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1
Newton, Anthony. "Ocean-transported pumice in the North Atlantic." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/22518.
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The aims of this study are to identify the sources of the widespread Holocene deposits of pumice found along the coasts of the North Atlantic region and the age of the source eruptions. Previous research has failed to positively identify the precise source of this pumice. Fieldwork is carried out in Norway and Iceland to obtain pumice pieces for geochemical analysis. Pumice pieces are recovered from Holocene raised beaches and the height of these deposits above sea-level determined. This establishes the existence of substantial local deposits of Holocene pumice on the raised shorelines of north-western Iceland for the first time. The fieldwork in Norway confirms the presence of multiple levels of brown/black/grey pumice on mid-Holocene Norwegian raised beaches and white pumice on late-glacial/early Holocene shorelines. Pumice is also collected from the slopes of the Katla Volcanic System, southern Iceland, which is identified as a possible source of the dacitic pumice. Archaeological pumice, donated by collaborators, from sites in the British Isles is also analysed. The number of archaeological sites where pumice has been recorded is nearly doubled to almost 150. A collaborative project identifies at least 17 silicic tephra layers (SILK layers) which have been produced by the Katla Volcanic System during the Holocene. Geochemical analyses are performed on the majority of these tephra layers. Over 1500 electron probe microprobe analyses (EPMA) and over 200 Secondary Ion Mass Spectrometry (SIMS) analyses are undertaken on pumice and tephra samples. These are the first high quality grain specific analyses carried out on pumice in the North Atlantic. These analyses establish that the majority of the mid- to late-Holocene pumice found in the study areas is dacitic and produced from the same source. Geochemically different and older pumice also occurs in Mesolithic archaeological sites in Scotland. All of the analysed pumice can be correlated to volcanic activity in Iceland.
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Ellison, Christopher Robert William. "North Atlantic Holocene palaeoceanography : surface and deep ocean variability in the subpolar North Atlantic." Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435126.
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Su, Lin 1966. "Modelling study of nutrients cycles in the North Atlantic Atlantic Ocean." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40002.
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We have coupled a 3-dimensional physical planetary geostrophic ocean general circulation model to different biological models to investigate the interaction between physical and biological processes. A 1-dimensional particle cycle model with two particle size classes has been developed and coupled to the physical model as well.The ocean model (Zhang et al., 1992) is based on the planetary geostrophic equations in spherical coordinates. The model equations include the full prognostic temperature and salinity equations. The momentum equations are diagnostic and include geostrophic balance, and a linear friction term in order to provide a western boundary current. The wind stress is applied at the top level of the model. The temperature and salinity distributions used in the surface boundary restoring condition are taken from climatological data. The model domain consists of a flat-bottomed box of 60$ sp circ$ longitude extending between 5$ sp circ$N and 65$ sp circ$N. The horizontal resolution is 2.3$ sp circ$ in both latitude and longitude with 14 levels in the vertical.
The physical model is first coupled to a biological model where new production is given by a restoring condition of surface nitrate towards its observed concentration. The coupled model is used to examine Martin et al.'s (1987) hypothesis that lateral transport and decomposition of slow or non-sinking organic matter can cause a non-local balance between the remineralization rate and the overlying new production rate in open ocean regions. The role of the Gulf Stream in nutrient transport is examined. The model results agree well with the North Atlantic nutrient transport calculated from observed nutrients and hydrographic data. The model results suggest that the thermohaline overturning circulation and the Gulf Stream horizontal recirculation play an important role in the North Atlantic nutrient distribution.
The physical model is then tested in the seasonal mode, and coupled with a biological model which is based on nitrate limiting the rate of new production. The model simulated seasonal oxygen cycle agrees well with the results of observational studies and 1-dimensional model simulations. The oxygen utilization rate below the euphotic zone provides a useful estimate of new production.
A 1-dimensional time dependent particle cycling model with two particle size classes based on Clegg and Whitfield (1990) is then developed. The simulated total organic carbon concentration and large particle flux are consistent with observations and other 1-dimensional model simulations. The downward transport of organic carbon is mainly accomplished by the fast sinking large particles, which comprise a small fraction of the total particulate mass. The steady state version of the particle model is also coupled with the 3-dimensional physical model. The magnitudes of simulated organic carbon flux and total organic matter concentration are comparable with observations.
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Friedrichs, Marjorie Anne MacWhorter. "Meridional circulation in the tropical North Atlantic /." Online version of thesis as technical report, 1993. http://hdl.handle.net/1912/616.
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Buck, P. J. "Sedimentology and micropalaeontology of gravity cores from the N.E. Atlantic continental slope south west of Ireland." Master's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/17655.
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Bibliography: pages 45-55.Eleven gravity cores from the continental margin off Eire and Land's End (SW England) were examined and found to document the major trends of the Late Pleistocene climate. Several stratigraphic indicators; - carbonate content, sediment texture, grain size, composition, nature of terrigenous components, ice-rafted debris and foraminiferal diversity were examined and show that the glacial history of the study area can be closely correlated with the palaeoclimatic evolution of the adjacent European shelf. Sediments deposited during Late Pleistocene glacial conditions show the following characteristics when compared to the surface sediments deposited under Holocene interglacial conditions: an increase in the quantity of ice-rafted debris and percentage of mica, and a notable increase in the degree of frosting and pitting of the quartz grains. Overall grain size was finer resulting in a silty sediment package. Sedimentologically the cores fall into two groups (1 and 2). The major difference being that Group 1 (located on the Pendragon Escarpment) received increased quantities of fine silts from a 'shelf spill-over' mechanism operating on the Fastnet and Western Approaches Basins, during glacial regressions. All sediment samples displayed polymodal characteristics reflecting the interaction of several different physical processes e.g. ice-rafting, contour currents etc. Striking variations in the populations of planktonic foraminifera were noted, alternating between Arctic and Sub-Arctic assemblages, reflecting the waxing and waning of glacial activity. The coccolith-carbonate minima correlate with the Arctic-fauna maxima and the ¹⁸O/¹⁶O maxima of the oxygen-isotope curves. Foraminiferal-test analysis (ratio of whole foraminifera fragmented foraminifera) revealed that no correlation existed with any of the other parameters analysed. However, the cores were severely affected by the presence of bottom currents which were strong enough to remove the fragmented tests. Parallellaminated contourites and evidence of erosion were noted in all cores. Ten cores penetrated sediments deposited during the last glacial maximum of 20,000 B.P - 18,000 B.P. near the 75cm depth mark (Core 1865 was too short to reach such sediments). However sediments reflecting the 11,000 B.P glacial readvance, detected at around the 25cm mark, were not as clearly represented. Bioturbation has smoothed the climatic record throughout the lengths of these cores and has also suppressed the high-frequency oscillations (<10³ B.P).
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Roberts, Natalie Laura. "Investigating North Atlantic ocean circulation using radiogenic isotopes." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607824.
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Menary, M. B. "Simulating decadal variability in the North Atlantic Ocean." Thesis, University of Reading, 2016. http://centaur.reading.ac.uk/63180/.
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Observations and climate models suggest significant decadal variability within the North Atlantic subpolar gyre (NA SPG), though observations are sparse and models disagree on the details of this variability. Therefore, it is important to understand 1) the mechanisms of simulated decadal variability, 2) which parts of simulated variability are more faithful representations of reality, and 3) the implications for climate predictions. Here, we investigate the decadal variability in the NA SPG in the state-of-the-art, high resolution (0.25◦ ocean resolution), climate model ‘HadGEM3’. We find a decadal mode with a period of 17 years that explains 30% of the annual variance in related indices. The mode arises due to the advection of heat content anomalies, and shows asymmetries in the timescale of phase reversal between positive and negative phases. A negative feedback from temperature-driven density anomalies in the Labrador Sea (LS) allows for the phase reversal. The North Atlantic Oscillation (NAO), which exhibits the same periodicity, amplifies the mode. The atmosphere-ocean coupling is stronger during positive rather than negative NAO states, explaining the asymmetry. Within the NA SPG, there is potential predictability arising partly from this mode for up to 5 years. There are important similarities between observed and simulated variability, such as the apparent role for the propagation of heat content anomalies. However, observations suggest interannual LS density anomalies are salinity-driven. Salinity control of density would change the temperature feedback to the south, possibly limiting real-world predictive skill in the southern NA SPG with this model. Finally, to understand the diversity of behaviours, we analyse 42 present-generation climate models. Temperature and salinity biases are found to systematically influence the driver of density variability in the LS. Resolution is a good predictor of the biases. The dependence of variability on the background state has important implications for decadal predictions.
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Jordan, Richard William. "Coccolithophorid communities in the North-East Atlantic." Thesis, University of Surrey, 1988. http://epubs.surrey.ac.uk/814123/.
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Caccolithopliorids are important members of phytoplankton communities in most parts of the world's oceans. The formation, release and flux of the calcite scales (coccoliths) of these organisms over millions of years, has led to sedimentary deposits of great geological significance. The reporting of immense blooms of coccolithophorids by satellite photography and their passible involvement in atmospheric sulphur emissions has emphasised the necessity for further information on their distribution and ecology. During an extensive sampling programme in the N.E. Atlantic, water samples were collected throughout the photic zone at 30 stations. Scanning electron microscopy of filtered water samples enabled coccolithophorid family and species distributions to be compiled. It was found that certain species assemblages could be assigned to distinct biogeographic zones and that these zones closely conformed to the movements of the N. Atlantic surface currents. However, at the Azores Front it was shown that a transitional region existed between the cold and warm water masses, where the flora of each zone could be found. Detailed studies of coccolithophorid vertical distribution has shown that most species can be assigned to discrete depth bands within the euphotic zone. Furthermore, it was noticed that in two species which have no depth preference, the degree of calcification increased with depth. One of these species, E. huxleyi, displayed two ecomorphotypic variants differing in their calcification, size and morphology. During two east to west transects it was noticed that the halocaccolitiiophorid numbers increased towards the Mid-Atlantic Ridge. A number of new species are described and current taxonomic problems reviewed.
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Parnell-Turner, Ross Ernest. "Observations of transient mantle convection in the North Atlantic Ocean." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648620.
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Bellucci, Alessio. "Free and forced variability in the North Atlantic Ocean." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402041.
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Hartley, Ross Alan. "Cenozoic transient convective uplift of the North Atlantic Ocean." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607889.
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Brearley, James Alexander. "Upper ocean transport variability in the subtropical North Atlantic." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/191959/.
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Many general circulation models predict a reduction in overturning strength in the 21st century as a response to anthropogenic forcing, meaning that novel methods of monitoring individual components of the subtropical North Atlantic circulation are required. This observational study outlines efforts to monitor upper ocean transports near the 36°N latitude line and to identify possible forcing mechanisms. Specifically, an optimal interpolation scheme is employed to synthesise annual and seasonal sections of the Atlantic using T/S data from Argo floats and the Line W array from 2002 to 2007. Combining these data with an estimate of the barotropic velocity yields accurate values of the interior geostrophic transport above 1000 dbar. Close to the western boundary, where errors incurred by the scheme are larger, altimetric SSH differences are used to quantify the Gulf Stream transport above 2000 dbar at 10-day resolution. Finally, a detailed analysis of wind stress and wind stress curl fields of the subtropical North Atlantic is used to estimate both the Ekman and Sverdrup transports and to isolate the dominant time and space scales of variability. The mean zonally integrated interior transport above 1000 dbar between the eastern boundary and the Gulf Stream was -48.0 ± 3.3 Sv, where the error represents the standard error of the seasonal baroclinic transport estimates. The size of the variability between seasons was similar to the interannual variability (standard deviations of 6.6 Sv and 7.7 Sv). Most variability at interannual timescales arises from changes in the density structure of the main thermocline west of 40°W. Neither interannual nor seasonal variability in the interior transport correlate with changes in the Sverdrup transport, though the Sverdrup relation does account for the mean upper ocean transport in the eastern basin. Gulf Stream transport across Line W in the period 2002 to 2008 was estimated to be 87.6 (± 0.8 Sv standard error) in the upper 1000 dbar, with a peak transport in late summer. In line with earlier studies, the seasonal cycle of the transport appears to be correlated with local wind stress curl forcing but determining the precise mechanism requires further theoretical and modelling work.
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Le, Bras Isabela Astiz. "Dynamics of North Atlantic western boundary currents." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109056.
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Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 163-174).
The Gulf Stream and Deep Western Boundary Current (DWBC) shape the distribution of heat and carbon in the North Atlantic, with consequences for global climate. This thesis employs a combination of theory, observations and models to probe the dynamics of these two western boundary currents. First, to diagnose the dynamical balance of the Gulf Stream, a depth-averaged vorticity budget framework is developed. This framework is applied to observations and a state estimate in the subtropical North Atlantic. Budget terms indicate a primary balance of vorticity between wind stress forcing and dissipation, and that the Gulf Stream has a significant inertial component. The next chapter weighs in on an ongoing debate over how the deep ocean is filled with water from high latitude sources. Measurements of the DWBC at Line W, on the continental slope southeast of New England, reveal water mass changes that are consistent with changes in the Labrador Sea, one of the sources of deep water thousands of kilometers upstream. Coherent patterns of change are also found along the path of the DWBC. These changes are consistent with an advective-diffusive model, which is used to quantify transit time distributions between the Labrador Sea and Line W. Advection and stirring are both found to play leading order roles in the propagation of water mass anomalies in the DWBC. The final study brings the two currents together in a quasi-geostrophic process model, focusing on the interaction between the Gulf Stream's northern recirculation gyre and the continental slope along which the DWBC travels. We demonstrate that the continental slope restricts the extent of the recirculation gyre and alters its forcing mechanisms. The recirculation gyre can also merge with the DWBC at depth, and its adjustment is associated with eddy fluxes that stir the DWBC with the interior. This thesis provides a quantitative description of the structure of the overturning circulation in the western North Atlantic, which is an important step towards understanding its role in the climate system.
by Isabela Astiz Le Bras.
Ph. D.
14
Slater, Deborah Ruth. "The transport of Mediterranean water in the North Atlantic Ocean." Thesis, University of Southampton, 2003. https://eprints.soton.ac.uk/426647/.
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Ocean circulation is a fundamental component of the Earth's climate system. The Atlantic thermohaline circulation, driven by deep convection at high latitudes, has a central role in regulating European climate through its transport and redistribution of heat. Either directly or indirectly, Mediterranean Water (MW) provides the high salinities found in the Nordic Seas which are required to precondition for deep convection. The precise mechanisms and pathways remain undetermined and yet are fundamental to understanding the effect that any change in the Mediterranean Outflow may have on circulation and ultimately on climate. This thesis investigates the transport of MW in the North Atlantic Ocean using hydrographic and model data. The primary objective is to quantify how much MW flows northwards and how much flows westwards from its source in the Gulf of Cadiz. Two boxes (Med Boxes) were constructed using hydrographic sections in the eastern North Atlantic enclosing the Strait of Gibraltar and Mediterranean Outflow. Inverse methods were used to determine the velocity field from which volume transports and salt fluxes were calculated. The main northward flow of MW across 41°N occurs east of 12°W, at depths of 500 to 1500 m, and transports 50 to 75% of the MW. An advective westward pathway across 20°W transports MW at similar depths into the ocean interior between 35°N and 40°N. Insignificant salt fluxes across the southern section (24°N) at MW depths confirm that no MW crosses the southern Med Box boundary. The net overturning circulation of the Med Box, with inflowing surface waters and outflowing intermediate waters, is attributed both to the exchange at the Strait of Gibraltar and also to water mass transformation associated with entrainment of North Atlantic Water into the Mediterranean Outflow. The magnitude of the circulation provides an estimate of this entrainment of 1.6 ± 0.6 Sv, within the Med Box boundaries. For comparison with these observational estimates, the model used is OCCAM, a level model from the Ocean Circulation and Climate Advance Modelling Project. The primary reason for choosing this model is that experiments have been undertaken with the Strait of Gibraltar both open and closed, enabling a new approach to the investigation of MW transport. MW is identified using the salinity difference between the two model experiments. Although the model circulation (in the open-Strait run) has a similar net overturning to the hydrography, different MW transport pathways are observed. A weak and variable northward pathway along the Iberian Peninsula and a strong southwestward flow from the Gulf of Cadiz result in a higher proportion of MW flowing westwards (61%) than northwards (39%). Seasonal variability is observed, with maximum westward flow in Autumn (70%) and minimum in Spring (50%). There is no evidence in the model that the northward boundary current provides a direct route for Mediterranean salt to reach the Nordic Seas.
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Brown, S. C. "Investigation into decadal scale variability in the North Atlantic Ocean." Thesis, University of Edinburgh, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642087.
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The subsurface density of the North Atlantic displays considerable variability on decadal timescales. In this thesis the variability is examined from two directions. First I show direct observations of oceanic Rossby waves, using historical subsurface temperature data in the North Atlantic. Previously, such waves have only been directly observed using satellite data. Subsurface temperature data are used to investigate westward propagating Rossby waves across the North Atlantic at 30.5°N to 34.5°N, during 1970-74 and 1993-97. The latter period is when high resolution satellite altimetry data are available for comparison. The comparison was very favourable, with observed phase speeds east of the mid-Atlantic ridge, 3.6 cm s-1 in the altimeter data and 3.4 cm s-1 for the corresponding period in the hydrographic data. The phase speed of Rossby waves (west of the mid-Atlantic ridge) was observed to be 6.1 cm s-1 in 1970-74, compared with 4.3 cm s-1 in 1993-00. Interannual variability of the phase speed was also observed in the altimeter data, this variability was greater in the west than the east. Data from a coupled climate model (HadCM3) are used to assess the ability of an assimilation scheme, based on temperature-salinity preservation, to represent salinity given temperature data. The assimilation scheme was amended to account for meridional frontal movements. The adjustment improves the pre-assimilated salinity in comparison to the true-salinity in all areas south of 55°N, in the North Atlantic. Finally initial condition experiments are performed to determine the predictability of sea surface temperature (SST) and heat flux. The temperature and salinity fields resulting from the assimilation scheme are used as initial conditions in a twin experiment of HadCM3. When the temperature and salinity of the initial ocean state are perfectly known, the SST anomaly forecast skill is up to 5 years. When the assimilation scheme is used to provide these initial conditions for a forecast, the skill of predicting the SST anomaly is almost 2 years. There was no skill in predicting the fluxes in HadCM3 on a seasonal or annual timescale. However the average winter flux anomaly, when averaged over 5 years was found to be predictable.
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Harle, James. "Interannual-to-seasonal variability of the subpolar North Atlantic Ocean." Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418036.
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Brown, Susan C. "Investigations into decadal scale variability in the North Atlantic Ocean." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/13069.
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Mosedale, Timothy James. "North Atlantic Ocean-atmosphere interaction using simple and complex models." Thesis, University of Reading, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430918.
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Mohamed, Khairul Nizam. "Iron speciation study in the high latitude North Atlantic Ocean." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/336397/.
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Salter, Ian. "Particle fluxes in the North-East Atlantic and Southern Ocean." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/145313/.
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Concerns regarding the climatic implications of the increase in atmospheric CO2 concentrations throughout the anthropocene have provided the impetus to obtain a mechanistic understanding of oceanic processes and their role in regulating atmospheric pCO2. One important mechanism is the functioning of the biological pump which partitions carbon between the atmosphere and ocean reservoirs over relevant time scales. Current uncertainties revolve around the accuracy of upper ocean particle flux measurements, and the effect of iron and ballast minerals on the strength and efficiency of the biological carbon pump. This study documents the design and deployment of a neutrally buoyant sediment trap (PELAGRA). In the north-east Atlantic organic carbon fluxes were measured using this new technology and compared to indirect estimates of export based on 234Th and nutrient budgets. The vertical fluxes of 234Th into the traps were less than those estimated from the 234Th water column budget, which is interpreted to be the result of previous export events removing 234Th from the water column and the lateral advection of gradients of total 234Th/238U disequilibria confounding the Eulerian budgeting approach adopted. Successful simultaneous deployments in July 2006 at different depths provided a direct measurement of the attenuation of flux with depth, which at 1.8 is substantially greater than the canonical value of 0.856. PELAGRA deployments in the Southern Ocean were conducted as part of the CROZEX project, which examined the role of iron supply on bloom dynamics and subsequent export. Using a mass balance approach to account for the seasonal depletion of dissolved silica acid in surface waters and Si fluxes from the euphotic zone, potential surface export(100m) of organic carbon from +Fe bloom area was estimated to be in the order of 11-15 g C m-2, which is higher than previous estimates obtained from artificial fertilisation experiments. The issue of temporal decoupling between production and export processes was addressed by employing retrospective estimates of production. Particle export efficiency in the +Fe region to the north of the plateau (25-70%) was higher than similar estimates in the –Fe region (11-20%). Diatom size was well correlated with a range of calculated export ratios(100m). The main diatoms involved in the export from the surface were E. Antarctica in the +Fe region and F. kerguelensis in the –Fe region. E. Antarctica fluxes also dominated deep-water (3000m) diatom fluxes in the +Fe region, and its importance is attributed to the regions proximity to the Crozet Islands, where resting spores and dissolved iron are advected into the bloom area during the winter. Deep-water carbon fluxes measured to the south of the plateau. Deep-water carbon fluxes measured south of the plateau (0.09 g C m-2 yr-1) are consistent with previous measurements in a similar environment. In the +Fe region to the north, deep water fluxes were 0.4 g C m-2 yr-1 indicating that natural iron fertilisation can increase the strength of the biological carbon pump by a factor of 4. Comparison of fluxes with satellite-derived productivity also suggests that the efficiency of the biological pump in transferring organic carbon to the deep-ocean is increased by a factor of 3 in the presence of iron. The flux and composition of amino acids, in relation to the dominant mineral phases that comprised the particulate flux in the NE Atlantic and the Southern Ocean was also examined. The fraction of carbon that could be accounted for by the total hydrolysable amino acids varied very little (20-30%) with sample composition. Protein amino acids were used to quantify the degradation state of the settling particulate material. Specific amino acids seem to infer diatomaceous rather than calcareous as the dominant organic matter source. Multiple linear regression analysis reveals that mineral fluxes can only explain a very small amount of the variability in amino acid composition, which does not support previous hypotheses that relate mineral fluxes and organic carbon fluxes through the differential protective capacity of various mineral phases.
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Barciela, FernaÌndez Rosa MariÌa. "Modelling ecosystem dynamics in the turblent surface layers of the ocean." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252437.
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Porter, Marie. "Linking of the surface North Atlantic Ocean to adjacent terrestrial ice masses." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=195922.
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Powell, A. D. J. "Palaeobathymetric analysis of tertiary sediments in the northern North Sea and north-east North Atlantic Ocean." Thesis, University of Exeter, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381310.
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Edmonds, Henrietta N. (Henrietta Nash). "Tracer applications of anthropogenic iodine-129 in the North Atlantic Ocean." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/53525.
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Lerner, Paul (Paul Edmund). "Scavenging and transport of thorium radioisotopes in the North Atlantic Ocean." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119989.
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Thesis: 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), 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 321-351).
Many chemical constituents are removed from the ocean by attachment to settling particles, a process referred to as "scavenging." Radioisotopes of thorium, a highly particle-reactive element, have been used extensively to study scavenging in the ocean. However, this process is complicated by the highly variable chemical composition and concentration of particles in oceanic waters. This thesis focuses on understanding the cycling of thorium as affected by particle concentration and particle composition in the North Atlantic. This objective is addressed using (i) the distributions 228,230,234 Th, their radioactive parents, particle composition, and bulk particle concentration, as measured or estimated along the GEOTRACES North Atlantic Transect (GA03) and (ii) a model for the reversible exchange of thorium with particles. Model parameters are either estimated by inversion (chapter 2-4), or prescribed in order to simulate 230Th in a circulation model (chapter 5). The major findings of this thesis follow. In chapters 2 and 3, I find that the rate parameters of the reversible exchange model show systematic variations along GA03. In particular, k1 , the apparent first-order rate "constant" of Th adsorption onto particles, generally presents maxima in the mesopelagic zone and minima below. A positive correlation between k, and bulk particle concentration is found, consistent with the notion that the specific rate at which a metal in solution attaches to particles increases with the number of surface sites available for adsorption. In chapter 4, I show that Mn (oxyhydr)oxides and biogenic particles most strongly influence k1 west of the Mauritanian upwelling, but that biogenic particles dominate ki in this region. In chapter 5, I find that dissolved 230Th data are best represented by a model that assumes enhanced values of k, near the seafloor. Collectively, my findings suggest that spatial variations in Th radioisotope activities observed in the North Atlantic reflect at least partly variations in the rate at which Th is removed from the water column.
by Paul Lerner.
Ph. D.
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Bloxsom, Peter G. "North Atlantic ocean circulation and the onset of Northern Hemisphere glaciation." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/73539/.
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Since the early Cenozoic, the Earth’s climate has been gradually cooling. Large ice sheets have expanded on several occasions in the past 5000 kyr (50 Ma), with the last major expansion being the onset of major ice sheets in the Northern Hemisphere between 3600 and 2500 ka. This period was characterised by a prolonged increase in ice volume, modulated by orbital forcing. At the same time, major tectonic changes were taking place, with the closure of the Central American Seaway most significant. This thesis aims to address the issue of what caused the onset of major Northern Hemisphere glaciation through an in depth study of samples from North Atlantic ODP Site 982 (57° 31’ N, 15° 51’ W; 1145 m water depth). Multi-species benthic foraminifera composite trace metal records (Mg/Ca, B/Ca, Li/Ca, Cd/Ca) were produced, and the composite Mg/Ca record was used to develop a new regional temperature calibration for the Pliocene. Paleoceanographic records of bottom water temperature and saturation state were produced, as well as bottom water flow speed records using the Sortable Silt (SS) proxy. Bottom water temperature (BWT) records showed an abrupt, ~2°C cooling at 2800-2700 ka, consistent with other previously published records. These data are combined with previously published benthic stable isotope (δ18Ob) records to reconstruct seawater oxygen isotope reconstructions (δ18Osw) across the period of study, and this is found to predominately reflect changes in global ice volume. A major and prolonged increase in ice volume (3500-3000 ka) is identified, equivalent to up to ~55m sea level decrease. The response of the North Atlantic region to this ice sheet growth was tested using previously published sea surface temperature (SST) and δ18Ob records from ODP Site 982, in addition to the new record from this study. The ice volume was found to have influenced the response of SST, δ18Ob, and SS to orbital forcing from changing insolation. Prior to the ice sheet growth, bottom water flow speed varied proportionally with sea surface temperatures, with increased deep water formation during periods of high seasonality. The growing ice sheets responded more slowly to insolation changes, and the presence of this ice sheet increased deep water formation by further cooling saline surface waters. This resulted in feedback loops that intensified deep water flow, leading to a significant increase in North Atlantic Deep water penetration to the southern ocean. A major decrease in δ18Osw at 2800-2700 ka was interpreted as either a loss of Antarctic ice mass, or a reorganization of North Atlantic water masses. Comparison of ice volume records with orbital spectra and reconstructions of the closure of the Central American Seaway suggest the immediate cause of Northern Hemisphere glaciation was a period of orbital conditions favourable to ice sheet growth. Another underlying cause was a series of tectonic shifts, including the closure of the Central American Seaway from 4200 ka, which changed heat and moisture transport patterns to the high latitudes.
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Dentico, Carlotta <1993>. "OCEAN DYNAMICS IN THE SUBPOLAR NORTH ATLANTIC IN A CLIMATE SIMULATION." Master's Degree Thesis, Università Ca' Foscari Venezia, 2019. http://hdl.handle.net/10579/14274.
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The Subpolar Gyre (SPG) is a dominant oceanic feature of the upper circulation in the Northwest Atlantic Ocean, characterized by a cyclonic circulation pattern. It is a critical component of the Earth’s climatic system, as it modulates the exchange of heat, salt, fresh water and sea ice between the North and Tropical Atlantic and Arctic Ocean, and it interacts with large-scale oceanic features like the Atlantic Meridional Overturning Circulation and the Global Thermohaline Circulation.
Currently, the SPG variability is thought to be largely controlled by an east-west seawater density gradient in the SPG region that is determined by the contrast between hot and salty water masses from mid-latitude Atlantic Ocean, mainly transported by the Gulf Current, and fresh and cold water masses from the Arctic Ocean.
In this thesis, I investigate ocean dynamics in the SPG region, using a state-of-the-art global ocean – regional atmosphere coupled model. The goal of this research is to determine how ocean-atmosphere coupling affects the general mechanism of SPG variability in this state-of-the-art model. To this purpose, I focus on interannual and decadal changes in the strength of the SPG, identified by variations in the mass barotropic streamfunction. The main analysis uses an ensemble of three simulations with ocean-atmosphere coupling activated in the SPG basin and Arctic region and differing for the resolution of the atmospheric model. Secondly, I compared these simulations to an additional simulation where the ocean-atmosphere coupling is activated in the tropical Atlantic instead of in the SPG/Arctic to disentangle different contributions to SPG dynamics, specifically those regarding heat and salt input from the Tropical Atlantic and fresh water fluxes and sea ice export from the Arctic. At the end I also evaluate the linkages between SPG and the Atlantic Meridional Overturning Circulation (AMOC), especially their relationship with meridional ocean transport of heat and mass.
The investigation makes use of statistical methods to identify lead-lag relationships between the SPG strength and selected driving variables as triggers of the described variability (sea surface temperature, salinity and density, anomalies of sea ice thickness and fraction, fresh water fluxes) and heat and mass transport in the AMOC. Methods include also time series analysis, cross-correlation and linear regression analysis, composite analysis and wavelet analysis.
A first key aspect of the research is the identification recurrent features of SPG variability in the three simulations to determine whether the SPG variability is due to internal variability (differences between simulations) or to external forces (consistent behavior). The study of consistent cross-correlation spatial patterns describing the relationship between SPG strength and the driving variables allows to unveil sources and pathways of SPG variability. Comparison between the simulations will reveal potential effects of model resolution. Finally, the analysis of time series will describe the connection between the AMOC, identified by changes in heat and mass transport, and SPG strength.
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Thomas, A. R. "Glacial-interglacial variations in the geochemistry of North Atlantic deep-sea sediments." Thesis, University of Liverpool, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382148.
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Agarwal, Atul. "Long-term analysis of the wave climate in the North East Atlantic and North Sea." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10467.
Full textAbstract:
Changes in the marine environment have been reported for over three decades in terms of mean annual wave heights, exceedance probabilities and extreme conditions. More recently, the existence of a link between these changes and anthropogenic climate change has been postulated. This is not unreasonable, as climatic changes in regional warming and cooling are likely to alter wind patterns, and therefore the wave climate as well. In an attempt to mitigate climate change and increase energy security, the offshore environment is being looked at to provide sustainable energy from wind, waves and tides. As a result the number of marine structures is only likely to increase. While survivability in this environment is essential for all such installations, some devices such as wave energy converters also rely on the environment for energy production. In designing these offshore structures to survive the harshest conditions as well as to ensure optimum operation, knowledge of the evolution of the wave climate is essential. This study aims to identify and evaluate any historical trends that may be exhibited by the wave climate in the North East Atlantic and North Sea region. The study also aims to investigate the link between any observed changes and atmospheric greenhouse gas levels and projected wave conditions for the 21st century. This is achieved by producing a long-term, high resolution hindcast of wave conditions for 1871-2010 using the third-generation spectral wave model WAVEWATCH III. A dataset of wave climate projections for the high, medium and low emissions scenarios is also prepared by forcing the model with GCM winds for 2001-2100. In addition to dynamically projecting the wave climate in the 21st century for different IPCC climate change scenarios, statistical methods were applied to historic data to estimate extreme events in terms of 100-year return values of significant wave height. These, together, provide some idea of the plausible wave climate up to 2100. The results of the work show the existence of long-term trends in the historical wave climate in the region from 1921 onwards. However, based on the findings of the study, it is unlikely that these are a result of changes in atmospheric greenhouse gas concentrations and are more likely due to internal variability in the system.
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Gladman, Graham Jeffrey. "The role of ocean-atmosphere interactions in the thermal variability of the upper North Atlantic ocean." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369540.
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Wadsworth, Emilie R. "The identification and characterisation of the North Atlantic Heinrich Events using environmental magnetic techniques." Thesis, University of St Andrews, 2006. http://hdl.handle.net/10023/2782.
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Heinrich Events (HEs) define intervals of major ice rafting from the Laurentide Ice Sheet (LIS) into the North Atlantic during that last glacial period. The discovery of potential European-sourced precursors to HEs suggest that the smaller, but climactically sensitive, European ice sheets (EIS) may have played a role in the triggering of HEs and their impact on global climates. Environmental magnetism has proved itself to be a useful, rapid and non-destructive tool in the identification and quantification of provenance in sediments from various depositional environments. In this work, environmental magnetic analyses are applied to marine sediment records from the European margin of the NE Atlantic and known to contain ice-rafted debris (IRD) from both LIS and EIS sources. The primary aim in the work of this thesis is to evaluate the methodology as a means of distinguishing IRD provenance. From the data obtained here it is possible to identify several magnetic events that correspond to the HEs and other layers of detrital material and which correlate well to previous standard petrological analyses performed on the same core materials. Magnetic signatures differ within the HEs, suggesting a changing balance of input from multiple sources as opposed to a single LIS source. The data suggest a phasing of these compositional differences through individual HEs. The potential of using environmental magnetic techniques in the identification of IRD provenance within marine sediments is discussed, as is the significance of the observed provenance variations within the cores studied.
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Brown, Catherine Alicia. "Oscillatory behavior in an ocean general circulation model of the North Atlantic." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0004/MQ46006.pdf.
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Silverthorne, Katherine E. "Near-inertial and thermal to atmospheric forcing in the North Atlantic Ocean." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59756.
Full textAbstract:
Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 127-133).
Observational and modeling techniques are employed to investigate the thermal and inertial upper ocean response to wind and buoyancy forcing in the North Atlantic Ocean. First, the seasonal kinetic energy variability of near-inertial motions observed with a moored profiler is described. Observed wintertime enhancement and surface intensification of near-inertial kinetic energy support previous work suggesting that near-inertial motions are predominantly driven by surface forcing. The wind energy input into surface ocean near-inertial motions is estimated using the Price-Weller- Pinkel (PWP) one-dimensional mixed layer model. A localized depth-integrated model consisting of a wind forcing term and a dissipation parameterization is developed and shown to have skill capturing the seasonal cycle and order of magnitude of the near-inertial kinetic energy. Focusing in on wintertime storm passage, velocity and density records from drifting profiling floats (EM-APEX) and a meteorological spar buoy/tethered profiler system (ASIS/FILIS) deployed in the Gulf Stream in February 2007 as part of the CLIvar MOde water Dynamics Experiment (CLIMODE) were analyzed. Despite large surface heat loss during cold air outbreaks and the drifting nature of the instruments, changes in the upper ocean heat content were found in a mixed layer heat balance to be controlled primarily by the relative advection of temperature associated with the strong vertical shear of the Gulf Stream. Velocity records from the Gulf Stream exhibited energetic near-inertial oscillations with frequency that was shifted below the local resting inertial frequency. This depression of frequency was linked to the presence of the negative vorticity of the background horizontal current shear, implying the potential for near-inertial wave trapping in the Gulf Stream region through the mechanism described by Kunze and Sanford (1984). Three-dimensional PWP model simulations show evidence of near-inertial wave trapping in the Gulf Stream jet, and are used to quantify the resulting mixing and the effect on the stratification in the Eighteen Degree Water formation region.
by Katherine E. Silverthorne
Ph.D.
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Krijnen, Justin. "Key mechanisms of surface water pCO2 variability in the North Atlantic Ocean." Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/47402/.
Full textAbstract:
A proxy for the North Atlantic gyre circulation has been developed, using sea-surface height from altimetry. In conjunction with the winter North Atlantic Oscillation (NAO) index, statistical analysis has been applied to understand the key mechanisms of surface water partial pressure of CO2 (pCO2) variability, both on the seasonal and inter-annual timescale. With respect to the seasonal amplitude of surface pCO2 in temperate regions (>40°N), it is found that the gyre circulation strength, in response to the winter NAO index, drives this seasonal amplitude. Under positive NAO index winters, the formation of mode waters is favoured through strong surface cooling. This deepens the mixed layer, entraining carbon and nutrient-rich subsurface waters into the surface layer and increasing the surface pCO2 in winter. This deep winter mixing, bringing up nutrients in combination with enhanced advection of nutrients from the subpolar region, may also enhance and prolong the following spring bloom, decreasing the pCO2 in both spring and early summer. Thus, the seasonal amplitude of surface pCO2 under a positive NAO phase would increase. Under negative NAO winters, surface cooling is not as pronounced compared to a positive NAO winter and therefore the mixed layer is not as deep. Thus, both vertical and horizontal (via advection) carbon and nutrient entrainment are reduced thereby decreasing the pCO2 in winter and potentially weakening the following spring bloom. Thus the seasonal amplitude of surface pCO2 under a negative NAO phase would decrease. The subtropical regions (25 - 40°N) are also subjected to similar processes as the temperate regions, under both positive and negative NAO winters. However, the above-mentioned lagged effect of carbon-rich sub-surface water and nutrient entrainment in winter on the intensity of the spring bloom has to be treated with caution given the lack of statistically significant correlations between the surface pCO2 in winter and the proxy for carbon-rich subsurface water in spring. On inter-annual timescales, the phase of the winter NAO alters the ocean circulation in all regions. Under a positive NAO index, the subtropical gyre is more spun-up and with increased SST, increasing the annual mean pCO2. In the temperate zone, the interplay between carbon entrainment and biological drawdown dominates, dampening the inter-annual pCO2 variability.
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Manning, Jane Elizabeth. "Patterns of spatial variation : bacteria and tintinnids in the North Atlantic ocean." Thesis, Swansea University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678684.
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Pan, Jianfu. "Energy cycles in the summer tropical atmosphere over the North Atlantic Ocean /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487757723995282.
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Payne, Brian J. "Fishing the Borderlands: Government Policy and Fishermen on the North Atlantic." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/PayneBJ2001.pdf.
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Wolfteich, Carl Martin. "Satellite-derived sea surface temperature, mesoscale variability, and foraminiferal production in the North Atlantic." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17355.
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Dong, Shenfu. "Interannual variations in upper ocean heat content and heat transport convergence in the western North Atlantic /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/11021.
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Williams, Catherine E. "The circulation and fluxes from the Arctic into the North Atlantic Ocean 1979-2002 model results." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FWilliams.pdf.
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Thesis (M.S. in Applied Science (Physical Oceanography))--Naval Postgraduate School, Sept. 2004.Thesis Advisor(s): Wieslaw Maslowski. Includes bibliographical references (p. 87-90). Also available online.
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Sklut, Micah. "Investigating SST influence on the North Atlantic Oscillation using the NCAR community atmospheric model." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 5.62Mb, 121 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/1428196.
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Fan, Meizhu. "Low frequency North Atlantic SST variability weather noise forcing and coupled response /." Fairfax, VA : George Mason University, 2008. http://hdl.handle.net/1920/3421.
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Thesis (Ph.D.)--George Mason University, 2008.Vita: p. 190. Thesis director: Edwin K. Schneider. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Climate Dynamics. Title from PDF t.p. (viewed Mar. 9, 2009). Includes bibliographical references (p. 181-189). Also issued in print.
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Goodman, Paul Joseph. "The role of North Atlantic Deep Water formation in the thermohaline circulation /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10025.
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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.
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Mosher, Celeste V. "Commensalism and Reproductive Biology of the Brittle Star Ophiocreas oedipus Associated with the Octoral Metallogorgia melanotrichos on the New England Corner Rise Seamounts." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/MosherCV2008.pdf.
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Zhang, Meng. "Satellite observations and numerical simulations of jet-front gravity waves over North America and North Atlantic Ocean." Texas A&M University, 2008. http://hdl.handle.net/1969.1/85995.
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In this study, a month-long simulation of gravity waves over North America and
North Atlantic Ocean is performed using the mesoscale model MM5 for January 2003,
verified with Advanced Microwave Sounding Unit-A (AMSU-A) radiance observations
in the upper troposphere and lower stratosphere. According to the monthly mean
statistics, four regions of strong gravity wave activities are found both in the simulation
and the AMSU-A observations: northwestern Atlantic, Appalachian Mountains, Rocky
Mountains and Greenland, respectively. Those over the northwestern Atlantic Ocean are
strongly associated with the midlatitude baroclinic jet-front systems, while the other
three regions are apparently collocated with high topography.
Imbalance diagnosis and numerical sensitivity experiments of a strong gravity
wave event during January 18-22 show that the gravity waves are strongly linked to the
unbalanced flow in the baroclinic jet-front system. The gravity waves are usually
radiated from the upper tropospheric jet exit region with maximum nonlinear balance
equation residual ( Δ NBE; key indicator of flow imbalance), distinctly different from other surface sources. Flow imbalance related strongly to tropopause folding and
frontogenesis of the large-scale background flow. Similar wave characteristics are
simulated in experiments with different microphysics and grid resolutions. The Δ NBE is
again shown to be a good predictor for jet-front related gravity waves, suggesting its
potential application to gravity wave parameterizations for global and climate models.
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Braun, Camrin Donald. "Movements and oceanographic associations of large pelagic fishes in the North Atlantic Ocean." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119992.
Full textAbstract:
Thesis: Ph. D., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2018.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 138-154).
Highly migratory marine fishes support valuable commercial fisheries worldwide. Yet, many target species have proven difficult to study due to long-distance migrations and regular deep diving. Despite the dominance of oceanographic features, such as fronts and eddies, in the open ocean, the biophysical interactions occurring at the oceanic (sub)mesoscale (< 100 km) remain poorly understood. This leads to a paucity of knowledge on oceanographic associations of pelagic fishes and hinders management efforts. With ever-improving oceanographic datasets and modeling outputs, we can leverage these tools both to derive better estimates of animal movements and to quantify fish-environment interactions. In this thesis, I developed analytical tools to characterize the biophysical interactions influencing animal behavior and species' ecology in the open ocean. A novel, observation-based likelihood framework was combined with a Bayesian state-space model to improve geolocation estimates for archival-tagged fishes using oceanographic profile data. Using this approach, I constructed track estimates for a large basking shark tag dataset using a high-resolution oceanographic model and discovered a wide range of movement strategies. I also applied this modeling approach to track archival-tagged swordfish, which revealed affinity for thermal front and eddy habitats throughout the North Atlantic that was further corroborated by synthesizing these results with a fisheries-dependent conventional tag dataset. An additive modeling approach applied to longline catch-per-unit effort data further highlighted the biophysical interactions that characterize variability in swordfish catch. In the final chapter, I designed a synergistic analysis of high-resolution, 3D shark movements and satellite observations to quantify the influence of mesoscale oceanography on blue shark movements and behavior. This work demonstrated the importance of eddies in structuring the pelagic ocean by influencing the movements of an apex predator and governing the connectivity between deep scattering layer communities and deep-diving, epipelagic predators. Together, these studies demonstrate the breadth and depth of information that can be garnered through the integration of traditional animal tagging and oceanographic research with cutting-edge analytical approaches and high-resolution oceanographic model and remote sensing datasets, the product of which provides a transformative view of the biophysical interactions occurring in and governing the structure of the pelagic ocean.
by Camrin Donald Braun.
Ph. D.
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Grey, Stephen M. "Analysis and assimilation of temperature and altimetry data in the North Atlantic Ocean." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/13954.
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Observations of subsurface temperatures in the North Atlantic between 1950 and 1994 have been analysed to investigate interdecadal variability. Previous studies have concentrated on the more plentiful sea surface temperature data or on limited hydrographic data. Here, all subsurface temperature data, principally from bathythermographs, are used to investigate the development and evolution of temperature anomalies. During most of the period, a dipole feature was seen. The western subtropical gyre and the ocean north of 50°N were occupied by anomalies of opposite sign. These regions appear to show a cycle of warming and cooling with a period of approximately 30 years but the data record is too short to determine whether this is a regular oscillation. There is evidence of propagation of temperature anomalies along the paths of the major upper ocean currents, namely along the Gulf Stream and North Atlantic Current and also along the return currents on the southern edge of the subtropical gyre. An intense warm anomaly on the northern edge of the subtropical gyre developed between 1988 and the end of the data in 1994. The Gulf Stream front became steeper and isotherms were depressed by up to 150m. This is consistent with a stronger Gulf Stream and an intensification of the circulation of the subtropical gyre. This is compared with a cold anomaly in 1966-1972 which is opposite in nature, indicating a weaker subtropical gyre circulation. A scheme developed by Cooper and Haines (1996) has been employed to assimilate sea level anomaly data from the TOPEX/POSEIDON altimeter with a climatological hydrography of the North Atlantic.
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Dumousseaud, Cynthia. "Physical and biological forcings on the carbonate chemistry in the North Atlantic Ocean." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/168949/.
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The atmospheric concentration of CO2 has risen considerably since the industrial revolution, and the subsequent uptake of atmospheric CO2 by the oceans has affected the carbonate system and caused a reduction in the pH of the oceans. Model estimates involving future CO2 emission scenarios have predicted a significant increase of oceanic Dissolved Inorganic Carbon concentrations by the end of the century, corresponding to a decrease in oceanic pH by up to 0.4. In order to observe and predict changes in primary productivity and community structure in the oceans associated with future climate change, precise measurements of all the carbonate system parameters are important. The natural processes affecting the seasonal and regional variations of the carbonate chemistry are still poorly understood and sustained monitoring programs are required in order to determine the importance of hydrographical and biogeochemical forcings. The relationships between physical and biological parameters and carbonate system parameters were investigated in several regions of the North Atlantic Ocean, allowing a better understanding of the natural processes affecting the carbonate system in this ocean basin. For this purpose, the seasonal and inter-annual variability of the carbonate system in the Northeast Atlantic Ocean was studied through a ship of opportunity program, allowing observations of the short-term processes affecting the carbonate system and air-sea CO2 fluxes. The results showed contrasting effects of winter mixing and sea surface temperature on the carbonate system and the air-sea CO2 fluxes. In addition, the distributions of the carbonate system parameters were determined in the Iceland Basin and in the sub-tropical Northeast Atlantic Ocean. The carbonate system in the Iceland Basin was characterized by mesoscale variability associated to the presence and development of an eddy dipole in the study region; while the sub-tropical Northeast Atlantic Ocean showed spatial variability in all the chemical parameters, associated with coastal upwelling and remineralization in an oxygen minimum zone. Although the physics appeared to be the main forcing on the carbonate system in this study, the role of biology in the seasonality of the carbonate system is highly important. However, physical forcings tend to set the level for biological drawdown and therefore highly contribute to the variability of the carbonate system and CO2 fluxes.
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Payne, Brian Joseph. "Fishing a Borderless Sea: Environmental Territorialism in the North Atlantic, 1818-1910." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/PayneBJ2006.pdf.
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