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1
Elfadli, Kasem. "Indian Ocean Dipole impacts on northwestern Indian Ocean climate variability." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/396586/.
Full textAbstract:
The Indian Ocean Dipole (IOD) is a coupled ocean-atmosphere phenomenon in the equatorial Indian Ocean, with a positive mode characterized by anomalous warming of sea surface temperatures in the west and anomalous cooling in the east. The IOD has been shown to affect inter-annual variability of the Indian monsoon. There is also evidence that the IOD may affect the formation, strength and duration of monsoon-related oceanic features in the North West Indian Ocean (NWIO), including fronts and eddies, the Somali upwelling and the ‘Great Whirl’ system. However, the mechanism by which the IOD develops and details of its connection with monsoon-related oceanic phenomena in the NWIO remain unclear. Satellite datasets of sea surface temperature anomalies (SSTA) and sea surface height anomalies (SSHA) over the past two decades have been examined, mainly to investigate the relationship between the IOD and large-scale climate modes like the Indian monsoon, El Niño Southern Oscillation (ENSO) and Rossby/Kelvin Waves. Early results show SSHA in NWIO; is more correlated with the IOD than with the ENSO. Also the results indicate an impact of Rossby wave patterns on the Somali Current system. Satellite datasets of sea surface temperature anomalies (SSTA) and sea surface height anomalies (SSHA) over the past two decades have been examined, mainly to investigate the relationship between the IOD and large-scale climate modes like the Indian monsoon, El Niño Southern Oscillation (ENSO) and Rossby/Kelvin Waves. Early results show SSHA in NWIO; is more correlated with the IOD than with the ENSO. Also the results indicate an impact of Rossby wave patterns on the Somali Current system. Satellite datasets of sea surface temperature anomalies (SSTA) and sea surface height anomalies (SSHA) over the past two decades have been examined, mainly to investigate the relationship between the IOD and large-scale climate modes like the Indian monsoon, El Niño Southern Oscillation (ENSO) and Rossby/Kelvin Waves. Early results show SSHA in NWIO; is more correlated with the IOD than with the ENSO. Also the results indicate an impact of Rossby wave patterns on the Somali Current system.
2
Haynes, Annette M. "Indian naval development power projection in the Indian Ocean? /." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242460.
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Thesis (M.S. in National Security Affairs)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Winterford, David. Second Reader: Wood, Glynn. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): India, Naval Plalnning, Military Forces (United States), Military Force (Foreign), Foreign Policy, Pakistan, China, Indian Ocean, Power Projection, Theses. Author(s) subject terms: India, Pakistan, China, United States, Soviet Union, Foreign Policy, Military, Indian Naval Development, Power Projection. Includes bibliographical references. Also available in print.
3
Gibbons, Ana D. "Regional plate tectonic reconstructions of the Indian Ocean." Thesis, The University of Sydney, 2012. http://hdl.handle.net/2123/8580.
Full textAbstract:
This thesis outlines and tackles the major outstanding issues of early Indian Ocean plate tectonic reconstructions using recent advancements in data and technology. The first chapter is focussed on the original extent of Greater India, using information from the abyssal plains offshore West Australia to incorporate tectonic boundaries that include several major submarine plateaus. In this chapter we also describe the methods employed to construct our plate kinematic models. The second chapter investigates the seafloor off East Antarctica, relating it to the conjugate seafloor off East India, where there are several anomalous tectonic features, with disputed origins. This chapter also solves the enigmatic, curved fracture zones located several kilometres off West Australia and East Antarctica, and predicts a diachronous separation between Madagascar and India. The final chapter investigates the implications of the plate reconstruction model further afield, matching the accretions of Greater India, Argoland and various Tethyan oceanic arcs, to the geological evidence in the Eurasia and Southeast Asian margins.
4
Hermes, Juliet C. "Ocean model diagnosis of variability in the South Indian Ocean." Doctoral thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/8649.
Full textAbstract:
Includes bibliographical references (leaves 180-195).Evidence exists that sea surface temperature (SST) variability in the South Indian Ocean may significantly influence weather and climate patterns in the southern African region. SST, in tum, can be influenced by variability in ocean fluxes, observations of which are limited in the South Indian Ocean and it is necessary to augment them with estimates derived from models. Two sets of variability in this region are examined in this thesis. The first concerns the large-scale interannual variability of the oceans neighbouring South Africa and the second, inter-ocean fluxes south of Africa on meso-through to interannual timescales. In terms of the former, a global ocean model forced with 50 years of NCEP (National Centre for Environmental Prediction) re-analyses winds and heat fluxes, has been used to investigate the evolution and forcing of interannual SST variability in the South Indian Ocean and co-variability patterns in the South Atlantic. Secondly, an eddy- permitting model is used to investigate volume, heat and salt fluxes in the oceanic region south of Africa and the effect of variations in the strength of wind forcing. Interannual dipole-like SST variability in the South Indian and South Atlantic Oceans were realistically simulated using the global ocean model, ORCA2. The model results imply that there are connections between large-scale modulations of the midlatitude atmospheric circulation of the Southern Hemisphere and co-evolving SST variability in the South Atlantic and South Indian Oceans. The atmospheric variability results in an increase (decrease) in strength of the anticyclonic wind fields over each ocean during positive (negative) dipole events. The resulting wind anomalies lead to changes in surface heat fluxes, short wave radiation, meridional Ekman heat transport and upwelling, all of which contribute to the evolution of these SST dipole patterns. Evidence is found of links between these dipole patterns and the Antarctic Oscillation and ENSO (El Niño Southern Oscillation).
5
Flaviani, Flavia. "Microbial biodiversity in the southern Indian Ocean and Southern Ocean." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25058.
Full textAbstract:
The multi-phylotype and ecologically important community of microbes in aquatic environments ranges from the numerically dominant viruses to the diverse climate-change regulating phytoplankton. Recent advances in next generation sequencing are starting to reveal the true diversity and biological complexity of this previously invisible component of Earth's hydrosphere. An increased awareness of this microbiome's importance has led to the rise of microbial studies with marine environmental samples being collected and sequenced daily around the globe. Despite the rapid advancement in knowledge of marine microbial diversity, technical difficulties have constrained the ability to perform basin wide physical and chemical oceanographic assessments in tandem with microbiological screening with the majority of studies only looking at a single component of the microbial community. In this study the full microbial diversity, from viruses to protists, was characterised within the southern Indian Ocean and the Southern Ocean from a small volume of seawater collected using the same CTD equipment used by oceanographers. Throughout this study it will be demonstrated how this small volume is sufficient to describe the core microbial taxa in the marine environment. The application of a bespoke bioinformatics pipeline, integrated with sequencing replication, improved the description of the dominant core microbiome whilst removing OTUs present due to PCR and sequencing artefacts thereby improving the accurate description of rare phylotypes. Analyses confirmed the dominance of Cyanobacteria, Alphaproteobacteria and Gammaproteobacteria in the pelagic prokaryotic microbiome, while the Stramenopiles-Alveolata-Rhizaria (SAR) cluster dominates the eukaryotic microbiome. A decrease in the SAR community will be reported for the Southern Ocean with a concomitant increase in the haptophyte community. Whilst the virome confirmed the dominance of tailed phages and giant viruses across all stations, there was a significant variation caudoviruses and Nucleocytoplasmic Large DNA viruses (NCLDV) across defined biogeographical boundaries. The described method will allow the characterisation of the microbial biodiversity as well as future integration with oceanographic data with a much reduced sampling effort. The characterisation of the whole microbial community from a single water sample will improve the understanding of microbial interactions and represent a step towards in the inclusion of viruses into biogeochemical models.
6
Rana, Haris Sarwar. "Indian Ocean surface circulations and their connection to Indian Ocean dipole, identified from Ocean Surface Currents Analysis Real Time (OSCAR) data." Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://handle.dtic.mil/100.2/ADA483452.
Full textAbstract:
Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2008.Thesis Advisor(s): Chu, Peter C. "June 2008." Description based on title screen as viewed on August 26, 2008. Includes bibliographical references (p. 67-71). Also available in print.
7
Ly, Tio Fane-Pineo Huguette. "Chinese diaspora in Western Indian Ocean /." [Rose Hill : [Mauritius] : Mauritius] : Éditions de l'Océan Indien ; Chinese catholic mission, 1985. http://catalogue.bnf.fr/ark:/12148/cb36631208d.
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8
Que, Wen Jun. "String of pearls, myth or reality? : Sino-Indian interaction in Indian Ocean." Thesis, University of Macau, 2012. http://umaclib3.umac.mo/record=b2595577.
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9
Sparrow, Michael Dylan. "Current structure of the South Indian Ocean." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309941.
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10
Tabrez, Ali Rashid. "Slope sedimentation around the NW Indian Ocean." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295607.
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11
Krishnan, Tharishini. "Emerging security paradigm in the Eastern Indian Ocean Region : a blue ocean of Malaysia-India Maritime Security Cooperation." Thesis, King's College London (University of London), 2017. https://kclpure.kcl.ac.uk/portal/en/theses/emerging-security-paradigm-in-the-eastern-indian-ocean-region(8d16846f-34c0-4c0b-b986-4c90d09f28c5).html.
Full textAbstract:
This study investigates the emergence of Malaysia-India Maritime Security Cooperation (MIMSC) in response to traditional threats and non-traditional security threats at the Eastern Indian Ocean Region (EIOR). This thesis argues that although both Malaysia and India have identified the maritime significance of the EIOR to them, the common threat faced by them in that region, and have recognised the need for cooperation in maritime security, it appears at present that MIMSC in EIOR projects a lack of robustness in its engagement. This is despite both an appreciation of the relations between the two countries, and a substantial ability to address the challenges of the EIOR. The positive relations that are challenged by these maritime threats show that there is a pressing need for both countries to draw up effective maritime policies. But it is as yet unclear why these countries have failed to do so. The paucity of scientific investigation into the question of why the two states have failed to draw up an effective maritime policy cooperation despite their potential to do so, and the lack of availability of substantive arguments, turn this question into a significant field of academic inquiry. In order to address this issue, this thesis will ask three sub-questions, relating to: a) the drivers of MIMSC in EIOR, b) the emerging areas of maritime cooperation in mitigating traditional and non-traditional threats in EIOR, and c) the critical factors that would contribute towards a successful MIMSC in EIOR. It will cover the dynamics of MIMSC from the post-Cold War era in EIOR, and draw more substantial answers to how MIMSC in post-Cold War period is a ‘missed opportunity’ but projects a ‘promising opportunity’ to address issues of maritime security threats in the EIOR. Qualitative research design is employed in this research inquiry. This research has used two primary data collection method: a) in-depth personal interviews and b) focus group interviews. Informants were selected through purposeful sampling, focusing on high-ranked retired and serving officials from the Navy, Ministry of Defence, Ministry of Foreign Affairs, maritime security agencies, and think tanks. This research used the NVIVO 10 software program to conduct a Thematic Content Analysis (TCA) to analyse data obtained through interviews. Several emerging areas of maritime collaboration are shaping MIMSC in the EIOR such as: a) partnership in search and rescue operation, b) humanitarian assistance and disaster relief, b) increasing interoperability of constabulary role, c) partnership in defence industry, and d) partnership in maritime resources and competence. These areas of maritime collaboration are highly dependent on major critical success factors such as: a) shaping both formal and informal bilateral and multilateral maritime cooperation, b) overcoming bureaucracy and statutory bottlenecks, c) shared cost-benefit and d) change in maritime strategic thinking.
12
Boersch-Supan, Philipp Hanno. "The ecology of scattering layer biota around Indian Ocean seamounts and islands." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/11440.
Full textAbstract:
The waters of the open ocean constitute the largest living space on Earth but despite its obvious significance to the biosphere, the open ocean remains an unexplored frontier. With a regional focus on the Indian Ocean, this thesis investigates (i) the distribution of pelagic biota on basin scales, (ii) the effect of abrupt topography on pelagic biota and their predator-prey relationships, and (iii) the use of genetic techniques to elucidate population connectivity and dispersal of pelagic taxa. (i) Pelagic scattering layers (SLs) were surveyed with scientific echosounders across the southwest (SWIO) and central Indian Ocean to investigate their vertical and geographical distribution. Structurally distinct SL regimes were found across the Subantarctic Front, and may explain recently observed foraging behaviours of southern elephant seals. Regression models indicated a close relationship between sea surface temperature and mean volume backscatter, with significantly elevated backscatter in the subtropical convergence zone. The heterogeneous distribution of scattering layer biota may have implications for predator foraging and carbon cycling in the Indian Ocean. (ii) Acoustic surveys revealed diverse interactions between SLs, aggregations and topography around islands as well as shallow ( < 200m) and intermediate (200-800m) seamounts at spatial scales from 1 to 100 km. Epi-and mesopelagic backscatter was increased around reefs and banks of the Chagos archipelago, indicating connectivity between oceanic and neritic systems. SWIO seamounts harboured summit-associated aggregations, but the distributions of surrounding SLs did not follow a general pattern. Downstream SL depletion was observed in one location and combined with stomach content analyses, provides an insight into the mechanics of prey flux between open-ocean and seamount ecosystems. (iii) A mitochondrial marker was used to assess the population structure and demography of the hatchetfish Argyropelecus aculeatus in the SWIO. The results are suggestive of a single, well-connected population and indicate a recent population expansion around 0.14 million years ago. This highlights that even highly abundant mesopelagic populations are vulnerable to global climatic changes. Dispersal and recruitment are key ecological processes structuring seamount communities and are directly relevant for the management of exploited populations. Genetic barcoding was evaluated as a means to identify cryptic larval specimens of eels (leptocephali) and spiny lobsters (phyllosomata). Identification success was limited, but indicated the presence of 3-4 phyllosoma clades and 5-6 leptocephalus clades along the SWIR.
13
Senan, Retish. "Intraseasonal Variability Of The Equatorial Indian Ocean Circulation." Thesis, Indian Institute Of Science, 2004. https://etd.iisc.ac.in/handle/2005/297.
Full textAbstract:
Climatological winds over the equatorial Indian Ocean (EqlO) are westerly most of the year. Twice a year, in April-May ("spring") and October-December ("fall"), strong, sustained westerly winds generate eastward equatorial jets in the ocean. There are several unresolved issues related to the equatorial jets. They accelerate rapidly to speeds over lms"1 when westerly wind stress increases to about 0.7 dyne cm"2 in spring and fall, but decelerate while the wind stress continues to be westerly; each jet is followed by westward flow in the upper ocean lasting a month or longer.
In addition to the semi-annual cycle, the equatorial winds and currents have strong in-traseasonal fluctuations. Observations show strong 30-60 day variability of zonal flow, and suggest that there might be variability with periods shorter than 20 days in the central EqlO. Observations from moored current meter arrays along 80.5°E south of Sri Lanka showed a distinct 15 day oscillation of equatorial meridional velocity (v) and off-equatorial zonal velocity (u). Recent observations from current meter moorings at the equator in the eastern EqlO show continuous 10-20 day, or biweekly, oscillations of v. The main motivation for the present study is to understand the dynamics of intraseasonal variability in the Indian Ocean that has been documented in the observational literature.
What physical processes are responsible for the peculiar behavior of the equatorial jets? What are the relative roles of wind stress and large scale ocean dynamics? Does intraseasonal variability of wind stress force intraseasonal jets? What is the structure and origin of the biweekly variability? The intraseasonal and longer timescale variability of the equatorial Indian Ocean circulation is studied using an ocean general circulation model (OGCM) and recent in
Abstract ii
situ observations. The OGCM simulations are validated against other available observations. In this thesis, we document the space-time structure of the variability of equatorial Indian Ocean circulation, and attempt to find answers to some of the questions raised above.
The main results are based on OGCM simulations forced by high frequency reanalysis and satellite scatterometer (QuikSCAT) winds. Several model experiments with idealized winds are used to interpret the results of the simulations. In addition to the OGCM simulations, the origin of observed intraseasonal anomalies of sea surface temperature (SST) in the eastern EqlO and Bay of Bengal, and related air-sea interaction, are investigated using validated satellite data.
The main findings of the thesis can be summarized as:
• High frequency accurate winds are required for accurate simulation of equatorial Indian
Ocean currents, which have strong variability on intraseasonal to interannual time scales.
• The variability in the equatorial waveguide is mainly driven by variability of the winds;
there is some intraseasonal variability near the western boundary and in the equatorial
waveguide due to dynamic instability of seasonal "mean" flows.
• The fall equatorial jet is generally stronger and longer lived than the spring jet; the fall
jet is modulated on intraseasonal time scales. Westerly wind bursts can drive strong
intraseasonal equatorial jets in the eastern EqlO during the summer monsoon.
• Eastward equatorial jets create a westward zonal pressure gradient force by raising sea
level, and deepening the thermocline, in the east relative to the west. The zonal pressure
force relaxes via Rossby wave radiation from the eastern boundary.
• The zonal pressure force exerts strong control on the evolution of zonal flow; the decel
eration of the eastward jets, and the subsequent westward flow in the upper ocean in the
presence of westerly wind stress, is due to the zonal pressure force.
• Neither westward currents in the upper ocean nor subsurface eastward flow (the ob
served spring and summer "undercurrent") requires easterly winds; they can be gener
ated by equatorial adjustment due to Kelvin (Rossby) waves generated at the western
(eastern) boundary.
• The biweekly variability in the EqlO is associated with forced mixed Rossby-gravity
(MRG) waves generated by intraseasonal variability of winds. The biweekly MRG wave in has westward and upward phase propagation, zonal wavelength of 3000-4500 km and phase speed of 4 m s"1; it is associated with deep off equatorial upwelling/downwelling.
Intraseasonal SST anomalies are forced mainly by net heat flux anomalies in the central and eastern EqlO; the large northward propagating SST anomalies in summer in the Bay of Bengal are due to net heat flux anomalies associated with the monsoon active-break cycle. Coherent variability in the atmosphere and ocean suggests air-sea interaction.
14
Mawren, Daneeja. "Upper ocean variability and tropical cyclones in the South West Indian Ocean." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29219.
Full textAbstract:
Tropical cyclones (TCs) are the most devastating weather phenomenon in nature with the powerful storm surge events occurring when severe and large TCs make landfall along coastlines. Although there have been significant strides in the TC track forecasts over the last 30 years, skills in TC intensity prediction still lag behind. Intensity may be impacted by the mixing length temperature (known as Tdy) and barrier layer thickness (BLT). Similar to cyclones in other tropical ocean basins, tropical cyclones in the South West Indian Ocean also cause significant social and economic damage in southeastern Africa and Madagascar. To forecast TC intensity more accurately, monitoring upper ocean conditions in the South Indian Ocean is of top priority. Two areas in the relatively poorly studied South Indian Ocean where such upper ocean characteristics of relevance to tropical cyclones need to be better understood are the Seychelles Chagos Thermocline Ridge (SCTR) and the Mozambique Channel. In the first part of the study, the variability of Tdy and BLT in the South West Indian Ocean, focused on the SCTR region and their relationships with tropical cyclones are investigated. It is shown that rapid cyclone intensification is influenced by large Tdy values, thick barrier layers and the presence of anticyclonic eddies. Both BLT and Tdy fields are modulated by the westward propagation of Rossby waves, which are often associated with ENSO. For example, the 1997-1998 El Nino shows a strong signal in Tdy, SST and BLT over the South West Indian Ocean. After this event, an increasing trend in Tdy occurred over most of the basin which may be associated with changes in atmospheric circulation. A rise in SST, Power Dissipation Index and frequency of Category-5 tropical cyclones also occurred post-1998. A case study of TC Bansi in the South West Indian Ocean and its relation to upper ocean heat content was presented. This tropical cyclone is of interest due to its unusual track and also because of all the damage it caused. Anomalously deep thermocline and high Tdy values were observed around December 2014-January 2015 in the South West Indian Ocean and analysis of the upper ocean structure during Bansi showed that its rapid intensification to Category 4 was related to its passage over a high Tdy (warm core) eddy region and a deep barrier layer. The second area focussed on, the Mozambique Channel, is not only a region of relatively high TC activity with highly vulnerable coastal populations, but also very energetic in terms of mesoscale ocean eddies and tidal forcing. Changes in upper ocean characteristics in the Mozambique Channel due to tidal forcing are examined as they may have significant impacts on the upper ocean structure and thus influence tropical cyclones which often occur in this region. Two experiments were conducted using the Regional Ocean Modelling System (ROMS); one forced with tides (Tide) and the other experiment without tidal forcing (NoTide). On seasonal time scales, the tidal forcing simulation shows warmer temperatures in the upper layer particularly near strong ocean currents (North East Madagascar Current and South East Madagascar Current). In Tide, warming near these currents is intensified during winter due to the southeast trade winds, while in summer, poleward advection of warmer waters south of 16-17 oS seemed more prominent. On weather time scales, these changes in the upper ocean structure, especially near the coast or in shallow regions can alter the intensity of passing tropical cyclones. When a storm encounters a warm anticyclonic eddy, as the case of TC Japhet studied in the thesis, the SST cooling by the cyclone is substantially reduced, the mixing length temperature is increased and the mixed layer is deepened. These changes can be important for TC evolution. SST variability over the South West Indian Ocean influences southern African summer rainfall and the regional atmospheric circulation either through regional modes as well as influences the landfall frequency of tropical cyclones on Mozambique (Vitart et al., 2003). Besides SST, a link has recently been found between the regional precipitation over southern Africa and tropical cyclone heat potential (a measure of upper ocean heat content) in the South West Indian Ocean (Malan et al., 2013). In this study, the relationships between an index of southern African summer rainfall (SARI) and Tdy in the South Indian Ocean at zero (January-March) and one season (October-December) lag were analyzed. A region in the southern Mozambique Channel, termed as Tdysmc, showed the strongest positive correlation with SARI at zero lag. Another strong but negative correlation with SARI at one season lag is found in the core of the Seychelles Chagos Thermocline Ridge region, termed as Tdycsctr. Composite analysis (neutral with respect to ENSO) indicated that when Tdysmc is enhanced over the South Mozambique Channel during JFM, positive rainfall anomalies prevail over large parts of subtropical southern Africa and the Congo Basin with reduced rainfall occuring over most of Madagascar and northern Mozambique. The rainfall differences are associated with enhanced easterly flow towards Madagascar transporting more moisture towards Mozambique and Tanzania, consistent with the increased rainfall. During positive Tdysmc JFM seasons, more tropical cyclones (TCs) were formed in the SWIO and more of them crossed the Mozambique Channel compared to negative Tdysmc seasons. Furthermore, during positive Tdysmc seasons, the landfalling TC was generated in the Mozambique Channel while during the negative Tdysmc ones, it was formed in the central South Indian Ocean. Positive Tdysmc seasons also have increased number of Category5 TCs in the Mozambique Channel. These results suggest that changes in the mixing length temperature, Tdysmc index which can be estimated from satellite data can be useful to monitor and potentially predict regional precipitation as well as the frequency and intensity of tropical cyclones that impact the south-eastern coast of Africa.
15
Achuthavarier, Deepthi. "Role of the Indian and Pacific Oceans in the Indian summer monsoon variability." Fairfax, VA : George Mason University, 2009. http://hdl.handle.net/1920/4524.
Full textAbstract:
Thesis (Ph.D.)--George Mason University, 2009.Vita: p. 179. Thesis director: V. Krishnamurthy. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Climate Dynamics. Title from PDF t.p. (viewed June 10, 2009). Includes bibliographical references (p. 171-178). Also issued in print.
16
Long, Erik Christopher. "An analysis of an eddy-resolving global ocean model in the tropical Indian Ocean." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA241009.
Full textAbstract:
Thesis (M.S. in Meterology and Physical Oceanography)--Naval Postgraduate School, September 1990.Thesis Advisor(s): Semtner, Albert J. Jr. Second Reader: Batteen, Mary L. "September 1990." Description based on title screen as viewed on March 19, 2010. DTIC Descriptors: Climatology, Currents, Cycles, East (Direction), Equations, Equatorial Regions, Global, Heat Flux, Horizontal Orientation, Indian Ocean, Invariance, Mass, Mean, Models, Monsoons, Ocean Currents, Ocean Models, Resolution, Seasonal Variations, Simulation, Surface Temperature, Temperature, Tropical Regions, Velocity, West (Direction), Wind, Wind Stress. DTIC Identifier(s): Leeuwin Current. Author(s) subject terms: Oceanographic Numerical Modeling, Indian Ocean, Ocean General Circulation Model, Eddy-Resolving, Somali Current, Tropical, Equitorial. Includes bibliographical references (p. 137-143). Also available in print.
17
Senan, Retish. "Intraseasonal Variability Of The Equatorial Indian Ocean Circulation." Thesis, Indian Institute Of Science, 2004. http://hdl.handle.net/2005/297.
Full textAbstract:
Climatological winds over the equatorial Indian Ocean (EqlO) are westerly most of the year. Twice a year, in April-May ("spring") and October-December ("fall"), strong, sustained westerly winds generate eastward equatorial jets in the ocean. There are several unresolved issues related to the equatorial jets. They accelerate rapidly to speeds over lms"1 when westerly wind stress increases to about 0.7 dyne cm"2 in spring and fall, but decelerate while the wind stress continues to be westerly; each jet is followed by westward flow in the upper ocean lasting a month or longer.
In addition to the semi-annual cycle, the equatorial winds and currents have strong in-traseasonal fluctuations. Observations show strong 30-60 day variability of zonal flow, and suggest that there might be variability with periods shorter than 20 days in the central EqlO. Observations from moored current meter arrays along 80.5°E south of Sri Lanka showed a distinct 15 day oscillation of equatorial meridional velocity (v) and off-equatorial zonal velocity (u). Recent observations from current meter moorings at the equator in the eastern EqlO show continuous 10-20 day, or biweekly, oscillations of v. The main motivation for the present study is to understand the dynamics of intraseasonal variability in the Indian Ocean that has been documented in the observational literature.
What physical processes are responsible for the peculiar behavior of the equatorial jets? What are the relative roles of wind stress and large scale ocean dynamics? Does intraseasonal variability of wind stress force intraseasonal jets? What is the structure and origin of the biweekly variability? The intraseasonal and longer timescale variability of the equatorial Indian Ocean circulation is studied using an ocean general circulation model (OGCM) and recent in
Abstract ii
situ observations. The OGCM simulations are validated against other available observations. In this thesis, we document the space-time structure of the variability of equatorial Indian Ocean circulation, and attempt to find answers to some of the questions raised above.
The main results are based on OGCM simulations forced by high frequency reanalysis and satellite scatterometer (QuikSCAT) winds. Several model experiments with idealized winds are used to interpret the results of the simulations. In addition to the OGCM simulations, the origin of observed intraseasonal anomalies of sea surface temperature (SST) in the eastern EqlO and Bay of Bengal, and related air-sea interaction, are investigated using validated satellite data.
The main findings of the thesis can be summarized as:
• High frequency accurate winds are required for accurate simulation of equatorial Indian
Ocean currents, which have strong variability on intraseasonal to interannual time scales.
• The variability in the equatorial waveguide is mainly driven by variability of the winds;
there is some intraseasonal variability near the western boundary and in the equatorial
waveguide due to dynamic instability of seasonal "mean" flows.
• The fall equatorial jet is generally stronger and longer lived than the spring jet; the fall
jet is modulated on intraseasonal time scales. Westerly wind bursts can drive strong
intraseasonal equatorial jets in the eastern EqlO during the summer monsoon.
• Eastward equatorial jets create a westward zonal pressure gradient force by raising sea
level, and deepening the thermocline, in the east relative to the west. The zonal pressure
force relaxes via Rossby wave radiation from the eastern boundary.
• The zonal pressure force exerts strong control on the evolution of zonal flow; the decel
eration of the eastward jets, and the subsequent westward flow in the upper ocean in the
presence of westerly wind stress, is due to the zonal pressure force.
• Neither westward currents in the upper ocean nor subsurface eastward flow (the ob
served spring and summer "undercurrent") requires easterly winds; they can be gener
ated by equatorial adjustment due to Kelvin (Rossby) waves generated at the western
(eastern) boundary.
• The biweekly variability in the EqlO is associated with forced mixed Rossby-gravity
(MRG) waves generated by intraseasonal variability of winds. The biweekly MRG wave in has westward and upward phase propagation, zonal wavelength of 3000-4500 km and phase speed of 4 m s"1; it is associated with deep off equatorial upwelling/downwelling.
Intraseasonal SST anomalies are forced mainly by net heat flux anomalies in the central and eastern EqlO; the large northward propagating SST anomalies in summer in the Bay of Bengal are due to net heat flux anomalies associated with the monsoon active-break cycle. Coherent variability in the atmosphere and ocean suggests air-sea interaction.
18
Mellet, Bernice. "Ecological risk assessment of fisheries on sea turtles in the South Western Indian Ocean." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/9957.
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The SWIO is an area of great biodiversity and included in the diverse species that occupy the region are five species of sea turtles that include green turtles, hawksbills, leatherbacks, loggerheads and olive ridleys. Despite considerable conservation efforts at sea turtle rookeries in the South Western Indian Ocean, only green and loggerhead turtle populations have shown an increase in population size in recent years (<10 years), whereas leatherbacks remained stable and hawksbills and olive ridleys declined. This begs the question if fisheries (or other offshore pressures) are responsible for slowing the recovery of these populations in the region, and if so, which specific fisheries are responsible for this trend? Several offshore (mostly industrial) and coastal (mostly artisanal) fisheries overlap with sea turtle distribution at sea. Industrial fisheries that are globally known to have a demonstrable impact on sea turtle populations are longline and to a lesser extent purse seine fisheries, whilst prawn trawl, gillnet and beach seine fisheries are coastal fisheries with a known negative impact on sea turtle populations. Holistic conservation strategies should be developed that include both land and sea protection for sea turtle species. It is thus necessary to identify and manage offshore threats including fisheries activities, particularly those fisheries that are showing the highest risk to sea turtle populations. This prompted an investigation into the bycatch rates and mortality of all sea turtle species that occur in the SWIO region in several offshore and coastal fisheries including both industrial (longline, purse seine and prawn trawl) and artisanal (including gillnet and beach seine) fisheries. The specific aims were (i) to identify and quantify the interactions (and if possible mortality) of sea turtle species in fisheries and (ii) to identify vulnerable species/populations to fishing operations using a semi-quantitative Ecological Risk Assessment (ERA) in the form of a Productivity-Susceptibility Analysis (PSA). Published information, online databases and technical reports were used as data sources to establish a database containing essential information regarding fishing effort and sea turtle bycatch in the region. The existing information was used to map fisheries extent and effort within the region, and to perform bycatch calculations. Interactions and mortality rates for sea turtles in five fisheries were quantified using bycatch rates from regional studies. Between 2000 – 2011, industrial longline and purse seine fisheries captured sea turtles at a rate of 4 388 indiv.y-1, with the mortality rate being 189 indiv.y-1. The bulk of these interactions were in the longline industry that captured 4 129 ± 1 376 indiv.y-1, with a corresponding mortality rate of 167 ± 53 indiv.y-1. The most commonly caught species (in longlines) were loggerheads and leatherback turtles, but the greatest impact is expected to be on the leatherback population due to the high interaction rate relative to population size. The bycatch (259 ± 34 indiv.y-1) and mortality (20 ± 2 indiv.y-1) rates of sea turtles in the purse seine fishery was considerably lower than the longline fishery. The purse seine fishery thus does not seem to have a significant impact on sea turtle populations in the SWIO. The impact of all forms of fish aggregation devices were excluded from the analysis as the impacts of these are poorly documented. Coastal prawn trawl, gillnet and beach seine fisheries captured an estimate of between 50 164 - 52 370 indiv.y-1 from 2000-2011. The highest bycatch rate was estimated for gillnet fisheries (40 264 indiv.y-1) followed by beach seine fisheries (9 171 indiv.y-1) and prawn trawl fisheries (at 1089 – 2795 indiv.y-1). The gillnet fishery could be responsible for slowing the recovery rate of green turtle and leatherback populations in the SWIO due to the high capture rates in this fishery compared to the population sizes of the species. Beach seine and prawn trawl fisheries are not expected to be hamper the recovery rate of any of the populations in the SWIO due to the low levels of interactions and low mortality rates compared to the population sizes. There are however very few data available regarding the bycatch of sea turtle species within these fisheries, highlighting the need for further research regarding this. A productivity-Susceptibility Analysis (PSA) was used to evaluate the relative vulnerability of species to fisheries, and is frequently applied in data poor situations. Limited data on sea turtle life history characteristics and population dynamics of species in the SWIO prompted the use of a PSA to determine the species most vulnerable to fisheries in the region. Results of the PSA indicated that gillnet fisheries poses the largest fishery-related threat to sea turtle populations, specifically the green and leatherback populations. The longline fishery that poses a particular threat to the leatherback population in the SWIO is also a particular concern. A cumulative impact assessment (combining fisheries and other threats) indicated that the SWIO leatherback population is extremely vulnerable to the combination of threats that influence this population in the SWIO. Even though individual fisheries may pose a small threat, the cumulative impacts of the fisheries can lead to severe impacts on populations such as slowing the recovery rate of populations. There are however significant data gaps that require attention in order to fully assess the impact of these fisheries on sea turtle populations. Despite the fact that fisheries are not implicated as a mayor reason for the decline in the hawksbill and olive ridley populations in the region, these two species are in decline indicating that there are other factors responsible for the decline not yet identified. It however remains imperative to reduce the mortality from all sources to ensure the continued viability of sea turtle populations in the region.
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Trampp, David A. "Upper Ocean Characteristics in the Tropical Indian Ocean from AXBT and AXCTD Measurements." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/6882.
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This study focuses on understanding the coupling processes that take place in air-sea interaction during the active and suppressed phases of Madden-Julian Oscillation, and specifically the initiation of MJO. Data used for this study was gathered by a NOAA WP-3D research aircraft under the framework of the Dynamics of the Madden-Julian Oscillation (DYNAMO) research project. The aircraft-based measurements extended from 01 November to 13 December 2011, when 12 research flights were flown in total. A total of 316 AXBT and 114 AXCTD ocean profilers were deployed, yielding 289 AXBT and 106 AXCTD usable profiles that were used for this thesis. For the first time, in situ measurements were made in this region of the world where MJO is initiated. This thesis documents the data quality control and quality assurance efforts for all measured profiles, especially for the AXCTD profiles. It also provides a first look into the large scale variability in the DYNAMO domain and vicinities, and the time variability of the tropical Indian Ocean during the WP-3D operation period. The measurements of the upper ocean reveal enhanced mixing in the active MJO phase and the presence of a warm, stratified, and variable upper ocean in the suppressed phase of MJO. The AXBT/AXCTD measurements also suggest increased mesoscale variability under active convection. Its feedback with the evolution of tropical convection should be investigated in future research.
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Majodina, Mark. "The structure of the upper ocean, atmosphere and heat fluxes - Tropical Indian Ocean." Master's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/18489.
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Sea surface temperatures in the tropical Indian Ocean have been shown to be inversely related to South African summer rainfall, making advanced predictions of this rainfall practicable. Such predictability has enormous potential economic benefits. However, these predictions have been purely statistical; very little is currently known about the marine-atmospheric processes in the Indian Ocean tropics. To address this lack of information, the structure of the upper ocean and lower atmosphere as well as the surface heat fluxes in the tropical Indian Ocean have been investigated. This was done by a special measurement programme on a research cruise in the region. Global gridded meteorological data have been used to complement the shipboard observations. Heat fluxes have been computed from the cruise observations and related to the main atmospheric patterns at the time. These patterns were identified from principal components analysis. Air-sea interaction could thus be estimated over the full tropical Indian Ocean. It is found that the thermocline depth is linked to the cyclonic ocean current shear and to the overlying distribution of wind stress curl. The meridional advection of air into the central Indian Ocean region is shown to modulate the characteristics of the atmospheric boundary layer in the tropical Indian Ocean. The maximum turbulent heat and moisture transports to the atmosphere are found near cyclonic atmospheric disturbances. These are the first reliable observations of the heat and moisture fluxes in that part of the tropical Indian Ocean implicated in South African rainfall. It is clear from this investigation that the synoptic atmospheric systems and the meridional flow of air are critical to enhanced atmospheric convection in the region.
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Good, Jonathan T. "The PLA Navy looks to the Indian Ocean." Thesis, Monterey, California. Naval Postgraduate School, 2002. http://hdl.handle.net/10945/6059.
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Approved for public release, distribution is unlimitedThis thesis examines the implications of China's security needs for the modernization and role of the People's Liberation Army Navy (PLAN). The main argument is that the expansion of China into a new maritime area of operation is likely to solidify Beijing's current regional relationships and possibly lead to a naval arms buildup in the Indian Ocean region. Although the 2001 Quadrennial Defense Review does not explicitly name China, its conclusion that a "military competitor with a formidable resource base will emerge" in Asia clearly implies that the United States will have to take into account China's aspirations to become a regional and potentially global maritime power in the 21st century.
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Holbourn, Ann Elizabeth Lucette. "Lower cretaceous benthic formanifera of the Indian Ocean." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336285.
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Sands, Carla Marie. "Hydrothermal plumes and processes in the Indian Ocean." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/48828/.
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The predicted cycling of the whole ocean through hydrothermal plumes is comparable to the mixing time of the oceans (few thousand years). Hence, understanding hydrothermal plume processes is crucial if their impact on the global geochemical cycles of elements is to be assessed. One of the most important processes that has been demonstrated to modify the gross chemical flux from venting to the oceans is the oxidative precipitation of dissolved Fe (II). It has been hypothesised that this might vary significantly from one ocean basin to another along the path of thermohaline circulation. To test that hypothesis, hydrothermal plume samples were collected from the first confirmed hydrothermal vent fields in the Indian Ocean, at Kairei and Edmond, close to the Rodriguez Triple Junction, during the RRS Charles Darwin cruise CD128 in 2001. The samples were analysed to determine the concentrations of dissolved iron and manganese and particulate Fe, Mn, Al, Ca, Mg, Cu, Zn, P, V, As, Y and the rare earth elements. For a subset of the samples, the concentrations of Fe, Mn, Cu and P in different size fractions of the particulate phase were also measured. Dissolved Fe and Mn concentrations are high in the Kairei and Edmond hydrothermal plumes compared to Atlantic and Pacific hydrothermal plumes previously studied. Particulate Fe concentrations are also high while particulate Mn concentrations remain low throughout the plume. Of the total (i.e. particulate plus dissolved) Fe which emerges from the vents, approximately 20-30% is lost from the plume via the removal of Fesulfide phases formed early in the buoyant plume. Further loss of Fe due to the oxidation and formation of particulate Fe-oxide phases results in a total Fe loss of 50-70%. For the very young non-buoyant plume samples, there is very little in situ particulate Fe present. The behaviour of the chalcophile elements (Cu, Zn, Cd and Pb), elements which exist as oxyanions in seawater (P, V and As), as well as the rare earth elements and Y are consistent with previous studies of elemental behaviours in hydrothermal plumes in the Atlantic and Pacific Oceans. The observed behaviours of these elements with respect to particulate Fe suggests that the differing Fe (II) oxidation rates between ocean basins do not impact the processes taking place within hydrothermal plumes. In addition, fractionation of Fe, Mn, Cu and P in the Edmond hydrothermal plume between the dissolved, colloidal and fine and coarse particulate phases shows consistency with previous conclusions based on only one of these phases. The P/Fe and V/Fe ratios of the hydrothermal particulate samples are intermediate to those of particulate samples from the Atlantic and Pacific Oceans suggesting that as previously hypothesised, these ratios are dependent on dissolved ambient phosphate concentrations. Hence, there remains the potential to use these ratios from sediment cores as paleo-proxies for dissolved phosphate concentrations.
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Wibawa, Teja Arief. "Modélisation globale et régionale de la dynamique de population du thon obèse de l'océan Indien avec le modèle SEAPODYM." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30149/document.
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La pêche au thon indonésienne a souffert d'un problème de gestion dû à des statistiques de pêche incomplètes et peu fiabilité, ce qui entraîne un manque de compréhension de la dynamique des populations de thonidés de la région. Le gouvernement de l'Indonésie a lancé un programme de développement de l'infrastructure pour l'océanographie spatiale (INDESO) afin d'aider à la gestion et au suivi des ressources marines du pays. Une application du projet concerne les pêcheries thonières avec l'objectif ambitieux de modéliser en temps réel et avec des prévisions de quelques jours les distributions et abondances de trois espèces de thonidés: thon obèse, albacore et bonite. Le modèle utilisé est SEAPODYM (modèle spatial d'écosystème et de dynamique de population). La présente thèse traite uniquement du thon obèse et a trois objectifs majeurs: la préparation d'un ensemble de données de pêche géoréférencées, la production de conditions initiales pour la configuration du modèle régional INDESO et la simulation de la dynamique régionale des populations. L'ensemble de données sur les captures et les efforts de pêche géoréférencés du thon obèse de l'océan Indien a été standardisé selon cinq procédures: standardisation de la résolution spatiale, conversion et standardisation des unités de capture et d'effort, recalage des captures géo-référencées au niveau des captures nominales, et détection des principaux changements de capturabilité sur de longues séries temporelles de données sur la pêche.. L'ensemble de données de prises géoréférencées standardisées couvre les deux tiers de la capture nominale totale en raison du manque de références géographiques pour plusieurs flottilles de pêche. Le modèle régional a été configuré en trois étapes: paramétrage du modèle à résolution grossière sur une longue période historique, " downscaling " et paramétrage de la configuration globale opérationnelle et " downscaling " vers le modèle régional opérationnel. La première étape a permis de paramétrer le modèle sur le Pacifique puis l'Océan Indien sur une période de trente-neuf ans à une résolution mensuelle de 2°, permettant d'établir les conditions initiales de la population pour la deuxième configuration, à partir de 1998 et à une résolution hebdomadaire 1/4°. Cette deuxième configuration du modèle a nécessité une méthode de " downscaling " pour réviser le paramétrage et obtenir la même solution malgré quelques différences dans le forçage physique. Ce modèle opérationnel global a ensuite fourni des conditions initiales de la population et des conditions aux frontières ouvertes pour les flux de poissons traversant les frontières régionales du modèle INDESO (1/12 ° de résolution quotidienne). L'ensemble des données de pêche standardisées dans l'océan Indien a été utilisé pour inclure la mortalité par pêche et valider l'optimisation réalisée dans l'océan Pacifique. Les résultats des simulations de modèles suggèrent que le thon obèse est distribué en concentration plus élevée dans l'océan Indien Nord (au nord de 20 °S), avec une extension à travers le canal du Mozambique et le long d'un prolongement vers l'est entre 35 ° et 40 ° S. Les configurations du modèle opérationnel (mondial et régional) utilisent la production primaire nette (VGPM) et la profondeur euphotique dérivées des données satellitaires, ainsi que les cartes mensuelles climatologiques de l'oxygène dissous provenant de l'Atlas Mondial des Océans (WOA) comme forçages biogéochimiques. Une simulation régionale utilisant le modèle INDESO biogéochimique PISCES comme forçage alternatif aux produits dérivés des satellites a été testée. Les résultats préliminaires montrent que, une fois la production primaire PISCES ajustée à la valeur moyenne VGPM, les deux produits donnent des résultats similaires, ce qui suggère que des prévisions à plus long terme basées sur le modèle biogéochimique physique couplé peuvent être proposéesThe Indonesian tuna fishery has suffered from a management problem due to incomplete and less reliability of tuna data leading to lack of understanding about tuna population dynamics in its region. The government of Indonesia initiated the Infrastructure Development of Space Oceanography (INDESO) programme to support marine resource management and monitoring of the Country. One application concerns the tuna fisheries with a challenging objective of real-time and forecast modeling of three tuna species biomass distributions: bigeye, yellowfin and skipjack. The model used is SEAPODYM (Spatial Ecosystem and Population Dynamics Model). The present thesis is dealing with bigeye tuna only, and had three major objectives: the preparation of a geo-referenced fishing dataset, the production of initial conditions for the regional INDESO model configuration, and the simulation of regional population dynamics. The georeferenced fishing catch and effort dataset of the Indian Ocean bigeye tuna was standardized throughout five procedures: standardization of spatial resolution, conversion and standardization of catch and effort units, raising of geo-referenced catch to nominal catch level, screening and correction of outliers, and detection of major catchability changes over long time series of fishing data. . The standardized geo-referenced catch dataset covers two-third of total nominal catch due to lack of geographic references for several fishing fleets. The regional model was configured along three steps: the parameterization of coarse resolution model over a long historical period, the downscaling and parameterization of operational global configuration, and the downscaling to the operational regional model. The first step provided model parameterization over the Pacific and Indian Ocean for thirty-nine years period at 2° monthly resolution, allowing to establish initial conditions of the population for the second configuration starting in 1998 at resolution 1/4° weekly. This second model configuration required a downscaling method to revise the parameterization and achieve the same solution despite some differences in the physical forcing. This global operational model provided initial conditions of the population and open boundary conditions (OBCs) constraining the fluxes of fish through the regional borders of INDESO model (1/12° daily resolution). The standardized Indian Ocean fishing dataset was used for including fishing mortality and validate the optimization achieved in the Pacific Ocean. Model simulation outputs suggest that bigeye is distributed in higher concentration in the North Indian Ocean (north of 20°S), with an extension through the Mozambique Channel and along an eastward prolongation between 35° and 40°S.. The operational model configurations (global and regional) are using VGPM net primary production and euphotic depth derived from satellite data, and climatological dissolved oxygen monthly maps from the World Ocean Atlas (WOA) as biogeochemical forcings. A regional simulation using the INDESO biogeochemical PISCES model forcing as an alternative to the satellite derived products was tested. The preliminary results show that once the PISCES primary production is scaled to the VGPM mean value, both products provide similar results, suggesting that longer time scale forecast based on the coupled physical biogeochemical model can be proposed
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Cobb, Matthew Adam. "Roman trade in the Indian Ocean during the Principate." Thesis, Swansea University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678420.
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Rojsiraphisal, Thaned. "A study of variability in the North Indian Ocean." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273676.
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Karunatilleke, Upali. "The law of the sea and the Indian ocean." Thesis, Southampton Solent University, 2004. http://ssudl.solent.ac.uk/775/.
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Arvid Pardo, the ambassador of Malta presented a revolutionary concept regarding "the sea bed and the ocean floor" when he warned the United States that it must be treated as a "Common heritage of mankind" otherwise it is an area that could lead to conflict between states leading to wars that would spell the end of humanity. The United States took serious note of the underlying potential truth of this warning, sponsored a number of conventions of the Law of the Sea which led to the adoption of UNCLOS III, which was unique in so many respects but the most notable was, it served as a constitution fot the management of the ocean. Two main functions of the sea, namely fisheries and the prevention of pollution, whether land based or vessel sourced, reseived the attention of the world community that participated at the conference that prompted them to adopt a legal framework to establish a conservation and management programme in relation to both subjects. Coastal states were conferred greater jurisdiction, with an expansion of the territorial sea, contiguous sea and a new concept of a 200 nautical mile exclusive economic zone which specified new rights and obligations to all users of the sea, be they coastal states, flag states, port states or any other user. They had to abide these rights and obligations as part of international law. The implementation of these rights and obligations needed the best scientific evidence and knowledge available as well as the cooperation of competent international organisations. It was further envisaged that regional and sub-regional arrangements would be a benevolent method of implementing and monitoring the rights and obligations of states. It was observed that the northern hemisphere states, particularly in the north Atlantic, north Pacific, the North sea, Balkan sea and the Mediterranean sea realized the advantages of regionalism. They brought results such as controlling pollution in the North sea, an area encircled by industrialized states emitting chemical wastes into the sea, with the adoption of harmonized municipal laws. Another significant achievement was the prevention of oil-spills be legislating for double hulling of vessels. The Indian Ocean is surrounded by 28 states, which are categorized as "developing states in the Third world", with the only exception as Australia. These states acquired large resources of the sea with the adoption of UNCLOS III. But they are yet to identify the rights and obligations devolving on them and to realize that if they adhere to the new law, the management of the ocean affairs would ensure sustainable development and contribute to the war against poverty, which is the greatest challenge. This study has identified how these states could, particularly in regard to the prevention of marine pollution and managing living resources, a regional effort could achieve harmonization of laws and make a concerted effort to maintain scientific standard of management and avoid conflict.
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Buchanan, Sarah. "Seismicity and tectonics of the Central Indian Ocean Basin." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/13246.
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The central Indian Ocean exhibits a higher level of earthquake activity than is normally associated with a region distant from conventional plate boundaries. This anomalous seismicity has been the subject of previous studies which assigned large focal depths (as deep as 40km below the seafloor), despite crustal faulting and folding observed on seismic reflection profiles. I re-examine the distribution and source parameters of teleseismically recorded earthquakes and relate them to the tectonic setting of the Central Indian Ocean Basin. Previous studies have used long-period waveform modelling, which gives unreliable focal mechanisms for small earthquakes (mb <5.5), and poor resolution of depth for shallow earthquakes (<100km). Zero-phase broad-band conversions from short period and broadband waveforms are used with a detailed velocity structure derived from seismic reflection data obtained by the Marion Dufresne in the Central Indian Basin, to assign the more accurate focal depths (±3km). Measurements of the relative amplitudes of P arrivals, and surface reflections from the seafloor and sea surface, are used to constrain fault plane solutions even when P-wave first motion polarities cannot be determined. Unlike in other oceanic intraplate settings, the seafloor reflection is small and unclear, due to high sediment deposition in the Bengal Fan. The earthquakes have either thrust or strike-slip mechanisms and their depths are in agreement with previous studies, with no depths shallower than 22km below the seafloor in the Central Indian Ocean Basin or Wharton Basin. Earthquakes in the Bay of Bengal are shallower, possibly due to loading by Fan sediments raising lithospheric stresses beyond failure. The directions of the compressional axes of the earthquakes are in agreement with those predicted by plate models. The seismicity shows a concentration between the Afanasy Nikitin Seamount and the Ninety East Ridge. Other earthquakes are evenly distributed between 10°N and 10°S, and 80°E and 95°E. The existence of an aseismic region west of 80°E suggests that there are low strain rates in the west Central Indian Ocean Basin, associated with the proximity of the proposed Euler pole of rotation between separate Indian and Australian plates.
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Manyilizu, Majuto Clement. "Simulation of variability in the tropical Western Indian Ocean." Doctoral thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9310.
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Includes bibliographical references.The oceanic circulation and properties in the Tanzanian shelf region in the tropical western Indian Ocean have been studied in this thesis using a regional ocean model. The study investigated the influences of the Northeast Madagascar Current (NEMC) in the Tanzanian shelf waters at the annual cycle. Furthermore, the thesis examined the interannual variability of the sea surface temperature (SST) in the Tanzanian shelf region, and compares it with that offshore or with subsurface temperature. At the annual cycle, the westward-flowing NEMC advects relatively warm and fresh waters from the north of Madagascar towards the Tanzanian shelf region by interrupting the upwelled water from the Seychelles-Chagos ridge. At interannual timescales, the weakest interannual SST variations, which lie over the weak subsurface waters variations, occur in the coastal waters off Tanzania, where its variance is shared with waters to the north of Madagascar. Such SST variations are dominated by variability at about five year periods. The strongest interannual SST variations, which lie over the strongest subsurface temperature variations, occur offshore, being dominated by two periods, one at about 2.7 and the other near five years. The interannual variability of the region seems to be linked to El Niño- Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events, which induce changes in the thermocline and surface forcing in the region. Local surface heat flux exchanges driven by the anomalous shortwave radiation dominate the weakest interannual SST variability in the Tanzanian shelf region, with some contribution by the advection of heat anomalies from the NEMC. Further offshore, the strongest interannual variability of the SST is dominated by the thermocline variations induced by local Ekman pumping from local wind stress curl and by remote forcing from large-scale climate modes.|
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Steele, Nikita. "Geographical variation in effects of nutrient levels and grazing intensity on community structure between upwelling and non-upwelling regions of South Africa." Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1013013.
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The aim of this thesis was to assess the influence of upwelling on alga-grazer interactions in rocky shore communities along the south coast of South Africa using grazer exclusion treatments with controls and procedural controls set out in a block design and monitored for algal cover roughly monthly for one year. In the first experiment grazers were excluded from treatment plots at two upwelling and two non-upwelling sites and the rates of algal biomass accumulation were then compared. The upwelling sites showed significantly faster algal colonisation rates, with Ulva rigida being the first species to colonise the rocks. Final algal cover and biomass did not differ significantly between upwelling and non-upwelling sites in control plots open to grazers, but were significantly higher in grazer exclusion plots at upwelling sites indicating stronger grazing effects. This was confirmed by estimating the intensity of grazing using the log-response ratio (LRR), which was calculated from treatment and control plots. Upwelling sites had significantly lower LLR values indicating stronger grazing effects, than at non-upwelling sites, despite no difference in grazer abundances. The second experiment examined the effects of nutrient addition on algal growth and community composition by comparing high nutrient enrichment plots with low enrichment plots at one upwelling and one non-upwelling site. ANOVA indicated faster growth rates and significantly higher final algal biomass in high enrichment plots compared to low enrichment and control plots at both upwelling and non-upwelling sites. A two-way ANOVA indicated significantly higher algal cover in high enrichment plots compared to the data from the grazer exclusion plots in experiment 1 at both sites, suggesting that nutrient addition plays a major role in algal growth and community composition. The findings of these studies have shown significant differences between treatments, sites and seasons, with significant differences not only occurring in algal cover but also accumulation of algal biomass and recruitment patterns between treatments. The small scale local processes acting within a few centimetres (plots) or tens of meters (among blocks) can also be reflected over larger scales such as sites (upwelling/non-upwelling shores). Further, these studies have demonstrated that various factors such as the effects from increased nutrients at upwelling cells and the change in grazing effects due to enhanced nutrients can determine the abundance and diversity of the community structure, including an increase in the abundance of the fast growing algae Ulva rigida, and a slow recovery of the brown and red algae.
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Cowburn, Benjamin. "Coral reefs and climate change in the Indian ocean : a case study of Watamu Marine National Park, Kenya and other Indian Ocean locations." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:22c16252-bdf9-4724-a2f8-dbd4c6fe7f09.
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Coral reefs are arguably the most threatened marine habitat because of multiple anthropogenic stressors degrading the health and resilience of these systems. In the past 20 years there have been increasing observations of mass coral bleaching and mortality associated with increasing water temperatures in the tropics. Reefs provide ecosystem services worth billions of dollars to people living in tropical coastal areas and are the architects of one of the most beautiful structures found on earth. Conserving these habitats is paramount, and conservation planning must contend with climate change along with local and regional stressors. In this thesis Watamu Marine National Park in Kenya is used as a case study of the current challenges facing the conservation of reefs in a warming world. The Western Indian Ocean suffered dramatic bleaching during 1998, which caused the mortality of 70% of Watamu's corals. Using datasets from the 1980s to present the historical trajectory of Watamu's reef community is presented. The current ecosystem resilience is assessed to suggest how this reef will respond to future climate stress. It appears that Watamu's coral community has remained in an altered state post-1998, which, based on its past thermal stress and current coral community, should be resistant to future bleaching. Watamu's resilience and reef health is compared with other locations in the Indian Ocean, including reefs in Kenya and the Maldives that bleached in 1998 and examples from Mozambique and Sumatra of reefs with little evidence of historical thermal stress. Resilience is a multi-faceted process with different major components and numerous interacting factors, which act synergistically on the reef community. Conservation options and opportunities are discussed for the 6 locations examined, using current resilience models and theory as a framework for identifying priority actions. Local and regional-scale human impacts on shallow marine habitats during the last 50 years has been dramatic, and with global-scale climate change as an additional major threat, the next 50 years will be critical for the future of reefs. The locations visited during this study showed encouraging signs of resilience to past thermal stress, with evidence to suggest that corals are acclimatising and/or adapting to increasing water temperatures. The future of reefs in locations like Watamu is uncertain. Better understanding of reef ecology, appropriate conservation techniques and ultimately greater public concern for reefs is required to ensure that there is a future for these ecosystems in the Indian Ocean.
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Hagan, Annelise Baugh. "Reef regeneration at Alphonse Atoll, western Indian Ocean following the 1997-98 ocean warming event." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599825.
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Following the 1997-98 ocean warming event, extensive coral bleaching and mortality occurred world-wide. Alphonse Atoll in the Southern Seychelles (7°1’S; 52°44’E) is a suitable site for the investigation of reef recovery after bleaching due to its manageable size (11.28 km2) and its geographical isolation, making it a natural laboratory unaffected by anthropogenic impacts. One year after the bleaching event, scleractinian cover had greatly reduced (10% cover) but macroalgal cover had increased (up to 27% cover). This high level of macroalgae did not persist, and over time, scleractinian cover increased, reaching a maximum of 23% cover by 2003. Despite the increased percentage scleractinian cover 1998-2003, there was no associated increase in coral diversity, with much of the increase being attributed to colonisation by opportunist species of Pocillopora and Acropora spp. Coverage of calcareous algae increased greatly following the bleaching event, from a maximum of 10% cover in 1998 to 40% cover in 2003. Rubble comprised one third of the benthos in 1998 and remained at this level throughout the 5 year monitoring period. Depth and aspect significantly influenced the benthic communities. A ‘phase shift’ from a ‘hard’ reef community to a ‘soft’ reef community, reported elsewhere, has not occurred at Alphonse but an altered coral community exists in the post-bleaching period. Large skeletons (1-3 m diameter) of Porites spp., Lobophyllia spp., colonised by Pocillopora spp. and to a lesser extent Acropora spp., suggest that the Alphonse fore-reef slope may be in an interim phase of development, through which the coral community must pass before regaining the high levels of coral coverage and diversity. Recruitment patterns, from local refugia versus long-distance dispersal, are discussed.
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Chen, Shuiming. "Vertical structure of mesoscale ocean currents in the Indian Ocean observation, numerical modeling and theory /." Thesis, University of Hawaii at Manoa, 2003. http://proquest.umi.com/pqdweb?index=0&did=765960941&SrchMode=2&sid=8&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1209408688&clientId=23440.
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Layton, Simon. "Commerce, authority and piracy in the Indian Ocean world, c. 1780-1850." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608198.
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Meuleners, Michael Joseph. "A numerical study of the mesoscale eddy dynamics of the Leeuwin Current system." University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0134.
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[Truncated abstract] The study of eastern ocean boundary currents has been principally restricted to the Pacific and Atlantic ocean regions. The traditional view of the circulation near eastern ocean boundaries is that upwelling-favourable winds force surface waters offshore, leading to upwelling of cold, nutrient-rich subsurface water at the coast, the formation and offshore advection of a coastal front, and the generation of alongshore currents, generally having an equatorward surface flow and a poleward undercurrent. The eastern ocean boundary system of the southern Indian Ocean, off the west coast of Australia, is unique compared with these regions because a warm, poleward surface flow, known as the Leeuwin Current, dominates the dynamics over the continental shelf. Satellite imagery has shown the Leeuwin Current consists of a complex system of meanders, jet-like streams, and eddies, and has a seasonal and interannual variability. The oceanic circulation of the region between Carnarvon (latitude 25°S) and Jurien Bay (latitude 31°S) was examined using observational and remotely sensed data in conjunction with a detailed numerical modelling study. The model was validated using in situ ADCP and CTD data, and the horizontal eddy viscosity parameterization was tested against field observations. ... The resulting offshore meander grew laterally, shallowed, and closed to form an anticlockwise eddy to the original clockwise eddy’s south, forming a characteristic LC eddy pair (dipole). The model demonstrated the LC and Leeuwin Undercurrent (LUC) coupling played an important role in the onset of eddies at both sites. When an energy diagnostic scheme was used, the dominant instability process linked to the anticlockwise eddy’s development at site 1 was a mixed mode barotropic and baroclinic instability. The baroclinic instability’s source was the available potential energy stored within the mean lateral density gradient. The LC’s meandering southerly flow interacting with the LUC’s northerly subsurface flow generated the horizontal shear that sourced the barotropic instability. The dominant instability process at site 2 was baroclinic in origin. Possible links between the eddy field dynamics and the shelfslope region’s alongshore topographic variability were considered. The results of a suite of five model runs, differing only in the specification of bottom topography, were contrasted to investigate the effects. Except for the expected alongshore variability, delay in the onset of instabilities, varying growth rates, and some differences in the dominant wavebands’ mesoscale patterns, the overall impression was the response was similar.
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Johnson, Gregory Conrad. "Near-equatorial deep circulation in the Indian and Pacific Oceans /." Thesis, Woods Hole, Mass. : Woods Hole Oceanographic Institution, 1990. http://hdl.handle.net/1912/2637.
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Thesis (Ph. D.)--Woods Hole Oceanographic Institution and Massachusetts Institute of Technology, 1990.Funding was provided by the Office of Naval Research and a Secretary of the Navy Graduate Fellowship in Oceanography. References : p. 117-121.
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Bader, Jürgen. "The role of the tropical Indian Ocean in global climate." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974330051.
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Cirano, Mauro School of Mathematics UNSW. "Wintertime Circulation within the Southeast Indian Ocean: a Numerical Study." Awarded by:University of New South Wales. School of Mathematics, 2000. http://handle.unsw.edu.au/1959.4/17820.
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A numerical study is made of the wintertime circulation within the Southeast Indian Ocean (SEIO). The downwelling favourable winds result in a continuous eastward Coastal Current (CC) extending from Cape Leeuwin to the eastern coast of Tasmania, where it forms a confluence with the south branch of the East Australian Current. An additional forcing mechanism for the CC is the Leeuwin Current in the western part of the domain. The study here is divided in two parts: (1) available data and the wintertime averaged results from the Ocean Circulation and Climate Advanced Model (OCCAM) are analysed to provide a first order description of the large-scale circulation; (2) a high resolution model (Princeton Ocean Model) is nested within OCCAM to examine the shelf-slope circulation within the eastern SEIO. The nested model is forced with climatological monthly average winds and several experiments were run to simulate the effects of surface fluxes of density, enhanced bottom friction and stronger winds. In summary, the shelf-slope circulation is governed by a surface south-eastward CC that carries around 2 Sv and reaches velocities of up to 50 cm/s, where the shelf is narrowest. The core of the current is generally constrained to the shelf-break region. Zonal winds and geostrophic control of the CC lead to a transport of 1 Sv through Bass Strait and a north-eastward jet that is directed into the strait between King Is. and Tasmania. Further south, the CC is poleward and known as the Zeehan Current (ZC). Between Cape Leeuwin and Tasmania and over the slope region, a westward current (the Flinders Current) is found at depths of 500-1000 m and has an associated transport of 5-7 Sv. The current is shown to result from a northward Sverdrup transport in the deep ocean. Meso-scale eddies are shown to result from baroclinic instability and have wavelengths of around 250 km and transports of 3-4 Sv, and can dominate the slope circulation. A comparison of the numerical results is also made with two current meter data sets and results show an interannual variability in the ZC strength, that is probably related to ENSO.
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Bertram, Caroline Jane. "Rare earth elements and neodymium isotopes in the Indian Ocean." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277641.
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Bull, Jonathan Mark. "The structural style of intraplate deformation, central Indian Ocean Basin." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/15535.
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The intraplate deformation in the Central Indian Ocean Basin is a well known example of a deviation from an axiom of plate tectonics: that of rigid plates with deformation concentrated at plate boundaries. In this thesis a range of geophysical data collected during CHARLES DARWIN Cruise 28, together with several different geodynamic modelling techniques, is used to investigate the structural style of intraplate deformation. The deformation occurs in lithosphere of age 65-90 Ma that formed at a fast spreading-rate (im60 mm yr-1) at the south-east Indian Ridge. It manifests itself as a diffuse zone of compressional and strike-slip earthquakes, high localised heat-flow, geoid anomalies and tectonic deformation. The tectonic deformation can be considered to be occurring on two spatial scales: the first order is represented by long wavelength (100-300 km), large amplitude (1-2 km) undulations of oceanic basement and overlying sediments; and the second order by unusual high-angle reverse faults with associated folds in the basement cover. The reduction and inversion of disposable sonobuoy data revealed that the velocity-depth structure of the oceanic crust is not unusual. The sediment velocity increases from 1.6-1.7 km s-1 in the near surface to 3.4-3.5 km s-1 immediately above basement with a velocity gradient of 0.75 s-1. A velocity for the top of the oceanic layer 2 of 4.1 km s-1 was identified as layer 2A. An estimate for the thickness of the crust could not be made from the sonobuoys and other refraction work is contradictory. A study of structural style from single-channel seismic reflection profiles revealed that the reverse fault fabric, which has a strike (0900-100oE) perpendicular to that of fracture zones (005o-010oE) developed in this area, resulted from the reactivation under compression of two sets of spreading-centre formed normal faults. In the survey area the first and second orders of deformation are discontinuous across fracture zones. A transpressive model is developed for the survey area to explain the discontinuity of the axes of the undulations, other basement trends, and regional seismicity studies. Previously, two hypotheses had been advanced for the formation of the long wavelength undulations: buckling and inverse boudinage of the lithosphere. This study used three modelling techniques to determine the deformation mode, two of which decisively favoured buckling. Physical modelling using the sandbox technique, in which the oceanic lithosphere was modelled with a two layer (brittle/viscous) rheology, suggested that buckling of the entire brittle lithosphere was responsible for the formation of the long wavelength undulations. Two and three-dimensional gravity modelling supports buckling of at least the oceanic crust. However, numerical modelling was unsuccessful in modelling the long wavelength undulations. The transpressive model for the Central Indian Ocean Basin, on which buckling forms within fracture zone compartments, and strike-slip motion occurs both along fracture zones (left-lateral) and along the reactivated ridge-parallel fabric, may be extended eastwards to the Wharton Basin. Compressive forces with anticlockwise rotation are seen as a consequence of a dramatic change in plate boundary activity in the north-eastern Indian Ocean from 7 Ma ago, with subduction occurring faster at the Sunda Trench than continental collision at the Himalayas.
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Mitchell, Kimbriel Armistead. "American strategic policy for the Indian Ocean area, 1970-1980." Thesis, London School of Economics and Political Science (University of London), 1991. http://etheses.lse.ac.uk/1149/.
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This thesis analyzes America's strategic policy for the Indian Ocean area from 1970 to 1980 and assesses the efficacy of its contribution to the US security objectives there of upholding friendly, primarily Persian Gulf states' security and stability, maintaining access to oil, ensuring the safety of shipping and limiting Soviet influence. Minor intermittent naval display succeeded in balancing the Soviet naval presence, the main purpose of American policy until 1979, because that presence was too small to exercise significant influence. The littoral states, however, were ambivalent: they wanted the US to balance the USSR but feared a potential super-power naval arms race. Naval display failed as part of America's indirect threat in 1973-74 to retaliate against friendly Gulf Arab states if they continued the oil embargo caused by the October 1973 Middle East war. America modified its strategic policy when Gulf security became more precarious after the Iranian revolution in early 1979. It intensified its naval display and began to approximate a land force presence in South-West Asia in order to show greater concern for its interests, to reassure friends about its reliability as a security actor and to enhance the political and military balance against the Soviets. The US emphasized more direct and active deterrence against a potential Soviet or Iraqi attack and preparation for intervention, if necessary, within a friendly Gulf state in order to protect access to oil. America's modified policy gave some reassurance to friendly Gulf states that shipping would be safe, that, available in the background and if requested in a crisis, its armed forces would help them to cope with likely external threats and that the US was more determined to counter the USSR. But America was also perceived to be a political and potential interventionist danger to friendly countries and to be of uncertain reliability in the event of "worst case" Soviet or Iraqi aggression because its immediately available combat capability was weak. The US armed forces were unnecessary and virtually inappropriate for helping friendly regimes to maintain domestic stability or for preserving access to oil. America's strategic policy was of little relevance for limiting the USSR's improvement of its political and strategic position in South-West Asia in the late 1970s, and more direct and active US deterrence reinforced marginally at most the Soviet intention not to attack into the Persian Gulf.
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Huussen, Tycho Nout. "Is the Indian Ocean MOC driven by internal wave breaking?" Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/209663/.
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This dissertation investigates the energetics of the Indian Ocean Meridional Overturning Circulation (MOC) using hydrographic data (Part I), and the interaction between a broad band internal wave field and a mean flow using idealized numerical simulations (Part II). The main objective of this work is to quantify how much energy is needed to drive the Indian Ocean MOC and to compare this with the energy available in the internal wave field. The turbulent dissipation needed to sustain the MOC is estimated by assuming a `mixing efficiency' of 0.2 and an advective-diffusive balance in neutral density layers. The advective transport of mass into this box-model is based on published estimates of the flow field at 32�S and the Indonesian Through-flow. A comparison of the large scale dissipation rates with estimates of the input of energy by the tides and the wind shows that most published overturning solutions require more energy than is likely to be available. This result suggests that energy budgets may be useful as constraints in inverse models. Estimates of turbulent dissipation due to internal wave breaking are inferred from in-situ observations of shear and strain using a fine scale parameterization. The isoneutral mean of the inferred internal wave dissipation rates is about one order of magnitude smaller than dissipation rates inferred from the large scale flow fields. This result appears robust when considering potential sampling biases in the internal wave observations and leads to the main conclusion of this work: the Indian Ocean MOC cannot primarily be driven by internal wave breaking. A preliminary investigation into other processes capable of dissipating energy in the ocean interior shows that the MOC may be closed by hydraulic turbulence in the numerous Fracture Zones in the Indian Ocean.
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Motah, Beenesh Anand. "Environmental influences on tuna movement patterns in the Indian Ocean." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/24518.
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The Indian Ocean Tuna Commission conducted a small-scale tagging programme (2002-2009) and also a large-scale tagging programme: the Regional Tuna Tagging Programme of the Indian Ocean (RTTP-IO, 2005-2009). Both tagging programmes known as the Indian Ocean Tuna Tagging Project (IOTTP), targeted three main species of tuna commercially exploited in the Indian Ocean: bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis) and yellowfin (Thunnus albacares). The two programmes tagged 219,149 tuna and 34,294 recaptures were reported to the commission. This study focused on tuna behaviour in the Indian Ocean looking at seasonal impacts, inter-annual variability in relation to ocean environment, survival estimates, movement patterns, size-groups and school-type: Free Schools (FS) and Fish Aggregating Devices (FADs). Using a multivariate approach, it was found that the years 2005 to 2007 were most abundant in recoveries of skipjack adults (77.45%) while yellowfin adults were mainly abundant during 2008 to 2011. It also showed that year and zone were significant factors influencing local abundance in tuna. The Kaplan-Meier survival curves enabled estimates on the longevity of the three species to be made. It was estimated that the cohorts (99%) vanished at 12, 5.8 and 10 years for bigeye, skipjack and yellowfin, respectively. The years 2006 (cold-productive phase) and 2007 (warmchlorophyll depleted phase) showed tuna movement patterns changing with an El Ni˜no event and primary productivity. Tuna tagged in the Tanzanian region, showed that those under FADs moved pre-dominantly towards the Somalian and Seychelles waters, while those in FS moved to the Seychelles and Mozambique waters. General Additive Model (GAM) analyses showed that the area bounded by 5⁰N-5⁰S and 45⁰-55⁰E was the main tag recovery regions for tuna under FADs. While in FS, the core recovery region was observed to be from 0⁰N-10⁰S and 50⁰-60⁰E. Recoveries were distributed in the temperature range 25-29 ⁰C. Modelling tuna movement and drift related to ocean surface currents and swimming speed, a closer match between simulated and actual recovery positions were obtained for large tuna (particularly free schools) in comparison to small tuna associated with FADs.
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Parker, Bhawoodien Abbasmia. "Composite structure of tropical cyclones in the SW Indian Ocean." Master's thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/19524.
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This work examines SW Indian Ocean tropical cyclone (TC) structure as a function of movement using ECMWF gridded data. Analyses of the mean summer climate for the period 1987 1992 shown that conditions conducive to the development ofTCs are present between the latitudes 5° and 15°S. Six westward moving TCs are selected to form the westward moving composite TC and four are used in the recurving TC composite from 3-days before the maximum surface intensity to 1 day after. The westward moving composite was found to have a steady TC signature. Comparisons were made with TC Firinga which passed near Mauritius on 29 January 1989. The recurving TC composite was found to exhibit rapid growth with sharp parameters tendencies. Interaction with a sub tropical trough is seen in both TC composites. Upper level westerly winds create effective uplift which strengthens the recurving TC on the poleward side. Spectral analysis of a rainfall index compiled from Mauritius data demonstrates spectral peaks at the seasonal and intra-seasonal scale. Three peaks were identified. one within the 40-60 day Madden Julian Oscillation. one at 23 days and one with a 16 day oscillation. The 23 day oscillation was found to have a highest spectral power. The results of TC and rainfall analyses offer useful insights to the climate and weather of the SW Indian Ocean.
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Hughes, Lindsay. "A Rising Tide: The Growing Nuclearisation of the Indian Ocean." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/86667.
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"This dissertation examines why the Indian Ocean is becoming, increasingly, the locus of nuclear weapons and platforms.
It establishes a nexus between Realism, the desire of states to maximise their power, the role of nuclear weapons in that quest, Seapower, and the importance of the Indian Ocean to the US, China, Pakistan and India.
It demonstrates that the Indian Ocean is becoming nuclearised because of the confluence of its growing strategic importance and that nexus."
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Day, John Frederick. "British Admiralty control and naval power in the Indian Ocean (1793-1815)." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3919.
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This thesis aims to explain how British naval power was sustained in the Indian Ocean during the French Revolutionary and Napoleonic Wars. To improve efficiency and economy, the Admiralty had to reorganise the management of shore support services, as well as to rationalise the bases available to the navy to meet the enemy it faced. The basic proposal of this thesis is that British naval power was projected overseas by the Admiralty's effective reconciliation of two competing demands, the naval demand for strategic deployment and the domestic demand for reform. The thesis argues that British naval power in the Indian Ocean was increased by the acquisition of the Cape of Good Hope and Trincomalee and the naval bases built at these locations. The removal of the navy from complete dependence on the East India Company for support services was part of a long term policy of increasing Admiralty control of facilities in the east. In 1793 Bombay was the main naval base but Madras quickly became another hub supporting naval activities in the east. Other locations were considered. Calcutta was used and investigations were made into developing Penang as a navy base before Trincomalee became part of Britain’s long-term naval infrastructure. At the Cape a separate naval command was given responsibility for part of the Indian Ocean. Following the capture of Mauritius in 1810 this island was used temporarily as a forward support base. Admiralty control of the naval support services delivered to the squadrons at the Cape and in the East Indies was dramatically improved by the appointment overseas of resident commissioners from 1809. This resulted from the implementation of the recommendations of the Commission of Naval Revision, first suggested by the Commissioners on Fees in 1788. Resident commissioners ensured Admiralty instructions and policies were implemented and executed, resulting in improved efficiency and reduced costs.
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Zientek, James B. "China and India the struggle for regional maritime supremacy in the Asia-Pacific and Indian Ocean /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA387367.
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Thesis (M.A. in National Security Affairs) Naval Postgraduate School, Dec. 2000.Thesis advisor(s): Miller, H. Lyman. "December 2000." Includes bibliographical references (p. 127-134). Also available online.
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Hanson, Christine Elizabeth. "Oceanographic forcing of phytoplankton dynamics in the coastal eastern Indian Ocean." University of Western Australia. Centre for Water Research, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0033.
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[Truncated abstract] This work was the first large-scale biological oceanographic study to be undertaken in the coastal eastern Indian Ocean adjacent to Western Australia, and covered both northwest (Exmouth Peninsula to the Abrolhos Islands) and southwest (Cape Naturaliste to Cape Leeuwin) regions. The study area was dominated by the Leeuwin Current (LC), an anomalous eastern boundary current that transports tropical water poleward and prevents deep nutrients from reaching the surface by creating large-scale downwelling. Indeed, LC and offshore waters were consistently associated with low nitrate concentrations and low phytoplankton biomass and production (< 200 mg C m-2 d-1). However, the physical forcing of the LC was offset, during the summer months, by upwelling associated with wind-driven inshore countercurrents (Ningaloo and Capes Currents), which provided a mechanism to access high nutrient concentrations normally confined to the base of the LC. ... Limited seasonal investigations off the Capes region of southwestern Australia showed that the winter production scenario can be very different than summer conditions, with strong Leeuwin Current flow that meanders onto the continental shelf and entrains seasonally nutrient-enriched shelf waters. However, production in the LC was still low (≤450 mg C m-2 d-1) due to light limitation resulting from both increased light attenuation and reduced surface irradiance characteristic of the winter months. This investigation provides fundamental knowledge on physical-biological coupling off Western Australia, with implications for fisheries management in view of seasonal and inter-annual variability in the strength of both the Leeuwin Current and inshore countercurrents.
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Meilland, Julie. "Rôle des foraminifères planctoniques dans le cycle du carbone marin des hautes latitudes (Océan Indien Austral)." Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0059/document.
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Les foraminifères planctoniques vivants (LPF) contribuent à la pompe biologique du carbone océanique en générant des flux de Corg (cytoplasme) et de Cinorg (test calcaire). Dans cette étude, la morphométrie des tests, les abondances et les compositions spécifiques des assemblages de LPF dans l'océan Indien Sud (30°S-60°S, 50°E-80°E), ont été caractérisées à partir de la collecte par filet à plancton stratifié (Multinet) sur 19 stations échantillonnées pendant trois étés consécutifs (2012- 2014). En démontrant l'efficacité d'échantillonnage du Continuous Plankton Recorder pour spatialiser les données observées en 19 stations, l’étude de la dynamique de population des LPF montre l'effet de la position des fronts sur la production des LPF. Pour mieux contraindre l'impact des LPF dans la pompe biologique du carbone des hautes latitudes, la biomasse protéique et la masse calcique de plus de 2000 foraminifères ont été mesurées. Les différences de biomasse protéique et de poids normalisé par la taille entre années, espèces et masses d'eau suggèrent que les paramètres environnementaux affectent la production de Corg et de Cinorg des LPF. Le rôle des LPF sur la pompe biologique de carbone marin dépend des conditions hydrologiques et trophiques du milieu. Le rapport Corg/Cinorg est très différent selon les espèces considérées. L'applicabilité des tests de foraminifères planctoniques comme proxy de paléopompe du carbone dans les hautes latitudes dépendrait donc de l'effet exercé par les variations des conditions écologiques, et de la composition de l’assemblage. Cette étude propose une première estimation des budgets Corg et Cinorg produits par les LPF dans l’Océan Indien AustralPlanktonic foraminifera contribute to the marine biological carbon pump by generating organic (cytoplasm) and inorganic (shell) carbon fluxes. In this study, we characterized LPF total abundances, assemblages and test morphometry (minimum diameter) along 19 stations sampled by stratified plankton net (Multinet), during three consecutive austral summers (2012-2014) in the Southern Indian Ocean (30°S-60°S, 50°E-80°E). By demonstrating the efficiency of CPR for LPF sampling, we analysed population dynamic between 19 multinet sampling stations, showing the effect of frontal position on LPF production. To better constrain the impact of those organisms in the biological carbon pump at high latitudes, we have quantified the individual protein-biomass and test calcite mass of more than 2000 LPF. Differences in size-normalized protein-biomass and in size-normalized weight between years, species, and water bodies suggest that environmental parameters affect the production of planktonic foraminifera organic and inorganic carbon to varying degrees. Consequently, planktonic foraminifera are assumed to affect the biological carbon pump, depending on ecological conditions and biological prerequisites. The applicability of planktonic foraminifera tests as proxy of the past biological carbon pump in high latitudes would hence critically depend on the effect exerted by changing in ecological conditions, and the presence of different species. This study proposes a first estimation of planktonic foraminifera Corg and Cinorg standing stock and fluxes in the Southern Indian Ocean
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Lee, Jong-Mi Ph D. Massachusetts Institute of Technology. "Evolution of Anthropogenic Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82318.
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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), 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
Pb and Pb isotopes in the ocean have varied on decadal to centennial time scales due to anthropogenic Pb inputs. Thus, tracing the temporal variation of Pb and Pb isotopes in the ocean provides information on the major sources of Pb and the transport of Pb from sources to the ocean surface and into the ocean interior. In this thesis study, first, a method was developed for the analysis of dissolved Pb and other trace elements in seawater using single batch nitrilotriacetate resin extraction and isotope dilution ICP-MS, which was applied in analyzing seawater Pb concentrations in the rest of the study. A -550 year history of the Pb and Pb isotopes in the deep North Atlantic Ocean is reconstructed using a deep-sea coral, showing the infiltration of anthropogenic Pb to deep sea. Comparing the results to the surface North Atlantic Ocean Pb record using a Transit Time Distribution model, the mean transit time of Pb is estimated to be -64 years. This is longer than the transit time estimate assuming simple advection from a source, showing the importance of advective-diffusive mixing in the transport of Pb to the ocean interior. The later part of the thesis investigates Pb in the Indian Ocean, where no useful Pb data have been previously reported. First, using annually-banded surface growing corals, I reconstruct variations of Pb and isotopes in the surface waters of the central and eastern Indian Oceans during the past half-century. Results of the study show the increase of Pb concentrations from the mid-1970s, and major sources of the Pb are discussed, including leaded gasoline and coal burning, based on their emission histories and Pb isotope signatures. Second, Pb concentration and isotope profiles are presented from the northern and western Indian Oceans. Higher Pb concentrations and lower Pb isotope ratios (206Pb/ 207Pb, 208Pb/207Pb) are found in the upper water column (by Jong-Mi Lee.
Ph.D.