline at an accelerated rate of ~ 113 m/yr. Radiocarbon analyses of glacitectonised glaciomarine sediment record the first evidence of an Irish ice mass readvancing offshore during the Nahanagan (Younger Dryas) Stadia. Shelf-wide palaeoenvironmental assessments using both novel and well-established multivariate and statistical techniques elucidate a previously unknown, likely climate-driven readvance (the Galway Lobe readvance) and suggest that initial BIIS marine-margin retreat was forced by climate or ocean warming.

Late Quaternary deposits have been investigated from three main study areas from 'western Britain in an attempt to define lithological and biostratigraphic changes. Detailed analyses of included benthonic foraminiferal assemblages are presented and a systematic section included which describes and illustrates over 200 distinct forms. Chronostratigraphic control is provided by radiocarbon dates, amino acid analysis and tephrachronology. The three study areas yield distinctive records of the depositional environments characterizing the climatic events of the Late Quaternary. From the Hebridean Shelf, B.G.S. vibrocores have been analysed within the context of a previously established seismostratigraphic sequence. Foraminiferal faunas allow the reconstruction of a regional climatostratigraphic sequence for the Lateglacial period (c. 14,000 to 10,000 BP) and this sequence is correlated, through 9 radiocarbon (AMS) dates, to the established climatostratigraphy of the Lateglacial period from N.W. Europe. Reconstructions of notional water depths during this period allow glacio-isostatic components from the shelf to be estimated and these confirm a generally accepted pattern of changing relative sea-level, from initial regression following deglaciation and subsequent transgression as the eustatic component over-takes the isostatic component. Rising sea-levels are most notable after about 10,000 BP. A cliff section at Aberdaron on the western Lleyn Peninsula provides an insight into the controversy surrounding the question of depositional origin of the "Irish Sea Drift" sequences bordering the Irish Sea. Diamicts and sorted layers from the section contain mixed boreo-arctic, temperate and pre-Quaternary species, and allochthonous/autochthonous elements are identified. While lithological changes within the section are marked, the foraminiferal assemblages maintain relatively constant faunal ratios. None of the foraminifera are considered to be in situ, but instead entrained by the Irish Sea glacier during its passage along the Basin and deposited at the site by basal melt-out processes. The third study area, the southwestern Celtic Sea, records geomorphological evidence of previously extensive glaciation in the region. Microfaunas, both foraminifera and Ostracoda, are analysed and record a transition from grounded ice lodgement facies to quiet, glacial marine facies at about 49°30 N. Amino acid analysis confirms the geomorphological evidence for glacial marine accumulation during the Late Devensian.

An experiment conducted over the shoreface at Duck, North Carolina in 1985 embraced both fair-weather low energy and storm-related high energy conditions. to differentiate the diffusion and advection processes of suspended sediments under the high energy conditions from those under the low energy conditions, numerical modeling and the analysis of field data are exercised. A simple two-layer eddy viscosity wave-current combined boundary layer model is developed. The modeled characteristics of the boundary layer are incorporated with a diffusion equation to give suspended sediment concentration profiles. A velocity scale related to factors other than turbulent diffusion is formulated, representing the diffusion under varying energy conditions. With increasing bed friction, the vertical diffusion of sediment is reduced due to stratification, thus reducing velocity. From the measured suspended sediment concentration profiles, the resuspension coefficient, &\gamma&, shows a tendency to decrease with increased flow intensity, suggesting the role of the armoring effect. The coefficient, &\gamma&, varies between 0.0003 for high-energy conditions and 0.002 for low-energy conditions. The energetics approach to predicted sediment transport overestimates the role of wave transport for the low energy conditions. Cross-correlations between cross-shore velocity and sediment concentration show that the role of wave for the transport under low energy conditions is not substantial. The direction of transport under low energy conditions is governed by the mean current. Under high energy conditions, transport by waves is onshore but superseded by offshore transport by the mean current, resulting in net offshore transport. The energetics model based on the surfzone dynamics underestimates the transport rate by an order of magnitude compared to the depth integration of the average product of mean cross-shore velocity and mean concentration. This indicates that the calibration of the efficiency factors &\epsilon\sb{lcub}\rm s{rcub}& and &\epsilon\sb{lcub}\rm b{rcub}& in an energetics model is essential.

This thesis examines the emerging health and safety regulatory regime in Ghana's nascent upstream petroleum industry putting it in context with the approaches that have evolved in the United Kingdom Continental Shelf and the United States Outer Continental Shelf. The thesis analyses the existing regulatory framework in Ghana in terms both of the architecture and of the orientation of health and safety regulation. As regards the regulatory architecture, it concludes that it is characterised by fragmented agencies under piecemeal legislation. This has resulted in regulatory overlap and lacunae. Also, the regulatory agencies including the emerging upstream regulator are saddled with conflicting missions of resource exploitation and oversight of health and safety. The thesis further demonstrates that these agencies lack decision making independence and therefore cannot provide the independence and visibility required for a robust health and safety regime. Whereas the current regulatory challenge faced by Ghana has been experienced previously in the UKCS and the US OCS, and steps have been taken there to resolve the problem of conflicting functions, the precise approach differs in each case. But the degree to which the principle of separating functions has been observed in each case may be said to correlate with the robustness of the regime in question. As regards regulatory orientation, the thesis concludes that each of the three jurisdictions examined adopts a different approach: Ghana's is basically self-regulatory while the US OCS approach is prescriptive and the UKCS framework is characterised by goal-setting and process regulation. The thesis evaluates the three approaches and concludes that the management-based approach built in to the safety case of the UKCS has proved to be robust against the prescriptive performance-based approach of the US. The thesis therefore proceeds to recommend the adoption of the UK's approach for Ghana so that all the fragmented industry specific agencies and legislation would be replaced with a single independent and visible authority and a single goal setting legislation for occupational health and safety.

The Waiapu River drains a small mountainous basin, characterized by steep terrain, heavy rainfall, and unconsolidated soft Tertiary mudstone and siltstone. These factors, combined with heavy deforestation over the past 100 years have created one of the world's highest sediment yields. Water discharge of the Waiapu River is very episodic over both inter- and intra-annual timescales, and almost all of the discharge is associated with floods brought by cyclonic storms. The Waiapu River drains an active margin that has a narrow shelf and steep slope. Marine conditions on the Waiapu continental shelf are very energetic, with strong waves as well as shelf currents. This special river-ocean system makes the Waiapu area an ideal site to study gravity-driven flows. Instrumented tripods deployed at water depths of 40 m and 60 m on the Waiapu shelf directly offshore of the river mouth recorded data on waves, currents, and sediment fluxes from May through August, 2004. The tripod data showed direct field evidence of current-supported gravity flows on the Waiapu shelf. Data analysis indicated that the Waiapu River floods were characterized by two distinct phases: a flood phase and a resuspension phase. The flood phase was characterized by large sediment input, coupled with moderate to strong waves but weak currents. Strong near-bed sediment signals, however, were not recorded by the tripods until the post-flood resuspension phases, during which seaward near-bed currents started to intensify. A one-dimensional boundary layer model provided the inference that those strong seaward near-bottom turbid flows during the resuspension phase were dynamically similar to wave-supported gravity flows observed on Eel and Po Shelves, except that both waves and currents were important for sediment resuspension. In contrast to thin and dense wave-supported gravity flows, current-supported gravity flows on the Waiapu shelf were significantly thicker and more dilute. Another two-dimensional model for wave- and current-supported sediment gravity flows was used to estimate sediment deposition on the Waiapu shelf from September 2003 to August 2004. The time period for the model calculations was divided into two segments: a low-energy (September to May) and high-energy portion (May to August). Model results showed that sediment delivered by the Waiapu River were trapped between the 20- and 80-m isobaths during the low-energy period, but then redistributed obliquely across the shelf between the 60- and 120-m isobaths during the high-energy period. Depositional locations estimated for the low- and high-energy portions, respectively, matched well with short- and long-term observed accumulation patterns based on 7 Be and 210Pb activity as reported by Kniskern (2007; Kniskern et al. 2008). Sensitivity analysis indicated that the gravity-driven flows on the Waiapu shelf were mainly wave-supported landward of the 40-m isobath, but became increasingly current-supported as wave orbital decayed in deeper water. This dissertation provided the first documentation of current-supported gravity flows, and hence contributed greatly to the study of sediment transport on continental shelves.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior<br>This study embraces the west continental shelf of Cearà (147 samples of marine sediments) and two fluvial courses (4 sediment samples of Curu and SÃo GonÃalo rivers) to determine heavy minerals distribution with their possible provenances and economic potential. Sedimentary facies on the continental shelf were distinguished through the particle size and calcium carbonate content. Heavy minerals were investigated for their total content (%), relative abundance (%) of each mineral species, concentration in Kg/ton of predominant species, mineralogical index (RZi and ZRT) and grains imaging by SEM-EDS. In geoprocessing obtained the spatial distribution of data by Arcgis 10.1 and Surfer 10 got informations about bottom morphology of the continental. Multivariate analysis were included using Statistica 7.0 to aid in the interpretation of results. Heavy minerals were concentrated in Fortaleza chart (contents reached to 4.54%) at depths until 20 m in the litoclastic and litobioclastic sands. Among the 18 mineral species identified, ilmenite and tourmaline were embracing most of the continental shelf and with epidote and monazite presented content > 1 Kg/ton near SÃo GongaÃo do Amarante coast. Paleochannels and ancient beach-ridge were identified. The occurrence of typical regional metamorphic mineral paragenesis of rocks rich in aluminum suggests the provenance of Cearà Complex rocks (primary source) that occur both near the coast and outcrops directly on the continental shelf. Reworked sediments of Barreiras Formation, beach black sands and longshore drift sediments (secondary sources) contribute regionally in heavy mineral supply.Curu river influences ilmenite, tourmaline and epidote supply. Multivariate analyzes and RZi/ZTR variations corroborated with the dual nature provenance (primary and secondary) of the continental shelf sediments and expose a mixture of recente sediments with older reworked ones.<br>Este estudo abrange a plataforma continental oeste do Cearà (147 amostras de sedimentos marinhos) e dois cursos fluviais (4 amostras de sedimentos dos rios Curu e SÃo GonÃalo) para determinar a distribuiÃÃo dos minerais pesados com suas possÃveis proveniÃncias e potencial econÃmico. Distinguiram-se as fÃcies sedimentares da plataforma continental pela granulometria e teor de carbonato de cÃlcio. Os minerais pesados foram investigados pelos seus teores totais (%), abundÃncias relativas (%) de cada espÃcie mineral, teores em Kg/ton das espÃcies predominantes, Ãndices mineralÃgicos (RZi e ZRT) e imageamento dos grÃos por MEV-EDS. No geoprocessamento obteve-se a espacializaÃÃo dos dados pelo Arcgis 10.1 e informaÃÃes da morfologia de fundo da plataforma continental com o Surfer 10. IncluÃram-se anÃlises multivariadas por meio do Statistica 7.0 para auxiliar na interpretaÃÃo dos resultados. Os minerais pesados se concentraram na folha Fortaleza (teores de atà 4,54%) em atà 20 m de profundidade e nos domÃnios das areias litoclÃsticas e litobioclÃsticas. Dentre as 18 espÃcies minerais identificadas, a ilmenita e a turmalina foram as que abrangeram a maior parte da plataforma continental e juntamente com epÃdoto e monazita apresentaram teores > 1 Kg/ton prÃximo à costa de SÃo GonÃalo do Amarante. Foram identificados paleocanais e antigas linhas de praia. A ocorrÃncia da paragÃnese mineral tÃpica de metamorfismo regional de rochas ricas em alumÃnio sugere a proveniÃncia das rochas do Complexo Cearà (fonte primÃria) que ocorrem tanto prÃximo à costa como afloram diretamente na plataforma continental. Sedimentos retrabalhados da FormaÃÃo Barreiras, areias pretas praiais e sedimentos de deriva litorÃnea (fontes secundÃrias) contribuem regionalmente no aporte de minerais pesados. O Rio Curu exerce influÃncia no aporte de ilmenita, turmalina e epÃdoto. As anÃlises multivariadas e as variaÃÃes de RZi e ZTR corroboraram com a proveniÃncia de natureza dual (primÃria e secundÃria) dos sedimentos plataformais, alÃm de expor uma mistura de sedimentos recentes com sedimentos retrabalhados mais antigos.