Dissertations / Theses on the topic 'Antarctic Ocean and Antarctica'
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Scolardi, Kerri M. "Distribution, Metabolism and Trophic Ecology of the Antarctic Cydippid Ctenophore, Callianira antarctica, West of the Antarctic Peninsula." Scholar Commons, 2004. https://scholarcommons.usf.edu/etd/1240.
Full textGoddard, Paul B., Carolina O. Dufour, Jianjun Yin, Stephen M. Griffies, and Michael Winton. "CO2-Induced Ocean Warming of the Antarctic Continental Shelf in an Eddying Global Climate Model." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626296.
Full textBoehme, Lars. "The frontal system of the Antarctic Circumpolar Current : marine mammals as ocean explorers." Thesis, St Andrews, 2008. http://hdl.handle.net/10023/687.
Full textWilliams, Adam Peter. "Antarctic climate : ocean fluxes and variability." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/63753/.
Full textLange, Louise. "Feeding dynamics and distribution of the hyperiid amphipod, Themisto gaudichaudii (Guérin, 1828) in the polar frontal zone, Southern Ocean." Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005382.
Full textDaly, Ryan. "Trophodynamics of mesozooplankton in the the vicinity of the subtropical convergence in the Indian sector of the Southern Ocean." Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1005479.
Full textGrigorov, Ivo. "Southern Ocean palaeoceanography from Thalassiothrix antarctica deposits." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413434.
Full textSheen, Katy Louise. "Seismic oceanography : imaging the antarctic circumpolar current." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609132.
Full textOmbres, Erica H. "Gradients in Season, Latitude, and Sea Ice: Their Effect on Metabolism and Stable Isotopic Composition of Antarctic Micronekton." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4554.
Full textZanowski, Hannah Marietta. "The Influence of Antarctic Open-Ocean Polynyas on the Abyssal Ocean." Thesis, Princeton University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10248291.
Full textIn the mid-1970s, an enormous open-ocean polynya developed in the Weddell Sea. Since the Weddell Polynya's occurrence, no polynya of similar size or duration has been observed in the region. A polynya of this magnitude could significantly affect global abyssal ocean properties via increased Antarctic Bottom Water (AABW) formation and large Weddell Sea water mass property perturbations. However, the scarcity of 1970s Weddell Sea observations, coupled with the sparseness of abyssal ocean observations, make it difficult to study this phenomenon's oceanic impact without models. This dissertation examines the influence of Weddell Polynyas on abyssal ocean water mass properties and circulation using the GFDL CM2G coupled climate model.
Abyssal ocean temperature, salinity, and water mass changes resulting from Weddell Polynyas are quantified in CM2G and compared to observations. The model polynyas initially cool the abyssal Southern Ocean and South Atlantic, but 2-3 decades after polynya cessation the same regions warm as they relax toward their mean state. Composites of multiple, spontaneously-occurring polynyas in CM2G reveal that up to 10% of recently observed warming in the abyssal Southern Ocean could be the result of the 1970s Weddell Polynya recovery.
Weddell Polynya transport mechanisms are also investigated. Polynya signal transport is governed by two processes acting on different timescales and spreading at different rates: 1) topographic and planetary waves that act on interannual-to-decadal timescales, and 2) advection that acts on decadal-to-centennial timescales. Both mechanisms generate property changes on isobaths. Despite different spreading rates, the advective and wave signals act contemporaneously in many Southern Hemisphere abyssal basins. The combined effect and relative magnitude of the two signals dictates the prevailing property changes.
During Weddell Polynyas, vigorous exchange occurs between the surface and deep waters, resulting in increased abyssal ventilation. In climate models, ideal age tracer is often used to investigate oceanic ventilation. This tracer suffers from several flaws that detract from its suitability as a ventilation diagnostic. We develop a new tracer, ?-age, that rectifies some of ideal age's problematic aspects and examine its utility in an offline tracer model.
Berkman, Paul Arthur, A. J. T. Jull, and Toshio Nakamura. "Old water in the ocean : the Antarctic radiocarbon reservoir." 名古屋大学年代測定資料研究センター 天然放射性元素測定小委員会, 2000. http://hdl.handle.net/2237/13469.
Full textSilva, Tiago Araújo Marques da. "Quantifying Antarctic icebergs and their melting in the ocean." Thesis, University of Sheffield, 2006. http://etheses.whiterose.ac.uk/14902/.
Full textVan, Horsten Natasha. "Photosynthetic response of Southern Ocean phytoplankton under iron and light limitations : bioassay experiments." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97861.
Full textENGLISH ABSTRACT: The Southern Ocean (SO) is of significant interest in the understanding of the global carbon cycle and therefore many studies have been conducted to determine the limiting factors controlling the biological pump within the region. During photosynthesis phytoplankton require various nutrients such as NO3, PO4, inorganic carbon and the micronutrient Fe. The SO is a High-Nutrient Low-Chlorophyll region, therefore no macronutrient limitation is experienced by resident phytoplankton but instead the micronutrient Fe is a significant limiting factor within these waters due to limited inputs. Due to deep mixed layer depths, ice cover, low sun angles and cloud cover throughout parts of the year, light is also considered a limiting factor in the SO. Fe and light limitation cause a decrease in photosynthetic efficiency and therefore a decrease in carbon fixation capabilities. During this study we conducted five bioassay shipboard incubation experiments during two cruises along the Greenwich meridian between South Africa and the ice edge, SOSCEx during March and SAFePool during January to February, in which we varied Fe concentrations and light levels to determine the effects of Fe and light limitation or co-limitation within resident phytoplankton. Spatial and temporal variations in phytoplankton response were studied to determine varying effects of limitation across water masses and different stages of bloom decline within the study area. The combined addition of Fe and light gave the largest increase in biomass, photosynthetic capacity and nutrient uptake. In support of the hypotheses tested changes in the photosynthetic apparatus led to changes in the photosynthetic efficiency and growth of the SO phytoplankton, as a result of variations in Fe and light availability. Variability was also observed in the response of phytoplankton to Fe and light amendments due to spatial and temporal variation in resident phytoplankton communities. It was therefore concluded that both Fe and light are significant controls in the resident phytoplankton photosynthetic apparatus, photosynthetic capabilities, organic carbon fixation and therefore the biogeochemical cycles within the Atlantic sector of the SO.
AFRIKAANSE OPSOMMING: Die Suidelike Oseaan (SO) is van beduidende belang in die begrip van die globale koolstofsiklus en dus is baie studies gedoen om die beperkende faktore te bepaal wat die biologiese pomp in die streek beheer. Tydens fotosintese benodig fitoplankton verskillende voedingstowwe soos NO3, PO4, anorganiese koolstof en die mikrovoedingstof Fe. Die SO is 'n High-Nutrient Lae-Chlorofil streek, dus word geen makrovoedingstof beperking ervaar deur inwoner fitoplankton maar in plaas daarvan is die mikrovoedingstof Fe 'n beduidende beperkende faktor binne hierdie waters weens beperkte insette. As gevolg van diep gemengde laag dieptes, ysbedekking, lae son hoeke en wolkbedekking deur dele van die jaar, word lig ook beskou as 'n beperkende faktor in die SO. Fe en lig beperking veroorsaak 'n afname in die fotosintetiese doeltreffendheid en dus 'n afname in koolstof binding vermoëns. Tydens hierdie studie het ons vyf biotoets inkubasie eksperimente aan boord die skeep gedoen tydens twee vaarte langs die Greenwich meridiaan tussen Suid-Afrika en die ys rand, SOSCEx gedurende Maart en SAFePool gedurende Januarie tot Februarie, waarin ons Fe konsentrasies en lig vlakke gewissel het om die gevolge van Fe en lig beperking, of medebeperking, binne inwoner fitoplankton te bepaal. Ruimtelike en temporale variasies in fitoplankton reaksie was bestudeer om wisselende gevolge van die beperking oor watermassas en verskillende stadiums van bloei afname in die studie area te bepaal. Die gekombineerde byvoeging van Fe en lig het die grootste toename in biomassa, fotosintetiese kapasiteit en voedingsopname gegee. Ter ondersteuning van die getoetste hipoteses, veranderinge in die fotosintetiese apparaat het gelei tot veranderinge in die fotosintetiese doeltreffendheid en groei van die SO fitoplankton, as 'n gevolg van variasies in Fe en lig beskikbaarheid. Veranderlikheid is ook waargeneem in die reaksie van fitoplankton om Fe en lig wysigings weens die ruimtelike en tydelike variasie in inwoner fitoplankton gemeenskappe. Dus was dit by die gevolgtrekking gekom dat beide Fe en lig beduidende kontrole in die inwoner fitoplankton fotosintetiese apparaat, fotosintetiese vermoëns, organiese koolstof binding en daarom die biogeochemiese siklusse binne die Atlantiese sektor van die SO.
Burton, Kenneth R. Jr. "Influence of Antarctic oscillation on intraseasonal variability of large-scale circulations over the Western North Pacific." Thesis, Monterey California. Naval Postgraduate School, 2005. http://hdl.handle.net/10945/2310.
Full textThis study examines Southern Hemisphere mid-latitude wave variations connected to the Antarctic Oscillation (AAO) to establish connections with the 15- to 25-day wave activity in the western North Pacific monsoon trough region. The AAO index defined from the leading empirical orthogonal functions of 700 hPa height anomalies led to seven distinct circulation patterns that vary in conjunction with the 15- to 25-day monsoon trough mode. For nearly one half of the significant events the onset of 15- to 25-day monsoon trough convective activity coincided with a peak negative AAO index and the peak in monsoon trough convection coincided with a peak positive index. The remaining events either occur when the AAO is not significantly varying or when the AAO-related Southern Hemisphere mid-latitude circulations do not match 15- to 25-day transitions. When a significant connection occurs between the Southern Hemisphere mid-latitude circulations related to the AAO and the 15- to 25-day wave activity in the western North Pacific monsoon trough, the mechanism is via equatorward Rossby-wave dispersion. When wave energy flux in the Southern Hemisphere is directed zonally, no connection is established between the AAO and the alternating periods of enhanced and reduced convection in the western North Pacific monsoon trough.
Captain, United States Air Force
Makowski, Jessica. "Understanding Transport Variability of the Antarctic Circumpolar Current Using Ocean Bottom Pressure." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4915.
Full textHughes, Christopher William. "The effect of topography on ocean flow." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:37b3f6b2-ce5f-45b3-b2ed-3325518b06bb.
Full textSinha, Bablu. "The influence of mesoscale eddies and topography on southern ocean flow." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239650.
Full textGregory, Thomas R. "Holocene sea ice-ocean-climate variability from Adélie Land, East Antarctica." Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/41566/.
Full textStewart, Craig Lincoln. "Ice-ocean interactions beneath the north-western Ross Ice Shelf, Antarctica." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274361.
Full textMoffat, Varas Carlos F. "Ocean circulation and dynamics on the west Antarctic Peninsula continental shelf." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42104.
Full textIncludes bibliographical references (p. 177-186).
Observations of current velocity, temperature, salinity and pressure from a 2-year moored array deployment and four hydrographic cruises conducted by the United States Southern Ocean GLOBEC program on the western Antarctic Peninsula continental shelf are used to characterize the ocean circulation and its connection to fresh water and heat fluxes on the shelf. Mean velocities on the shelf are of the order of 5 cm/s or less. Tidal motions are dominated by the M2 and S2 semi-diurnal tides and the 01 and K1 diurnal tides, although the tidal velocities are typically less than 2 cm/s. Near-inertial motions are relatively large, with current velocities as high as 26 cm/s. It is shown that Marguerite Trough, a large bathymetric feature connecting the shelf-break to Marguerite Bay, plays a critical role in determining the circulation. The mean flow is strongly steered in the along-slope direction, and the tidal currents also show increasing current polarization at depth in Marguerite Trough. At time-scales of 5 to 20 days, the observations show bottom-intensified motion in Marguerite Trough consistent with bottom-trapped topographic Rossby waves.
(cont.) The subtidal circulation in the trough has a significant wind-driven component in Marguerite Trough, with downwelling-favorable winds forcing cross-shelf flow on the northern side of the trough and along the shore on the outer shelf. Upwelling-favorable winds force roughly the opposite circulation. The cyclonic circulation on the trough helps advect blobs of salty, warm and nutrient-rich water across the shelf. These intrusions are small (;4 km) and frequent (4 events/month). Also, the Antarctic Peninsula Coastal Current (APCC), a coastal buoyant current which is described for the first time here. The APCC is a seasonal current which is only present during the ice-free season and is forced by freshwater fluxes associated with large glacier melt and precipitation rates in the region.
by Carlos F. Moffat Varas.
Ph.D.
Lukáč, Danica. "Community structure and predation impact of carnivorous macrozooplankton in the polar frontal zone (Southern Ocean), with particular reference to chaetognaths." Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005336.
Full textGoddard, Paul Brent, and Paul Brent Goddard. "Oceanic Controls of North American East Coast Sea Level Rise and Ocean Warming of the Antarctic Shelf." Diss., The University of Arizona, 2018. http://hdl.handle.net/10150/626684.
Full textRenaudie, Johan. "A synthesis of Antarctic Neogene radiolarians." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16985.
Full textThe Southern Ocean is the key to understand the Neogene climate evolution. Unfortunately the lack of a robust geochronological framework has hindered precise studies. Equally of interest is understanding how planktonic communities changed in relation with the evolution of these environments. Radiolarians are abundant in Antarctic Neogene sediments, diversified and consistently well-preserved. They should constitute not only an ideal testing ground for paleobiological studies but also a major resource for improved biostratigraphy. In this study, a quantitative, taxonomically-complete dataset have been collected in various sites of the Southern Ocean, using 98 samples and ca. 7000 specimens per sample. Ca. 500 species were uncovered in this fauna, including 120 new to science. The study of the macroevolutionary history of this fauna reveals that a significant, extinctionless ecological turnover, linked to a decrease in the evenness of the species'' abundances and the rise of genus Antarctissa to dominance, occured at ca. 8 Ma, followed 3 My later by a significant diversity loss. Although the ecological event can be tentatively associated with a regional change in the composition of primary producers, the triggering event of the diversity loss is yet to be found. The whole-fauna diversity history was compared to paleodiversity reconstructions computed using subsampling methodologies from the occurrences gathered in the Neptune database. The comparison shows that the main trends are retrieved by the subsampling procedures but also that substantial distortions make them poorly suited for detailed studies. Finally a biostratigraphical analysis was conducted on this whole-fauna dataset for the late Miocene - Pliocene sequence. Although this analysis is still very much preliminary, it shows a coherent readjustement of the current age models by more than 1 My. This study also shows that 94 events seem reliable enough to be used to correlate Southern Ocean sites together.
Petty, A. A. "Sea ice and the ocean mixed layer over the Antarctic continental shelf." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1417883/.
Full textDierckx, Marie. "Marine ice rheology from deformation experiments of ice shelf samples using a pneumatic compression device: implications for ice shelf stability." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209505.
Full textThe principal objective being to include realistic mechanical parameters for marine ice in ice shelf flow models, uniaxial compression experiments have been performed on various types of marine ice samples. Technical developments are an important component of this thesis has they were necessary to equip the laboratory with the appropriate tools (pneumatic rig, automatic ice fabric data handling).
Results from experimental compression on isotropic marine ice show that it represents the higher boundary for meteoric ice viscosity throughout the whole temperature range, thereby validating Cuffey and Paterson's relationship with an enhancement factor equals to 1.
Marine ice is however often quite anisotropic, showing elongated crystals and wide single maximum fabric, that should impact its mechanical properties. Experiments on pre-oriented marine ice samples have therefore been carried out combining the study of epsilon_{oct} vs. tau_{oct} with a thorough analysis of microstructural data 'before' and 'after' the experiment.
Depending on the orientation of the sample in the applied stress field and on the intensity of the latter, anisotropic marine ice can be harder or softer than its isotropic counterpart, with n=4 often observed in Glen's flow law. Associating the experimental geometrical settings to potential natural equivalent, results suggest that anisotropic marine ice would strengthen ice shelf flow in most areas (for a same given temperature), apart from suturing areas between individual ice streams as they merge to form the ice shelf, where it could become weaker than meteoric ice in certain circumstances.
Finally, preliminary sensitivity studies, using a simple ice shelf model with our experimental parameters of Glen's flow law have allowed us to discuss the potential impact of rift location, rift size and thermal regime in the ice shelf behavior.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Mei, M. Jeffrey(Ming-Yi Jeffrey). "Morphological approaches to understanding Antarctic Sea ice thickness." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129062.
Full textCataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 181-198).
Sea ice thickness has long been an under-measured quantity, even in the satellite era. The snow surface elevation, which is far easier to measure, cannot be directly converted into sea ice thickness estimates without knowledge or assumption of what proportion of the snow surface consists of snow and ice. We do not fully understand how snow is distributed upon sea ice, in particular around areas with surface deformation. Here, we show that deep learning methods can be used to directly predict snow depth, as well as sea ice thickness, from measurements of surface topography obtained from laser altimetry. We also show that snow surfaces can be texturally distinguished, and that texturally-similar segments have similar snow depths. This can be used to predict snow depth at both local (sub-kilometer) and satellite (25 km) scales with much lower error and bias, and with greater ability to distinguish inter-annual and regional variability than current methods using linear regressions. We find that sea ice thickness can be estimated to <20% error at the kilometer scale. The success of deep learning methods to predict snow depth and sea ice thickness suggests that such methods may be also applied to temporally/spatially larger datasets like ICESat-2.
by M. Jeffrey Mei.
Ph. D.
Ph.D. Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Department of Aeronautics and Astronautics; and the Woods Hole Oceanographic Institution)
Dumont, Isabelle. "Interactions between the microbial network and the organic matter in the Southern Ocean: impacts on the biological carbon pump." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210300.
Full textThe Southern Ocean (ca. 20% of the world ocean surface) is a key place for the regulation of Earth climate thanks to its capacity to absorb atmospheric carbon dioxide (CO2) by physico-chemical and biological mechanisms. The biological carbon pump is a major pathway of absorption of CO2 through which the CO2 incorporated into autotrophic microorganisms in surface waters is transferred to deep waters. This process is influenced by the extent of the primary production and by the intensity of the remineralization of organic matter along the water column. So, the annual cycle of sea ice, through its in situ production and remineralization processes but also, through the release of microorganisms, organic and inorganic nutrients (in particular iron)into the ocean has an impact on the carbon cycle of the Southern Ocean, notably by promoting the initiation of phytoplanktonic blooms at time of ice melting.
The present work focussed on the distribution of organic matter (OM) and its interactions with the microbial network (algae, bacteria and protozoa) in sea ice and ocean, with a special attention to the factors which regulate the biological carbon pump of the Southern Ocean. This thesis gathers data collected from a) late winter to summer in the Western Pacific sector, Western Weddell Sea and Bellingshausen Sea during three sea ice cruises ARISE, ISPOL-drifting station and SIMBA-drifting station and b) summer in the Sub-Antarctic and Polar Front Zone during the oceanographic cruise SAZ-Sense.
The sea ice covers were typical of first-year pack ice with thickness ranging between 0.3 and 1.2 m, and composed of granular and columnar ice. Sea ice temperature ranging between -8.9°C and -0.4°C, brines volume ranging between 2.9 to 28.2% and brines salinity from 10 to >100 were observed. These extreme physicochemical factors experienced by the microorganisms trapped into the semi-solid sea ice matrix therefore constitute an extreme change as compared to the open ocean. Sea ice algae were mainly composed of diatoms but autotrophic flagellates (such as dinoflagellates or Phaeocystis sp.) were also typically found in surface ice layers. Maximal algal biomass was usually observed in the bottom ice layers except during SIMBA where the maxima was localised in the top ice layers likely because of the snow and ice thickness which limit the light available in the ice cover. During early spring, the algal growth was controlled by the space availability (i.e. brine volume) while in spring/summer (ISPOL, SIMBA) the major nutrients availability inside sea ice may have controlled algal growth. At all seasons, high concentrations of dissolved and particulate organic matter were measured in sea ice as compared to the water column. Dissolved monomers (saccharides and amino acids) were accumulated in sea ice, in particular in winter. During spring and summer, polysaccharides constitute the main fraction of the dissolved saccharides pool. High concentrations of transparent exopolymeric particles (TEP), mainly constituted with saccharides, were present and their gel properties greatly influence the internal habitat of sea ice, by retaining the nutrients and by preventing the protozoa grazing pressure, inducing therefore an algal accumulation. The composition as well as the vertical distribution of OM in sea ice was linked to sea ice algae.
Besides, the distribution of microorganisms and organic compounds in the sea ice was also greatly influenced by the thermodynamics of the sea ice cover, as evidenced during a melting period for ISPOL and during a floodfreeze cycle for SIMBA. The bacteria distribution in the sea ice was not correlated with those of algae and organic matter. Indeed, the utilization of the accumulated organic matter by bacteria seemed to be limited by an external factor such as temperature, salinity or toxins rather than by the nature of the organic substrates, which are partly composed of labile monomeric saccharides. Thus the disconnection of the microbial loop leading to the OM accumulation was highlighted in sea ice.
In addition the biofilm formed by TEP was also involved in the retention of cells and other compounds(DOM, POM, and inorganic nutrients such as phosphate and iron) to the brine channels walls and thus in the timing of release of ice constituents when ice melts. The sequence of release in marginal ice zone, as studied in a microcosm experiments realized in controlled and trace-metal clean conditions, was likely favourable to the development of blooms in the marginal ice zone. Moreover microorganisms derived from sea ice (mainly <10 µm) seems able to thrive and grow in the water column as also the supply of organic nutrients and Fe seems to benefit to the pelagic microbial community.
Finally, the influence of the remineralization of organic matter by heterotrophic bacterioplankton on carbon export and biological carbon pump efficiency was investigated in the epipelagic (0-100 m) and mesopelagic(100-700 m) zones during the summer in the sub-Antarctic and Polar Front zones (SAZ and PFZ) of the Australian sector (Southern Ocean). Opposite to sea ice, bacterial biomass and activities followed Chl a and organic matter distributions. Bacterial abundance, biomass and activities drastically decreased below depths of 100-200 m. Nevertheless, depth-integrated rates through the thickness of the different water masses showed that the mesopelagic contribution of bacteria represents a non-negligible fraction, in particular in a diatom-dominated system./
L’océan Antarctique (± 20% de la surface totale des océans) est un endroit essentiel pour la régulation du climat de notre planète grâce à sa capacité d’absorber le dioxyde de carbone (CO2) atmosphérique par des mécanismes physico-chimique et biologique. La pompe biologique à carbone est un processus majeur de fixation de CO2 par les organismes autotrophes à la surface de l’océan et de transfert de carbone organique vers le fond de l’océan. Ce processus est influencé par l’importance de la production primaire ainsi que par l’intensité de la reminéralisation de la matière organique dans la colonne d’eau. Ainsi, le cycle annuel de la glace via sa production/reminéralisation in situ mais aussi via l’ensemencement de l’océan avec des microorganismes et des nutriments organiques et inorganiques (en particulier le fer) a un impact sur le cycle du carbone dans l’Océan Antarctique, notamment en favorisant l’initiation d’efflorescences phytoplanctoniques dans la zone marginale de glace.
Plus précisément, nous avons étudié les interactions entre le réseau microbien (algues, bactéries et protozoaires) et la matière organique dans le but d’évaluer leurs impacts potentiels sur la pompe biologique de carbone dans l’Océan Austral. Deux écosystèmes différents ont été étudiés :la glace de mer et le milieu océanique grâce à des échantillons prélevés lors des campagnes de glace ARISE, ISPOL et SIMBA et lors de la campagne océanographique SAZ-Sense, couvrant une période allant de la fin de l’hiver à l’été.
La glace de mer est un environnement très particulier dans lequel les microorganismes planctoniques se trouvent piégés lors de la formation de la banquise et dans lesquels ils subissent des conditions extrêmes de température et de salinité, notamment. Les banquises en océan ouvert étudiées (0,3 à 1,2 m d’épaisseur, températures de -8.9°C à -0.4°C, volumes relatifs de saumure de 2.9 à 28.2% et salinités de saumures entre 10 et jusque >100) étaient composées de glace columnaire et granulaire. Les algues de glace étaient principalement des diatomées mais des flagellés autotrophes (tels que des dinoflagellés ou Phaeocystis sp.) ont été typiquement observés dans les couches de glace de surface. Les biomasses algales maximales se trouvaient généralement dans la couche de glace de fond sauf à SIMBA où les maxima se trouvaient en surface, probablement en raison de l’épaisseur des couches de neige et de glace, limitant la lumière disponible dans la colonne de glace. Au début du printemps, la croissance algale était contrôlée par l’espace disponible (càd le volume des saumures) tandis qu’au printemps/été, la disponibilité en nutriments majeurs a pu la contrôler. A toutes les saisons, des concentrations élevées en matière organique (MO) dissoute et particulaire on été mesurées dans la glace de mer par rapport à l’océan. Des monomères dissous (sucres et acides aminés) étaient accumulés dans la glace, surtout en hiver. Au printemps et été, les polysaccharides dissous dominaient le réservoir de sucres. La MO était présente sous forme de TEP qui par leurs propriétés de gel modifie l’habitat interne de la glace. Ce biofilm retient les nutriments et gêne le mouvement des microorganismes. La composition et la distribution de la MO dans la glace étaient en partie reliées aux algues de glace. De plus, la thermodynamique de la couverture de glace peut contrôler la distribution des microorganismes et de la MO, comme observé lors de la fonte de la glace à ISPOL et lors du refroidissement de la banquise à SIMBA. La distribution des bactéries n’est pas corrélée avec celle des algues et de la MO dans la glace. En effet, la consommation de la MO par les bactéries semble être limitée non pas par la nature chimique des substrats mais par un facteur extérieur affectant le métabolisme bactérien tel que la température, la salinité ou une toxine. Le dysfonctionnement de la boucle microbienne menant à l’accumulation de la MO dans la glace a donc été mis en évidence dans nos échantillons.
De plus, le biofilm formé par les TEP est aussi impliquée dans l’attachement des cellules et autres composés aux parois des canaux de saumure et donc dans la séquence de largage lors de la fonte. Cette séquence semble propice au développement d’efflorescences phytoplanctoniques dans la zone marginale de glace. Les microorganismes originaires de la glace (surtout ceux de taille < 10 μm) semblent capables de croître dans la colonne d’eau et l’apport en nutriments organiques et inorganiques apparaît favorable à la croissance des microorganismes pélagiques.
Enfin, l’influence des activités hétérotrophes sur l’export de carbone et l’efficacité de la pompe biologique à carbone a été évaluée dans la couche de surface (0-100 m) et mésopélagique (100-700 m) de l’océan. Au contraire de la glace, les biomasses et activités bactériennes suivaient les distributions de la chlorophyll a et de la MO. Elles diminuent fortement en dessous de 100-200 m, néanmoins les valeurs intégrées sur la hauteur de la colonne d’eau indiquent que la reminéralisation de la MO par les bactéries dans la zone mésopélagique est loin d’être négligeable, spécialement dans une région dominée par les diatomées.
Doctorat en Sciences agronomiques et ingénierie biologique
info:eu-repo/semantics/nonPublished
Griffith, Gary P., and n/a. "The photoprotective xanthophyll cycle in Southern Ocean phytoplankton and Antarctic sea-ice algae." University of Otago. Department of Marine Science, 2008. http://adt.otago.ac.nz./public/adt-NZDU20080704.111758.
Full textMcNaught, Pamela J. "The United States, the South Atlantic, and Antarctica : interests and challenges /." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237990.
Full textThesis Advisor(s): Bruneau, Thomas C. Second Reader: Breemer, Jan S. "June 1990." DTIC Identifier(s): International politics, Treaties, Security, Cooperation, South America, South Africa, Competition, Natural resources, Sea lanes of communication, Naval operations, Foreign policy, Balance of power, Sovereignty, Spheres of influence, National interests. Author(s) subject terms: U.S. Interests, South Atlantic, Southern Cone, Antarctica. Includes bibliographical references (p. 101-104). Also available online.
Hunt, Richard Jeffrey. "Ice-ocean-atmosphere interactions at high latitudes in the southern hemisphere." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307309.
Full textBoodhraj, Kirodh. "Investigating the sensitivity of one-dimensional turbulence schemes in the sub-Antarctic Southern Ocean." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/27913.
Full textStuart, Keith Mitchell. "Application of SeaWinds Scatterometer Data to the Study of Antarctic Icebergs." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3371.
Full textSleadd, Isaac Martin. "CCAAT/Enhancer-Binding Protein Delta (C/EBP-delta) Expression in Antarctic Fishes: Implications for Cell Cycle and Apoptosis." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/994.
Full textMcMillan, Malcolm John. "Satellite investigations of ice-ocean interactions in the Amundsen Sea sector of West Antarctica." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6242.
Full textButterworth, Brian J. "Air-sea carbon dioxide exchange in the Southern Ocean and Antarctic Sea ice zone." Thesis, State University of New York at Albany, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10149297.
Full textThe Southern Ocean is an important part of the global carbon cycle, responsible for roughly half of the carbon dioxide (CO2) absorbed by the global ocean. The air-sea CO2 flux (Fc) can be expressed as the product of the water-air CO2 partial pressure difference (ΔpCO2) and the gas transfer velocity ( k), an exchange coefficient which represents the efficiency of gas exchange. Generally, Fc is negative (a sink) throughout the Southern Ocean and Antarctic sea ice zone (SIZ), but uncertainty in k has made it difficult to develop an accurate regional carbon budget. Constraining the functional dependence of k on wind speed in open water environments, and quantifying the effect of sea ice on k, will reduce uncertainty in the estimated contribution of the Southern Ocean and Antarctic SIZ to the global carbon cycle.
To investigate Fc in the Southern Ocean, a ruggedized, unattended, closed-path eddy covariance (EC) system was deployed on the Antarctic research vessel Nathaniel B. Palmer for nine cruises during 18 months from January 2013 to June 2014 in the Southern Ocean and coastal Antarctica. The methods are described and results are shown for two cruises chosen for their latitudinal range, inclusion of open water and sea ice cover, and large ΔpCO2. The results indicated that ship-based unattended EC measurements in high latitudes are feasible, and recommendations for deployments in such environments were provided.
Measurements of Fc and ΔpCO2 were used to compute k. The open water data showed a quadratic relationship between k (cm hr–1) and the neutral 10-m wind speed (U10n, m s –1), k=0.245 U10n 2+1.3, in close agreement with tracer-based results and much lower than previous EC studies. In the SIZ, it was found that k decreased in proportion to sea ice cover. This contrasted findings of enhanced Fc in the SIZ by previous open-path EC campaigns. Using the NBP results a net annual Southern Ocean (ocean south of 30°S) carbon flux of –1.1 PgC yr–1 was calculated.
Li, Lingwei. "Understanding Antarctic Circumpolar Current Transport at the LGM Using an Isotope-enabled Ocean Model." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555594394056462.
Full textKosempa, Michael. "Southern Ocean Transport by Combining Satellite Altimetry and Temperature/Salinity Profile Data." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6658.
Full textBernard, Kim Sarah. "Mesozooplankton community structure and grazing impact in the polar frontal zone of the Southern Ocean." Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1005417.
Full textBernard, Kim Sarah. "The role of the euthecosome pteropod, limacina retroversa, in the polar frontal zone, Southern Ocean." Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1005449.
Full textHenley, Sian Frances. "Climate-induced changes in carbon and nitrogen cycling in the rapidly warming Antarctic coastal ocean." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7626.
Full textKobo, Nomkwezane Sanny. "Interaction of the antarctic circumpolar current with topography: impacts on the Southern Ocean eddy dynamics." Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/6677.
Full textOlsen, Elisabeth, Cerf Christopher De, Godwin Dziwornu, Eleonora Puccinelli, Shirley Parker-Nance, Isabelle Ansorge, Toufiek Samaai, Laura Dingle, Adrienne Lesley Edkins, and Suthananda Sunassee. "Cytotoxic activity of marine sponge extracts from the sub-Antarctic Islands and the Southern Ocean." South African Journal of Science, 2016. http://hdl.handle.net/10962/66300.
Full textOver the past 50 years, marine invertebrates, especially sponges, have proven to be a valuable source of new and/or bioactive natural products that have the potential to be further developed as lead compounds for pharmaceutical applications. Although marine benthic invertebrate communities occurring off the coast of South Africa have been explored for their biomedicinal potential, the natural product investigation of marine sponges from the sub-Antarctic Islands in the Southern Ocean for the presence of bioactive secondary metabolites has been relatively unexplored thus far. We report here the results for the biological screening of both aqueous and organic extracts prepared from nine specimens of eight species of marine sponges, collected from around Marion Island and the Prince Edward Islands in the Southern Ocean, for their cytotoxic activity against three cancer cell lines. The results obtained through this multidisciplinary collaborative research effort by exclusively South African institutions has provided an exciting opportunity to discover cytotoxic compounds from sub-Antarctic sponges, whilst contributing to our understanding of the biodiversity and geographic distributions of these cold-water invertebrates. Therefore, we acknowledge here the various contributions of the diverse scientific disciplines that played a pivotal role in providing the necessary platform for the future natural products chemistry investigation of these marine sponges from the sub- Antarctic Islands and the Southern Ocean. Significance: This study will contribute to understanding the biodiversity and geographic distributions of sponges in the Southern Ocean. This multidisciplinary project has enabled the investigation of marine sponges for the presence of cytotoxic compounds. Further investigation will lead to the isolation and identification of cytotoxic compounds present in the active sponge extracts.
University of Cape Town; South African Medical Research Council; National Research Foundation (South Africa); CANSA; Rhodes University; Department of Science and Technology; Department of Environmental Affairs; SANAP
Burton, Kenneth R. "Influence of Antarctic oscillation on intraseasonal variability of large-scale circulations over the Western North Pacific /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FBurton.pdf.
Full textNankivell, Adrian P. "Tectonic evolution of the Southern Ocean between Antarctica, South America and Africa over the past 84Ma." Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:c7a38be2-1973-47ff-9d4e-f4e76d227d46.
Full textKuyper, Drikus. "Changes in communities of Hydrozoa (Siphonophorae and Hydromedusae) across the Atlantic sector of the Southern Ocean." University of the Western Cape, 2020. http://hdl.handle.net/11394/7740.
Full textRao, Deepa Ph D. Massachusetts Institute of Technology. "Characterizing cobalamin cycling by Antarctic marine microbes across multiple scales." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127908.
Full textCataloged from the official PDF of thesis.
Includes bibliographical references (pages 161-183).
Highly productive marine microbial communities in the coastal Southern Ocean sustain the broader Antarctic ecosystem and play a key role in Earth's climate via the biological pump. Regional phytoplankton growth is primarily limited by iron and co-limited by cobalamin (vitamin B₁₂), a trace cobalt-containing organometallic compound only synthesized by some bacteria and archaea. These micronutrients impact primary production and the microbial ecology of the two keystone phytoplankton types: diatoms and Phaeocystis antarctica. This thesis investigates microbe-driven cobalamin cycling in Antarctic seas across multiple spatiotemporal scales. I conducted laboratory culture experiments with complementary proteomics and transcriptomics to investigate the B₁₂-ecophysiology of P. antarctica strain CCMP 1871 morphotypes under iron-B₁₂ co-limitation.
We observed colony formation under higher iron treatments, and a facultative use of B₁₂-dependent (MetH) and B₁₂-independent (MetE) methionine synthase isoforms in response to vitamin availability, demonstrating that this strain is not B₁₂-auxotrophic. Through comparative 'omics, we identified a putative MetE protein in P. antarctica abundant under low B₁₂, which is also found in other marine microbes. Across Antarctic seas, community-scale cobalt and B₁₂ uptake rates were measured by ⁵⁷Co radiotracer incubation experiments and integrated with hydrographic and phytoplankton pigment data. I observed significant correlations between uptake fluxes and environmental variables, providing evidence for predominantly diatom-driven uptake of these micronutrients in warmer, fresher surface waters with notable regional differences.
To date, this work is the most comprehensive attempt to elucidate the processes governing the co-cycling of cobalt and B₁₂ in any marine system. At the ecosystem-scale, I developed and tested a hypothesis of micronutrient-driven community dynamics through a trait-based model with cross-feeding interactions. The model demonstrates how the observed seasonal succession of springtime P. antarctica from solitary to colonial cells, bacterioplankton, and summertime diatoms may be explained by the microbial cycling of iron, dissolved organic carbon, and B₁₂. Overall, this dissertation provides new information about the micronutrient-driven ecology of Antarctic marine microbes and adds to our understanding of the interconnections between organismal life cycle, trace metals, and trace organics in marine environments.
by Deepa Rao.
Ph. D.
Ph.D. Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution)
Bernard, Anthony Thomas Firth. "Euphausiid population structure and grazing in the Indian sector of the Antarctic Polar Frontal Zone, during austral autumn." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1015960.
Full textPasquer, Bénédicte. "Modélisation de la pompe biologique de carbone dans l'Océan Austral." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210937.
Full textFripiat, François. "Isotopic approaches in the silicon cycle: the Southern Ocean case study." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210187.
Full text(1) A new mass spectrometer method (HR-SF-ICPMS) has been developed for 30Si-isotopic abundance measurements. This methodology is faster and easier than the previous available methodologies and has the same precision. A complete set of incubation was coupled with parallel 32Si-incubations and the two methodologies give not significantly different bSiO2 production rates. In the Southern Ocean, especially in the southern Antarctic Circumpolar Current, the large silicic acid concentration degrades the sensitivity of the method with Si dissolution fluxes staying generally below the detection limit. In contrast, the 28Si-isotopic dilution was sensitive enough to assess low biogenic silica dissolution rates in silicic acid poor waters of the northern ACC. We show that large accumulation of detrital dissolving biogenic silica after productive period implies really efficient silicon loop with integrated (euphotic layer) dissolution:production ratio equal or larger than 1.
(2) We largely expand the silicic acid isotopic data in the open ocean. Relatively simple mass and isotopic balances have been performed in the Antarctic Zone and have allowed to apply for the first time ä30Si in a quantitative way to estimate regional net silica production and quantify source waters fueling bSiO2 productivity. We observe that at the end of the productive period as suggested with 30Si-incubation, large accumulation of detrital biogenic silica in the surface waters increase the D:P ratio and subsequently dampens the bSiO2 production mediated isotopic fractionation with residual biogenic silica carrying heavier ä30Si than expected. Seasonal isotopic evolution is simulated and seems in agreement with our observations. These simulations strongly suggest working with non-zero order equations to fully assess the seasonal expression of the different processes involved: mixing, uptake, dissolution. Si-isotopes are also tracking the origin and fates of the different ACC pools across the Southern Ocean meridional circulation. Moreover during the circumpolar eastward pathway, the bSiO2 dissolution in deep water decreases the corresponding ä30Si values and this imprint is further transmitted via the upper limb of the meridional circulation in the intermediate water masses.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Sterley, Jessica Anne. "Trophodynamics of carnivorous zooplankton in the region of the subtropical convergence within the Indian sector of the Southern Ocean, with particular emphasis on chaetognaths." Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1005478.
Full text