Dissertations / Theses on the topic 'Sea ice'
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1
Gray, J. M. N. T. "Sea ice dynamics." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240183.
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Babb, David. "Sea ice motion within the Beaufort Sea." American Geophysical Union, 2013. http://hdl.handle.net/1993/23694.
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Sea ice drift and associated forcing mechanisms within the Beaufort Sea are examined within the context of a mechanically weakening Arctic ice pack. Extensive in situ observations of ice drift, ice mass balance and surface winds are supplemented by remotely sensed and modeled data to analyse the forcing of sea ice motion. First we analyse the anomalous export of 13.4 x 103 km2 of sea ice through the Bering Strait during winter 2011-2012. The event highlights a tendency towards increased ice transport through the Bering Strait since 2008 as a result of climate induced weakening of the arctic ice pack. Secondly, as part of the Beaufort Regional Environmental Assessment we analyse the seasonal evolution of ice drift in the Beaufort Sea during Spring as the ice pack transitions from mechanically strong conditions in late winter to weak summer conditions that foster free drift and thus increased ice drift speeds.
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Wilkinson, Jeremy. "Sea ice, convection and the Greenland Sea." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/25132/.
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The region where deep open-ocean convection occurs in the Greenland Sea corresponds to that where a sea ice winter feature, the Odden, usually forms. The role of sea ice in modifying the surface waters to overturn to depth is evaluated through the combination of in siu measurements, satellite imagery, meteorological measurements and drifting buoy data. Results suggest local meteorological and oceanographic conditions govern the ice conditions over the region. The high ambient wave energy precludes the formation of ice beyond the frazil-pancake stage; the changing surface pressure field, due to passing storm systems, influences the daily shape and extent of the Odden and enables pancake ice to expel brine at an increased rate. Finally, the analysis of drifting buoy data reveal that the ice is in free drift. t These characteristics suggests the Odden may be regarded as a large scale latent heat polynya, with the predominately northerly winds blowing newly formed sea-ice constantly southward such that it melts in a different area from that of its formation. This salt separation process whereby the majority of brine is deposited where the ice was formed, and a smaller amount being released, through brine drainage, as the ice drifts with the prevailing wind has important consequences for the spatial and temporal distribution of the salt flux and hence surrounding hydrography. This is clearly demonstrated through the development of a salt flux model, which involves brine drainage and drift. A simple one-dimensional mixed layer model, driven by results of the salt flux model, predicts a strong density enhancement and deepening of the mixed layer over time. It is therefore envisaged that the formation of sea ice, brine drainage and drift are fundamental in eroding the pycnocline between the surface waters and those below. Sea ice should therefore be viewed as a preconditioning activity to deep overturning of the waters of the central Greenland Sea.
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Von, Eye Maxine Jutta Erika. "Sea ice and convection in the Greenland Sea." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648527.
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Lipscomb, William H. "Modeling the thickness distribution of Arctic sea ice /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/10081.
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Light, Bonnie. "Structural-optical relationships in first-year sea ice /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/10079.
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Lemcke, Mary D. "The sensitivity of CSIM5 sea-ice simulations to atmospheric state variables." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 156 p, 2009. http://proquest.umi.com/pqdweb?did=1886744831&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Heacock, Tony. "Sea ice -- Nunavut -- Barrow Strait." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=105370.
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Cheng, Bin. "On the modelling of sea ice thermodynamics and air-ice coupling in the Bohai Sea and the Baltic Sea." Helsinki : Finnish Institute of Marine Research, 2002. http://ethesis.helsinki.fi/julkaisut/mat/fysik/vk/cheng/.
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Brigham, Lawson Walter. "Sea ice variability in Russian Arctic coastal seas : influences on the northern sea route." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621873.
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Hendry, K. R. "Behaviour of trace metals in sea-ice brine and microalgae: reconstructing the Antarctic sea-ice environment." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491532.
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The extent of sea-ice and its interactions with biological and physical processes in the Southern Ocean play a key role in regulating atmospheric greenhouse gases, such as carbon dioxide, over glacial-interglacial timescales. Understanding how sea-ice influences these processes is essential for our understanding of recent climate change and for modelling of future climates. Much of our insight into past climates originates from the use of geochemical proxies, which relate to environmental parameters such· as temperature, salinity, pH and carbonate chemistry. The stable isotope and trace metal compositions of foraminiferal calcite are widely used, and of diatom opal to a lesser extent, as palaeothermometers and palaeonutrient indicators. However, these geochemical proxies are complex and exhibit multiple controls, resulting in apparently conflicting interpretations. In particular, we need to improve our understanding of the influence of sea-ice and low temperatures on these microalgae. The objective of this thesis is to investigate the impact of seasonal sea-ice on trace metals and geochemical proxies as part of a larger, three year field campaign of water and sediment sampling off the West Antarctic Peninsula. This thesis demonstrates tl1e key roles played by the Southern Ocean sea-ice environment in the availability of trace metals over a range of timescales. On a seasonal timescale, changes in populations during the intense high latitude summer blooms influence algal trace metal requirements and uptake. On annual and interannual timescales, sea-ice influences stable isotop.e and trace metal uptake by foraminifera and diatoms. Finally, processes within meltwater zones significantly influence past nutrient and freshwater budgets from centennial to glacial-interglacial timescales.
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Rees, Jones David. "The convective desalination of sea ice." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/246582.
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This thesis aims to improve our understanding of the fundamental processes affecting the growth of sea ice in the polar oceans in order to improve climate models. Newly formed sea ice contains a significant amount of salt as liquid brine in the interstices of an ice matrix. My focus is on one of the processes by which the salt content of sea ice decreases, namely convective desalination, which is also often called gravity drainage by geophysicists. Modelling convective desalination requires an understanding not only of the thermo-dynamics of sea-ice growth but also of its internal fluid dynamics. This thesis considers a class of physical systems called mushy layers, of which sea ice is an example. Mushy layers are multi-component systems consisting of a porous matrix of solid phase whose interstices contain the same substance in the liquid phase. I develop a mathematical description of these systems in terms the of mushy-layer equations and explore the appropriate boundary conditions at a mush-liquid interface. I develop a simple Chimney-Active-Passive (CAP) model of convection in mushy layers for arrays of liquid chimneys in two and three dimensions. This allows the interstitial fluid flow and salt flux from the mushy layer to be determined in terms of the dimensionless parameters of the system. I discuss important mathematical and physical aspects of the CAP model. I then explain the physics of gravity drainage from sea ice, elucidating the connection between downward flow through liquid brine channels (chimneys) and a convective upwelling in the rest of the ice that is sustained by horizontal density differences and provides the fluid to replace that which drains from the ice. I use the CAP model to determine the convective upwelling velocity mathematically, deriving a new, physical parameterization of gravity drainage. I test my predictions by investigating previous laboratory observations of the propagation of dye fronts. Finally, I take a one-dimensional, thermodynamic sea-ice model of the kind currently used in coupled climate models and parameterize convective desalination using the CAP model. The parameterization allows determination of physical properties and salt fluxes from sea ice dynamically, corresponding to the calculated, evolving salinity of the sea ice, in contrast to older, established models that prescribe a fixed salinity. I find substantial differences compared to previous models, particularly in terms of predicted salt fluxes from sea ice. I explain the likely implications and potential advantages of my parameterization for climate models.
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Farrell, S. L. "Satellite laser altimetry over sea ice." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1445477/.
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The Arctic region plays an important role in the global climate system through various feedbacks, involving surface albedo, oceanic deep-water formation, and sea surface salinity, which can amplify climate variability and change. We investigate the exploitation of data collected by the first Earth-orbiting laser altimeter carried onboard ICESat over the sea-ice covered regions of the Arctic Ocean. We extract parameters associated with the study of the polar climate system including the time-varying component of sea surface topography and sea ice freeboard. We assess an existing method for the retrieval of Arctic sea surface height from ICESat data. We present an alternative method for sea surface height retrieval, based on surface reflectivity and analysis of parameters associated with the shape of the received echo. This method aims to discriminate echoes originating over leads or thin ice. We provide the first maps of Arctic sea surface height as derived from ICESat. We examine the accuracy of our results through comparisons with independent sea surface height estimates derived from ENVISAT radar altimetry. We demonstrate the use of sea surface height data for oceanographic and geodetic applications in the Arctic Ocean. We derive an ICESat mean sea surface which, when combined with the recently developed Arctic hybrid geoid model, can be used to analyse mean dynamic ocean topography. In addition we investigate the use of ICESat sea surface height measurements to map marine gravity anomalies up to the limit of coverage at 86 N. By combining ICESat surface elevation measurements with sea surface height estimates, we derive sea ice freeboard throughout the Arctic up to 86 N. We compare our results to coincident estimates of sea ice freeboard from ENVISAT. Finally, we explore the feasibility of combining satellite laser and radar altimetric measurements of sea ice freeboard to measure the depth of snow loading on sea ice.
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Gomez, Natalya Alissa. "On Sea Level - Ice Sheet Interactions." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11242.
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This thesis focuses on the physics of static sea-level changes following variations in the distribution of grounded ice and the influence of these changes on the stability and dynamics of marine ice sheets. Gravitational, deformational and rotational effects associated with changes in grounded ice mass lead to markedly non-uniform spatial patterns of sea-level change. I outline a revised theory for computing post-glacial sea-level predictions and discuss the dominant physical effects that contribute to the patterns of sea-level change associated with surface loading on different timescales. I show, in particular, that a large sea-level fall (rise) occurs in the vicinity of a retreating (advancing) ice sheet on both short and long timescales. I also present an application of the sea-level theory in which I predict the sea-level changes associated with a new model of North American ice sheet evolution and consider the implications of the results for efforts to establish the sources of Meltwater Pulse 1A. These results demonstrate that viscous deformational effects can influence the amplitude of sea-level changes observed at far-field sea-level sites, even when the time window being considered is relatively short (≤ 500 years).Earth and Planetary Sciences
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Laxon, Seymour William Clarke. "Satellite radar altimetry of sea ice." Thesis, University College London (University of London), 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325510.
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The thesis concerns the analysis and interpretation of data from satellite borne radar altimeters over ice covered ocean surfaces. The applications of radar altimetry are described in detail and consider monitoring global climate change, the role that sea ice plays in the climate system, operational applications and the extension of high precision surface elevation measurements into areas of sea ice. The general nature of sea ice cover is discussed and a list of requirements for sea ice monitoring is provided and the capability of different satellite sensors to satisfy needs is examined. The operation of satellite borne altimeter over non-ocean surfaces is discussed in detail. Theories of radar backscatter over sea ice are described and are used to predict the radar altimeter response to different types of sea ice cover. Methods employed for analysis of altimeter data over sea ice are also described. Data from the Seasat altimeter is examined on a regional and global scale and compared with sea ice climatology. Data from the Geosat altimeter is compared with co-incident imagery from the Advanced Very High Resolution Radiometer and also from airborne Synthetic Aperture Radar. Correlations are observed between the altimeter data and imagery for the ice edge position, zones within the ice cover, new ice and leads, vast floes and the fast ice boundary. An analysis of data collected by the Geosat altimeter over a period of more than two years is used to derive seasonal and inter-annual variations in the total Antarctic sea ice extent. In addition the retrieval of high accuracy elevation measurements over sea ice areas is carried out. These data are used to produce improved maps of sea surface topography over icecovered ocean and provide evidence of the ability of the altimeter to determine sea ice freeboard directly. In addition the changing freeboard of two giant Antarctic tabular icebergs, as measured by the Geosat altimeter, is presented. As a summary the achievements are reviewed and suggestions are made towards directions for further work on present data sets and for future data from the ERS-1 satellite.
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Reisemann, Matthias Heinrich. "Ultrasonic transmission properties of sea ice." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624200.
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Cottier, Finlo Robert. "Brine distribution in young sea ice." Thesis, University of Cambridge, 1999. https://www.repository.cam.ac.uk/handle/1810/273248.
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Tamura-Wicks, Helen. "Sensitivity study of Caspian sea ice." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/30644.
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The Northern Caspian lies along the southern-most boundary within the Northern Hemisphere where sea-ice forms. Although ice cover is typically observed between November and March, it experiences high spatio-temporal variabilities. This variability may be of interest in the long-term as it may act as an early indicator of large-scale climate change, as well as being an area of interest to industries and vulnerable species. Through empirical and model studies, this thesis carries out a sensitivity study of Caspian sea-ice for the first time. Caspian sea-ice concentration from satellite passive microwave data and surface daily air temperatures are analysed from 1978 to 2009. Relationships between mean winter air temperatures, cumulative freezing degree days (CFDD) and the sum of daily ice area are found for the first time. Mean monthly air temperatures of less than 5.5-9.5°C, and a minimum CFDD of 3.6-11.2°C, is required for ice formation in the Northern Caspian. Examination of climate projections from multi-model ensembles of monthly mean air temperatures suggest for the first time that the Northern Caspian may be largely ice-free by 2100 for the highest emission scenario. An ocean-ice-atmosphere model of the Caspian shows weak sensitivities of the minimum CFDD to varied sea-ice albedo and ice compressive strength. Sea level decline reduces the minimum CFDD and promotes formation of higher concentration ice. An atmosphere model of the Caspian is run with observed 2006 to 2009 sea-ice cover, with an additional run without ice cover, to quantify the sensitivity of the atmosphere to sea-ice for the first time. Ice cover removal results in up to 5-10% increase in precipitation, surface wind speeds and humidity, with up to 3°C increase in surface temperature, in the December-January-February climatology over the Northern Caspian. Additionally, extreme precipitation and extreme wind speeds intensify and extreme cold air events weaken with ice removal.
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Carson, Nuala. "Numerical modelling of landfast sea ice." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/18773/.
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Landfast sea ice is a recurring seasonal feature along many coastlines in the polar regions. It is characterised by a lack of horizontal motion, for at least 20 days, and its attachment to the coast or seabed. It can form as a result of restrictive geometry, such as channels or embayments, or through the grounding of thick ice ridges which add lateral stability to the ice cover. Due to its stationary and persistent nature, landfast ice fundamentally modifies the exchange of heat and momentum between the atmosphere and ocean, compared with more mobile pack ice. The current generation of sea ice models is not capable of reproducing certain aspects of landfast ice formation and breakup. In this work two landfast ice parameterisations were developed, which describe the formation and breakup of landfast ice through the grounding of thick ice ridges. The parameterisations assume the sub-grid scale distribution of ice draft and ocean depth, the two parameters important in determining the occurrence of grounded ridges. The sub-grid scale distribution of grounded ice is firstly defined by assuming that ice draft and ocean depth are independent. This parameterisation allowed ice of any thickness to occur and ground at any depth. Advancing from this the sub-grid scale distribution of the grounded ice was restricted in an effort to make it more realistic. Based on Arctic ice scour observations ice was prevented from grounding in regions where the draft thickness was much larger than the ocean depth. Both parameterisations were incorporated into a commonly used sea ice model, the Los Alamos Sea Ice Model (CICE), to which a multi-category ocean depth distribution from high resolution global bathymetry data (ETOPO1) was included. The parameterisations were tested in global standalone format (i.e. no active ocean) with realistic atmospheric forcing. Both parameterisations were found to improve the spatial distribution and the seasonal cycle of landfast ice compared to the control (i.e. no landfast ice parameterisation) in the Arctic and Antarctic. However, the grounded ridges produced by the parameterisations were very stable, and tended to become multiyear leading to the production of multiyear landfast ice, which was particularly widespread in the Antarctic. It was found that tides have a significant impact on both grounded and landfast ice. In some polar locations tides were found to increase the occurrence of landfast ice, by increasing the production of thick ridges which were able to ground. Conversely, in some regions, tides were found to decrease the occurrence of landfast ice, as strong tidal and residual currents increased the mobility of the grounded ridges and landfast ice. This thesis finishes by considering whether a sea ice model could be used to further our understanding of the physical landfast ice system. Analytically derived characteristic numbers, which describe the ability of landfast ice to form, were found to fully describe the formation of landfast ice within the sea ice model CICE during idealised 1D scenarios. For these scenarios the key parameters controlling ice motion were found to be the external forcing component, the width of the ice cover, the internal ice strength, and the thickness of the ice. However, an exact characteristic variable able to describe the occurrence of landfast ice in an idealised 2D scenario could not be found analytically, nor could it be inferred numerically, and this remains an area for further research. This thesis examines different methods of modelling landfast sea ice and provides the sea ice modelling community with a means to parametrise landfast ice formation as a result of grounded ridges without having to work at very fine resolution, as this is computationally inefficient.
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Butler, Benjamin Miles. "Mineral dynamics in sea ice brines." Thesis, Bangor University, 2016. https://research.bangor.ac.uk/portal/en/theses/mineral-dynamics-in-sea-ice-brines(a3538f3c-3d4a-4b28-beb4-27dd8c65136e).html.
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The sea ice microstructure is permeated by millimetre to micrometre sized inclusions filled with concentrated seawater-derived brine. It is within these brines that the in-situ chemical and biological reactions occur. The brines are confined to a temperature-dependent composition, becoming more concentrated and reducing in volume with decreasing temperature. Upon sufficient cooling the coupled effects of lower temperature and higher salinity results in the brine exceeding the solubility of a mineral, which precipitates. Given the complex composition of seawater, there are several minerals that can exceed saturation within the polar temperature spectrum, each with their own dynamics and environmental significance. This thesis investigates mirabilite (Na2SO4 10H2O), gypsum (CaSO4 2H2O) and hydrohalite (NaCl 2H2O). The small crystal size ( m), temperature dependence, and solubility of these minerals acts to limit the scope for studying their existence and behaviour in sea ice with field experiments. For these reasons, their dynamics have been investigated in a laboratory setting using synchrotron X-ray powder distraction experiments, and measurements of mineral solubility in solutions representative of sea ice brines at thermal equilibrium. The experimental observations are supplemented with model predictions, and together are used to provide a comprehensive assessment of the existence, role and e ects of mineral precipitation in sea ice. Mirabilite and hydrohalite are found to cause substantial changes to brine composition and the sea ice microstructure, and are observed to interact in accordance with equilibrium crystallisation. The precipitation of mirabilite is also found to have implications for the measurement of sea ice brine salinity. In contrast, the solubility of gypsum displays complex dynamics between 0.2 and -25 °C, and is shown to be highly dependent upon the SO²⁻₄ concentration, resulting in the processes of mirabilite precipitation and dissolution controlling the fate of gypsum in sea ice.
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Anderson, Hyrum Spencer. "Polar Sea Ice Mapping for SeaWinds." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/36.
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In recent years, the scientific community has expressed interest in the ability to observe global climate indicators such as polar sea ice. Advances in microwave remote sensing technology have allowed a large-scale and detailed study of sea ice characteristics. This thesis provides the analysis and development of sea ice mapping algorithms for the SeaWinds scatterometer. First, an in-depth analysis of the Remund Long (RL) algorithm for SeaWinds is performed. From this study, several improvements are made to the RL algorithm which enhance its performance. In addition, a new method for automated polar sea ice mapping is developed for the SeaWinds instrument. This method is rooted in Bayes decision theory, and incorporates an adaptive model for seasonally fluctuating sea ice and ocean microwave signatures. The new approach is compared to the RL algorithm, to passive microwave data, and to high-resolution SAR imagery for validation.
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Himmich, Kenza. "Antarctic sea ice : a seasonal perspective." Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS105.
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La banquise antarctique a subi une réduction brutale en 2016, après plus de quatre décennies d'une lente augmentation. Une telle évolution pourrait avoir de larges conséquences, compte tenu de l'importance de la banquise antarctique pour le climat, l'océan et l'écosystème marin polaire local. Pourtant, les modèles climatiques ne parviennent pas à reproduire les changements observés, laissant planer une incertitude considérable quant à leur origine et à leurs conséquences. Cette déficience des modèles est en partie due à une mauvaise compréhension des processus fondamentaux liés à la banquise antarctique. Dans cette thèse, nous contribuons à faire progresser cette compréhension, en adoptant une perspective saisonnière. Les processus moteurs de l'avancée et du retrait saisonniers de la banquise sont explorés. En particulier, les rôles possibles d'un préconditionnement thermodynamique, des flux de chaleur air-glace-mer et de la dynamique de la banquise sont étudiés. Nous montrons, dans l'état moyen, que les dates d'avancée et de retrait de la banquise sont largement contrôlées par des processus thermodynamiques, à travers un préconditionnement respectif du contenu thermique de la couche de mélange et de l'épaisseur de la banquise. Les variations des flux de chaleur air-glace-mer et la dynamique de la banquise ont une importance significative mais secondaire. Ces conclusions sont étayées par un modèle thermodynamique simple, des analyses d'observations et un modèle glace-océan (NEMO). Nous montrons également que les changements récents dans la saisonnalité de la banquise sont principalement dus à des processus thermodynamiques, comme pour l'état moyen. La réduction de la banquise antarctique suivant l'année 2016 coïncide avec un recul plus précoce et une avancée plus tardive de la banquise, à l'échelle quasi-circompolaire. Notre analyse relie ces changements à une glace plus fine en hiver, une fonte plus rapide au printemps et un océan de surface plus chaud en été, en accord avec les processus de la rétroaction glace-albédo. L'empreinte circumpolaire de ces changements leur suggère une cause océaniqueAntarctic sea ice has undergone an abrupt reduction in 2016, following more than four decades of a slow increase. This could have wide-ranging consequences given the importance of Antarctic sea ice for climate, ocean, and local ecosystem. Yet, climate models fail to capture this observed evolution, leaving considerable uncertainty regarding its origin, impacts and future evolution. Models failure relates, but not only, to a poor understanding of fundamental Antarctic sea ice processes. In this thesis, we contribute to progress understanding of Antarctic sea ice, adopting a seasonal perspective. We investigate the drivers of seasonal sea ice edge advance and retreat, analyzing the roles of thermodynamic preconditioning, air-ice-sea heat fluxes and sea ice dynamics. We show that, in the mean state, timings of ice edge advance and retreat are largely controlled by thermodynamics, via preconditioning from mixed layer heat content and sea ice thickness, respectively. Variations in air-ice-sea heat fluxes and sea ice dynamics have a significant but secondary importance. This conclusion is supported by a simple thermodynamic model, observational analyses and the NEMO ice-ocean model. We also show that recent changes in sea ice seasonality are mainly driven by thermodynamics, similar to the mean state. The reduction in Antarctic sea ice following 2016 coincides with nearly circumpolar earlier retreat and later advance of the ice edge. Our analysis links these changes to thinner ice in winter, faster melt in spring and warmer upper ocean in summer, in line with ice-albedo feedback processes. Based on the circumpolar footprint of these changes, we argue that they likely have an oceanic origin
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Huddleston, M. R. "Modelling the sea ice thickness distribution in the Greenland Sea." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604716.
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Following a detailed review of the history and theory of sea ice modelling in the Arctic, a further review is made of previous analysis of the ice thickness distribution. In addition to this, ten new or partially cited upward looking sonar ice draft datasets derived from moored buoys and submarine profiles have been used to provide a detailed set of statistics for comparison with modelled ice thickness distribution functions in the Greenland Sea. The moored sonar buoys datasets are from the period 1991-1994 and the submarine datasets are from the spring seasons of 1987 and 1991. Suitable atmospheric and oceanic forcing fields for 1991-94 have been derived from UK Meteorological Office unified model simulations and analysis and verified for a sea ice model of the Arctic Ocean and Greenland Seas. The model represents the sea ice thickness distribution using 28 levels of ice after Flato and Hibler [1995]. The use of synoptic daily varying winds is shown to create coastal polynyas and the application of spatially and temporally varying precipitation fall generated a realistic snow cover. An extensive comparison of modelled and observed ice thickness distributions is presented for the Greenland Sea. Ice fluxes for Fram Strait have been produced using a variety of methods using data from moored upward looking sonar thickness distributions, SSM/I ice concentrations and International Arctic Buoy Programme derived drift data. Results show that it is important to include the variation in the thickness and velocity fields both spatially and temporally across Fram Strait in the calculation of ice fluxes. The modelled variation in the velocities, thickness distributions and the ice fluxes in Fram Strait compare well with the observations although the absolute value of the fluxes are too low due to excessive winter oceanic heat fluxes. When the observed fluxes were used in a boundary-forced Greenland Sea regional model, it was shown that the mechanisms that preferentially melt ridged ice types not present in the model but the decay of the mean thickness of the ice downstream can be represented. Overall, the model results emphasise the need for further work on dynamic-thermodynamic coupling in ice models to resolve these processes.
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Mathew, Nizy. "Retrieval of surface emissivity of sea ice and temperature profiles over sea ice from passive microwave radiometers." Berlin Logos, 2007. http://d-nb.info/997387483/34.
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Roth, Mathias K. "Effects of thermobaricity on coupled ice-mixed layer thermodynamics." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FRoth.pdf.
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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2003.Thesis advisor(s): Roland W. Garwood, Arlene Guest. Includes bibliographical references (p. 59-61). Also available online.
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Görgen, Klaus. "Sensitivitätsstudien und Analyse von Atmosphäre-Meereis-Wechselwirkungen mit dem regionalen Atmosphärenmodell HIRHAM4 auf Basis eines neu entwickelten beobachtungsgestützten unteren Modellantriebs während ausgewählter Sommer über der Arktis, Laptewsee = Sensitivity studies and analysis of atmosphere-sea-ice-interactions with the regional atmospheric model HIRHAM4 using a newly developed observational lower boundary forcing dataset during selected summers over the Arctic/Laptev Sea /." Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung, 2006. http://www.gbv.de/dms/bs/toc/517265761.pdf.
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Yu, Yanling. "Regional Arctic ice thickness and brine flux from AVHRR /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/11067.
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Swick, William A. "High latitude coupled sea-ice-air thermodynamics." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Sep%5FSwick.pdf.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, Sept. 2004.Thesis advisor(s): Roland W. Garwood. Includes bibliographical references (p. 71-73). Also available online.
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Gorman, Robert William Carleton University Dissertation Geography. "Sea ice characteristics of the Parry Channel." Ottawa, 1988.
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Palais, Julie Michelle. "Tephra layers and ice chemistry in the Byrd-Station ice core, Antarctica." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299252349.
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Tadross, Mark Alexander. "Microwave remote sensing of young sea ice in the Greenland Sea." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624765.
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Reddy, Tasha Elise. "Oceanography of the Ross Sea : ocean circulation, sea ice, and phytoplankton /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Mårtensson, Sebastian. "Ridged sea ice modelling in climate applications." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-93977.
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This work aims to increase our understanding of the nature of large scale features of sea ice from a dynamics point of view.Sea ice plays an important part in the exchange of heat and humidity between sea and air and thus is an important component of the climate system. Its physical presence also directly impacts the various forms of life such as diatoms, polar bears and humans alike.The dynamics of sea ice affect both weather and climate, through the large scale drift in the Arctic from the Siberian coast towards Fram Strait, through creation of cracks in the ice called leads or polynyas, and through ridging and other mechanical deformations of ice floes.In this work, we have focused on modelling of ridged ice for a number of reasons. Direct observations of the internal ice state is very difficult to perform and in general, observations of sea ice are either sparse or of limited information density. Ridged ice can be seen as the memory of high ice stress events, giving us a view on these highly dynamic events. Ridging is of major importance for the ice thickness distribution, as the thickest ice can only be formed through mechanical processes. Further, ridged ice is of direct interest for anyone conducting shipping through seasonal or perennial ice covered seas as it can form impenetrable barriers or in extreme even cases crush a ship caught within the ice pack. To this end, a multi-category sea ice model, the HELsinki Multi category Ice model (HELMI), was implemented into the Rossby Centre Ocean model (RCO). HELMI has explicit formulations for ridged and rafted ice, as well as sub-grid scale ice thickness distribution (a feature shared with other multi category models) and an ice strength based on energetics. These features give RCO better representation of sub-grid scale physics and gives us the possibility to study the deformed ice in detail. In paper I we look at the change in behaviour in the Arctic as the ice becomes more mobile, leading to a slight increase in modelled ridged ice volume in the central Arctic, despite a general trend of a decreasing ice cover.Paper II takes us to the Baltic Sea and the possibilities of modelling ridge ice concentration with a statistical model.In Paper III we investigate how the diminishing ice cover in future scenarios affects the biological activity in the Baltic Sea.Finally Paper IV investigates how the ice stress and the internal ice force can be interpreted in terms of ice compression on the ship scale.At the time of the doctoral defence the following paper was unpublished and had a status as follows: Paper 4: Manuscript
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Cruz, García Rubén. "Seasonal Arctic sea ice predictability and prediction." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670223.
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Arctic sea ice plays a central role in the Earth’s climate. Changes in the sea ice on seasonal-to-interannual timescales impact ecosystems, populations and a growing number of stakeholders. A prerequisite for achieving better sea ice predictions is a better understanding of the underlying mechanisms of sea ice predictability.
In the first part, we investigate the seasonal-to-interannual Arctic sea ice predictability in perfect-model experiments performed with six different climate models. Similar pan-Arctic winter sea ice extent (SIE) reemergence is found for HadGEM1.2, GFDL-CM3 and E6F, while a sea ice volume (SIV) persistence from 1 to 3 years is confirmed for all models. Similarities in winter SIE predictability remergence in the GIN seas and Baffin Bay are found even though models have distinct sea ice states. A summer SIV skill reemergence is also found in the Barents, Kara and Chukchi seas. A regional analysis in EC-Earth2.3 suggests that Arctic basins can be classified according to three distinct regimes. The central Arctic drives most of the pan-Arctic SIV persistence. In peripheral seas, predictability for the SIE in winter is associated with ocean thermal anomalies persistence. The Labrador Sea exhibits the longest predictability (up to 1.5 years), the reemergence of predictability in winter being driven by the advection of heat content anomalies along the subpolar gyre.
In real predictions, forecast errors appear due to inconsistencies between the initial states of the different model components and to the development of the inherent model biases. We identify and quantify the contribution of initial condition (IC) inconsistencies and systematic model errors to the forecast model errors in two sets of seasonal forecasts (May and November initialized) produced with EC-Earth3.2 during the first forecast month. After 24 (19) days, the inherent model biases become the largest contributor to the forecast error for the May (November) initialized forecasts, while the initial inconsistency dominates in the previous days. This initial inconsistency is mostly associated to a mismatch between the sea ice and ocean ICs, with a marginal role associated to differences with the atmosphere. The development of both types of errors is sensitive to the month of initialization: the initial shock is more pronounced in November than in May because the initial ocean is warmer and less consistent with the initial sea ice cover, in both cases the shock leading to sea ice melting.
The last part compares three seasonal forecast systems based on EC-Earth and initialized through three different strategies: (1) using both the sea ice and ocean ICs from a native reconstruction that assimilates ORAS4 temperature and salinity with a weak surface restoring coefficient, (2) taking the sea ice ICs from the same reconstruction as in 1 and the oceanic ICs from ORAS4 and (3) the same as in 1 but using a stronger restoring coefficient. The objective is to assess the impact of these methods on the sea ice bias and skill. Strategy 2 induces an initial shock because of a too warm polar surface ocean in ORAS4 for the reconstructed sea ice ICs. For strategy 3, a strong ocean nudging towards ORAS4 produces a too warm ocean and a sea ice deficit. For the prediction initialized using method 1, no shocks are observed. The sea ice errors of strategies 2 and 3 converge in less than a month, demonstrating the role of the ocean ICs in driving the sea ice biases. Although no significant differences appear between the sea ice prediction skill of the three forecast systems, all three show significantly higher skill than the historical experiment for the pan-Arctic SIE during the first two months. The Labrador Sea is the only basin with a significant added value of initialization during the 7 months of prediction, whereas only about 3 months of added-value are detected in the peripheral basins.El hielo marino del Ártico juega un papel central en el clima de la Tierra. Los cambios en el hielo marino en escalas temporales estacionales a interanuales afectan a los ecosistemas, las poblaciones y un número creciente de sectores socio-económicos. Para lograr mejores predicciones de hielo marino se necesita una mejor comprensión de los mecanismos subyacentes de su predictibilidad. En la primera parte, investigamos la predictibilidad del hielo marino del Ártico en escalas de tiempo estacional a interanual en experimentos de modelo perfecto realizados con seis modelos climáticos diferentes. Se observa una reemergencia similar de la extensión del hielo marino (SIE) de invierno panártico para HadGEM1.2, GFDL-CM3 y E6F, mientras que se confirma una persistencia del volumen de hielo marino (SIV) de 1 a 3 años para todos los modelos. Se encuentran similitudes en la reemergencia de predictibilidad de invierno del SIE en los mares GIN y la Bahía de Baffin a pesar de que los modelos tienen estados de hielo marino distintos. Un análisis regional en EC-Earth2.3 sugiere que las cuencas árticas se pueden clasificar de acuerdo con tres regímenes distintos. El Ártico central contribuye en mayor parte a la persistencia del SIV panártico. En los mares periféricos, la predictibilidad del SIE en invierno está asociada a la persistencia de anomalías térmicas oceánicas. El Mar de Labrador exhibe la predictibilidad más larga (hasta 1.5 años), y el resurgimiento de la predictibilidad en invierno se debe a la advección de anomalías en el contenido de calor del océano en el giro subpolar del Atlántico Norte. En las predicciones reales, los errores de predicción aparecen debido a inconsistencias entre los estados iniciales de las diferentes componentes del modelo y al desarrollo de errores inherentes al modelo. Cuantificamos la contribución de las inconsistencias de las condiciones iniciales (ICs) y los errores sistemáticos del modelo a los errores de predicción en dos sistemas de predicciones estacionales (inicializados en mayo y noviembre) producidos con EC-Earth3.2. Después de 24 (19) días, los errores inherentes del modelo se convierten en el mayor contribuyente al error de predicción para las predicciones inicializadas en mayo (noviembre), mientras que la inconsistencia inicial domina durante los días anteriores. Esta inconsistencia inicial se asocia principalmente a un desajuste entre las ICs del hielo marino y del océano, con un papel marginal asociado a las diferencias con la atmósfera, que lleva al derretimiento del hielo marino. La última parte compara tres sistemas de predicción estacional basados en EC-Earth e inicializados a través de tres estrategias diferentes: (1) utilizando las ICs del hielo marino y del océano de una reconstrucción nativa que asimila la temperatura y la salinidad de ORAS4 con un coeficiente de restauración superficial débil (2) tomando las ICs de hielo marino de la misma reconstrucción que en 1 y las ICs oceánicas de ORAS4 y (3) igual que en 1 pero usando un coeficiente de restauración más fuerte. El objetivo es evaluar el impacto de estos métodos en el error y la habilidad predictiva del hielo marino. La estrategia 2 induce un choque inicial debido a un océano de superficie demasiado cálido en ORAS4 para las ICs del hielo marino. Para la estrategia 3, una asimilación fuerte del océano hacia ORAS4 produce un océano demasiado cálido y un déficit de hielo marino. Para la predicción inicializada utilizando el método 1, no se observan choques. Los errores del hielo marino de las estrategias 2 y 3 convergen en menos de un mes, lo que demuestra el papel de las ICs oceánicas en la conducción de los errores de hielo marino. Los tres sistemas de predicción muestran una habilidad significativamente mayor que el experimento histórico (pero no entre ellos) para el SIE panártico durante los primeros dos meses. El mar de Labrador es la única cuenca con un valor añadido significativo por la inicialización durante toda la predicción (7 meses), mientras que solo se detectan aproximadamente 3 meses de valor añadido en las cuencas periféricas.
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Stone, Megan M. "Long-range forecasting of Arctic sea ice." Thesis, Monterey, California : Naval Postgraduate School, 2010. http://edocs.nps.edu/npspubs/scholarly/theses/2010/Jun/10Jun%5FsTONE.pdf.
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Thesis (M.S. in Meteorology)--Naval Postgraduate School, June 2010.Thesis Advisor(s): Murphree, Tom ; Meyer, David. "June 2010." Description based on title screen as viewed on July 14, 2010. Author(s) subject terms: Arctic, Sea Ice, Sea Ice Concentration, Beaufort Sea, Military Operations, Climate, Climatology, Climate Analysis, Climate Prediction, Long-range Forecast, Statistical Forecast, Meteorology, Arctic Oscillation, North Atlantic Oscillation, Caribbean Sea. Includes bibliographical references (p. 89-92). Also available in print.
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O'Farrell, Siobhan Patricia. "Ocean fronts formed at sea ice boundaries." Thesis, University of Cambridge, 1989. https://www.repository.cam.ac.uk/handle/1810/268046.
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Meltwater input from sea ice forms a buoyancy source for the upper ocean which creates a strong density gradient in both horizontal and vertical directions. If, in particular, the ocean density front is formed in the Bering sea during winter, the frontal dynamics are influenced by local shelf/slope processes. further, ice is advected across the front by the wind, thereby altering the heat flux to the ice and leading to an increase in the freshwater buoyancy flux to the ocean. Hence, th~ surface manifestation of the front is governed by ice position. In this thesis a detailed study of ice and ocean parameters in such a system is presented using data from the 1982-3 winter Season in the Bering sea. Particular attention is given to the results from MIZEX-West (1983), an intensive mid-winter study. Modelling of the physical processes involved in the development of the meltwater front follows two directions; firstly the buoyancy input to small scale fronts formed in the summer marginal ice zone is considered and secondly, an hierarchy of numerical models of ice and ocean dynamics are employed. Results are also reported of fieldwork carried out in the East Greenland current (MIZEX-84, LANCE cruise) using a novel, medium resolution, portable CTD system to measure upper ocean density gradients from floe edges and small boats. However, during these experiments conditions were not ideal for the development of meltwater fronts analogous to those found in the Bering Sea. Additionally, one-dimensional and two-layer quasi-steady ocean models coupled to an ice cover are discussed. These models proved useful tools in our understanding of the air-ice-ocean exchanges and frontal adjustment processes within the more complex system. More detailed modelling studies were undertaken using a two-dimensional, coupled ice-ocean model focusing on the interactive thermodynamic forcing during ice ablation and ice accretion. The thermal and salinity fluxes in the coupling were related to the ice growth calculated by a thermodynamic ice model similar to those is employed by larger scale climate studies. Hence, over short time scales the ice growth in leads and open water that may occur after a change in external forcing conditions is not well represented. The functional form of the internal stress in the ice momentum equation is investigated with the model. When the amplitude of the internal stress decreases by several orders of magnitude in a few grid points the model was unable to sustain such a gradient and was liable to generate numerical instabilities. If however, the near discontinuity in the internal stress at the ice edge is treated like a moving shock wave (after Roed and O'Brien, 1983) then the ice compactness maintains a coherent ice edge under conditions simulating the passage of a storm.
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Crocker, Gregory Bruce. "Physical processes in Antarctic landfast sea ice." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278282.
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Garcia, Frank W. Jr. "Sea ice classification using synthetic aperture radar." Thesis, Monterey, California: Naval Postgraduate School, 1990. http://hdl.handle.net/10945/27745.
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Approved for public release; distribution is unlimited.This study employs Synthetic Aperture Radar (SAR) imagery from the Marginal Ice Zone Experiment (MIZEX) 1987 to identify an optimal set of statistical descriptors that accurately classify three types of ice (first-year, multiyear, odden) and open water. Two groups of statistics, univariate and texture, are compared and contrasted with respect to their skill in classifying the ice types and open water. Individual statistical descriptors are subjected to principal component analysis and discriminant analysis. Principal component analysis was of little use in understanding features of each ice and open water group. Discriminant analysis was valuable in identifying which statistics held the most power. When combined, univariate and texture statistics classified the groups with 89.5% accuracy, univariate alone with 86.8% accuracy and texture alone with 75.4% accuracy. Range and inertia were the strongest univariate and texture discriminators with 74.6% and 50.8% accuracy, respectively. Despite the use of a non-calibrated SAR, univariate statistics were able to classify the images with greater accuracy than texture statistics.
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Feltham, Daniel Lee. "Fluid dynamics and thermodynamics of sea ice." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275389.
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Garcia, Frank W. "Sea ice classification using synthetic aperture radar." Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA232248.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 1990.Thesis Advisor(s): Nystuen, J.A. ; Bourke, R.H. "June 1990." "MPS-68-90-004." Description based on title screen as viewed on March 24, 2010. DTIC Identifier(s): Radar Images, Sea Ice, Marginal Ice Zones, Ice Classification, Statistical Analysis, Gray Scale, Odden Ice, Theses. Author(s) subject terms: Synthetic Aperture Radar, Sea Ice Classification, Marginal Zone, Gray Level Co-Occurrence Matrices, Texture Statistics, Univariate Statistics, MIZEX '87 SAR Data. Includes bibliographical references (p. 96-98). Also available in print.
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Heorton, H. D. B. "Jet formation at the sea ice edge." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1391815/.
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Mesoscale jet formation due to the Coriolis Effect is well understood over sharp changes in surface roughness such as coastlines. This sharp change in surface roughness is experienced by the atmosphere flowing over, and ocean flowing under, a compacted sea ice edge. Sea ice edge jets have been observed. This thesis presents a study of a dynamic sea ice edge responding to atmospheric and oceanic jet formation during various wind and ocean current conditions. An idealised analytical model of sea ice drift is created using a momentum balance and the viscous plastic rheology. This is compared to an ice edge in the Los Alamos sea ice climate model (CICE) run on an idealised domain. A scheme has been developed which analyses sea ice concentration and adds jets to the CICE model forcing data. The response of the model to jet formation is tested at various resolutions. The formation of atmospheric jets at the sea ice edge is shown to increase the wind speed parallel to the sea ice edge and results in the formation of a sea ice edge jet. The increase is dependent upon the angle between the ice and wind and results in an increase in ice transport along the sea ice edge of 40%. Observa- tions and climate model data of the polar oceans has been analysed to show areas of likely atmospheric jet formation with the Fram Strait being of particular interest. The possibility of oceanic jet formation and the resultant effect upon the sea ice edge is less conclusive. The coupling between the components of climate models is currently crude and does not allow for jet formation. Most climate model also misrepresent the ice drift through the Fram Strait leading to errors in the prediction of Arctic sea ice extent.
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Johnston, Michelle E. "Influence of ice microstructure on the microwave scattering properties of sea ice." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0013/NQ36280.pdf.
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Schannwell, Clemens. "Modelling ice dynamic sea-level rise from the Antarctic Peninsula Ice Sheet." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7775/.
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The Antarctic Peninsula (AP) has been one of the most rapidly warming regions on this planet. This warming has been accompanied by major glaciological changes such as tidewater glacier retreat, ice-shelf retreat and collapse alongside acceleration of outlet glaciers in response to ice-shelf removal. As faster owing glaciers deliver more ice from the ice sheet's interior to the margins, the AP has been identified as an important contributor to global sea-level rise (SLR). However, comprehensible SLR projections of the AP induced by ice dynamics over the next three centuries are still lacking. In this thesis, numerical ice-sheet models are utilised to present scenario-based ice dynamic SLR projections for the AP.
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Guo, Wenkai. "The relationship between sea ice retreat and Greenland ice sheet surface-melt." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397692613.
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Scoto, Federico <1991>. "Halogens in ice core as potential proxies for past sea ice reconstructions." Doctoral thesis, Università Ca' Foscari Venezia, 2019. http://hdl.handle.net/10579/17845.
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Da circa cinquanta anni, il ghiaccio marino in Artico sta diminuendo, sia in estensione che in volume, ad un tasso di gran lunga più veloce rispetto a quanto previsto dai modelli numerici. Sebbene a partire dai primi anni ’70 (ovvero la cosiddetta “era satellitare”), siano state acquisite numerosissime informazioni sul suo stato, vi è ancora una mancanza di conoscenza circa la sua evoluzione prima dell’avvento delle misurazioni strumentali.
Per colmare questa lacuna, vengono comunemente utilizzati paleo-registri come sedimenti marini e carote di ghiaccio. In particolare, alcuni studi hanno identificato il bromo contenuto all’interno di carote di ghiaccio come un potenziale indicatore di condizioni di ghiaccio di neoformazione (o di 1° anno).
Durante la primavera polare, infatti, a causa di reazioni fotolitiche che avvengono in prossimità della superficie del ghiaccio marino stagionale, vi è un efficiente riciclo di bromo inorganico che ne determina un aumento delle sue concentrazioni in fase gassosa rispetto a quella misurata al di sopra della superficie dell'oceano, del ghiaccio marino pluriennale o del suolo artico. Questo processo, noto come "esplosione del bromo", viene rilevato anche dai satelliti oltre che da misure in loco, iniziando i primi di marzo protraendosi fino a fine maggio.
Dopo l'emissione, il plume arricchito in bromo viene preso in carico dalle circolazioni cicloniche presenti nella bassa troposfera polare fino a quando, raggiunta la terraferma, precipita sotto forma di neve che sarà, anch’essa, arricchita in bromo rispetto al rapporto Br/Na dell'acqua di mare.
Utilizzando l’arricchimento di bromo proveniente da diverse carote di ghiaccio artiche, questa tesi è stata ideata seguendo una duplice prospettiva. Da un lato, mira a validare e calibrare il tracciante proposto con immagini satellitari del ghiaccio marino artico per il periodo 1984-2016. Dall’altro, una volta validato il tracciante, si vuole applicare l’informazione rinvenuta ad un caso di studio paleoclimatico che si pone come obiettivo quello di valutare la risposta del ghiaccio marino alle brusche instabilità climatiche dell'ultimo periodo glaciale (gli eventi D-O).
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Parise, Cláudia Klose. "Sensitivity and memory of the current mean climate to increased Antarctic sea ice: The role of sea ice dynamics." Instituto Nacional de Pesquisas Espaciais (INPE), 2014. http://urlib.net/sid.inpe.br/plutao/2014/11.19.18.13.
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Esta tese estuda a sensibilidade e memória do clima global ao aumento do gelo marinho Antártico, levando em consideração o tempo de persistência dos máximos de gelo (concentração e espessura) sob condições climáticas atuais. A sensibilidade das \emph{storm tracks} no Hemisfério Sul e do clima da América do Sul ao aumento do gelo marinho também são analisadas, bem como o mecanismo envolvido na restauração do equilíbrio climático. Dois grupos de experimentos foram realizados. No primeiro o gelo marinho é simulado por um modelo de única camada que desconsidera a reologia do gelo, impedindo que o gelo mova quando espesso. No segundo, o gelo marinho é simulado por um modelo multi-camadas que resolve explicitamente a dinâmica do gelo. Cada clima é perturbado com um extremo de condições positivas (\emph{Max}) e climatológicas (\emph{ctl}) de concentração e espessura de gelo marinho Antártico em um conjunto de 30-membros integrados por 10 anos cada. Alterações nas \emph{storm tracks} são analisadas através de um método automatizado de identificação e rastreio de ciclones extratropicais com base em vorticidade relativa. Os resultados mostram que um extremo de gelo marinho Antártico é capaz de persistir $\sim$4-anos sob condições climáticas atuais. Nos 4 anos seguintes o gelo marinho nos experimentos \emph{Max} é semelhante àquele dos experimentos \emph{ctl} e nos últimos 2-anos as diferenças (\emph{max- ctl}) de gelo marinho são negativas. A persistência dos máximos de gelo marinho varia setorialmente e em função do tipo de modelo de gelo. A presença de máximos de gelo marinho Antártico reduz a temperatura do ar dos baixos aos médios níveis da troposfera. O resfriamento das altas latitudes aumenta o transporte de calor para sul e a convergência em baixos níveis. A pressão média ao nível do mar é reduzida (aumentada) sobre as altas (médias) latitudes, padrão típico da fase positiva do Modo Anular Sul. O fluxo de calor sensível do oceano para a atmosfera é intenso nas margens do gelo marinho, onde a baroclinia da atmosfera também aumenta. Os ventos de oeste se intensificam ao sul de $50^{0}$S e se enfraquecem entre $45^{0}$S e $10^{0}$S. A corrente de jato polar se intensifica em direção aos pólos enquanto o jato subtropical se enfraquece em direção ao equador. Em resposta ao fortalecimento do jato polar, a densidade de trajetóricas dos ciclones, ciclogênese e ciclólise aumenta sobre as altas (médias) latitudes. Com o deslocamento das tempestades para sul, a atividade dos distúrbios transientes é reduzida sobre a América do Sul, bem como a formação de ciclones sobre as duas principais regiões ciclogenéticas (em $30^{0}$S e $45^{0}$S). O enfraquecimento do jato subtropical contribui para aumentar a estabilidade estática da atmosfera e reduzir a taxa de precipitação sobre a América do Sul. Os fortes ventos de oeste fortalecem a Corrente Circumpolar Antártica e, conseqüentemente, a deriva de Ekman para o norte. O derretimento do máximo de gelo marinho gera uma entrada da água fria e pouco salina na camada de mistura do Oceano Austral. A medida que essa água superficial flui para o norte há ressurgência da água mais quente e salina (observada abaixo da camada de mistura do oceano) na Divergência Antártica ($60^{0}$S). A memória climática ($\sim$8-anos) armazenada nas camadas superiores do oceano modula a intensidade e duração da resposta atmosférica ao máximo de gelo marinho.This thesis explores the sensitivity and memory of the global climate to increased Antarctic sea ice, taking into account the persistence of sea ice maxima (in concentration and thickness) under current climate conditions. Moreover, the sensitivity of the Southern Hemisphere storm tracks and the South America climate to increasedAntartictic sea ice are also studied as well as the mechanisms involved in restoring the climate balance. In order to isolate the impacts of sea ice dynamics, two sets of sensitivity experiments are performed with the GFDL CM2.1 coupled climate model. In the first set the sea ice is simulated by a simple slab sea ice model which neglects the sea ice dynamics whereas in the second the sea ice is simulated by a sophisticated multi-layer model. The current climate is perturbed with maximum conditions of Antarctic sea ice (max) and compared to the respective control simulation (ctl). The four numerical experiments are integrated for 10 years each in a large 30-member ensemble. The changes to the Southern Hemisphere extratropical cyclones are analysed through an automated of cyclone identification and tracking based on relative vorticity. The impact of increased Antarctic sea ice on the South America climate is analysed through changes in the precipitation regime and the associated atmospheric systems. The results show that a maximum condition of Antarctic sea ice is able to persist $\sim$4-years under current climate conditions.In the following 4-years of model integration the sea ice in the max experiments is similar to that of the ctl experiments and in the last 2-years the (max-ctl) sea ice differences are negative. However, the persistence of Antarctic sea ice maxima varies sectorally and according to the sea ice model type. The Antarctic sea ice maxima reduce the air temperature from the low to mid-levels. This increases the poleward meridional temperature gradient, resulting in air ascending over the high-latitudes.The mean sea level pressure is reduced (increased) over the high (mid)-latitudes, a typical pattern of the Southern Annular Mode positive phase. The sensible heat flux from the ocean to the atmosphere is intensified at the sea ice edges increasing the atmospheric baroclinicity there. The westerly winds are intensified south of 50$^{°}$S and weakened from 45$^{°}$S to 10$^{°}$S. The polar jet stream intensifies poleward whereas the subtropical jet stream weakens toward the Equator. In response to the polar jet strengthening, the cyclone track density, cyclogenesis and cyclolysis have increased (decreased) over the high (mid)-latitudes. The eddy activity is reduced over South America as well as the cyclogenesis over the two main regions (at 30$^{°}$S and 45$^{°}$S ). The weaker subtropical jet contributes to enhanced atmospheric static stability and reduces the precipitation rate over South America. The stronger westerlies strengthen the Antarctic Circumpolar Current and, consequently, the Ekman drift northward. The melting of the sea maximum generates an imput of cold and fresh melt water into the ocean mixed-layer of the Southern Ocean (from the surface to 100 m ). As this surface water flows northward there is upwelling of the warmer and saltier water (observes below the ocean mixed-layer) on the Antarctic Divergence (60$^{°}$S). The climate memory stored in the upper ocean layers ($\sim$8-years) modulates the intensity and timing of the atmospheric response.
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Alonso, Arroyo Alberto. "Contributions to land, sea, and sea ice remote sensing using GNSS-reflectometry." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404062.
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This PhD thesis researches the use of passive remote sensing techniques using signals transmitted from the navigation satellites (GNSS) in order to retrieve different geophysical parameters. The thesis consists of two different parts without taking into account the introduction, the state of the art and the conclusions. The first part analyzes the Interference Pattern Technique (IPT), which was previously used in another PhD thesis, and proposes some key improvements. First, the addition of horizontal polarization to the existing vertical polarization is proposed. Then, the retrieval of soil moisture is studied using the horizontal polarization only and combining both polarizations to correct for the surface roughness effects. It is also demonstrated that the phase difference between the two interference patterns is directly related to soil moisture content. A field campaign was conducted in Australia to test empirically all the theoretical developments and algorithms. Secondly, the possibility of measuring Significant Wave Height (SWH) and Mean Sea Surface Level (MSSL) using the IPT is studied. A three month field campaign over coastal sea is devoted to that study. The SWH retrieval is a new estimation algorithm based on measuring the point where the interference pattern loses coherence. The MSSL retrieval is based on the estimation of the IPT oscillation frequency, testing different spectral estimators to improve the accuracy. Since the IPT is limited in coverage due to its static requirements, the research conducted in this thesis migrated to scatterometric GNSS-R techniques. The main goal that migration was to increase coverage of the different GNSS-R instruments. Therefore, the second part of this thesis analyzes the applicability of a scatterometric technique from different platforms: ground-based (mobile and fixed), airborne, and spaceborne. The ground-based still platforms have allowed to develop a soil moisture retrieval algorithm. The ground-based moving platforms have extended the validity of that algorithm. Airborne platforms have been used to study the reflected electric field statistics when the surface reflecting surface is varying (smooth or rough land, and sea). They have also been used to develop different algorithms to measure the coherent and incoherent scattered components depending on the data structure (real-data or complex data). Coherent reflectivity measured from airborne platforms has been compared to other techniques such microwave radiometry, which is highly used in the soil moisture retrieval from spaceborne sensors, and other sensors using optical, multispectral and thermal frequency bands. These relationships between microwave radiometry and GNSS-R measurements suggests the potential synergy of both techniques. A sea ice detection algorithm is also developed using scatterometric GNSS-R data from the UK TDS-1 mission. This algorithm is based on measuring the degree of coherence of the reflected waveform. Finally, a field campaign was conducted to study the effect of vegetation on the GNSS signals that pass through it in order to take into account and correct the effect of vegetation in the GNSS-R data and in the soil moisture retrieval algorithms.Aquesta tesi doctoral aprofundeix en el coneixement de les tècniques de teledetecció passives utilitzant senyals emesos pels satèl·lits de navegació (GNSS) amb l'objectiu de recuperar diferents paràmetres geofísics del terreny. La tesi conté dues parts ben diferenciades a banda de la introducció, estat de l'art i conclusions. La primera part analitza la tècnica coneguda com a patró d'interferències, utilitzada prèviament en una altra tesi doctoral, i proposa certes millores per la seva aplicabilitat. En primer lloc es decideix afegir polarització horitzontal a la ja existent polarització vertical, i s'estudia la recuperació d'humitat del sòl utilitzant només polarització horitzontal i combinant les dues polaritzacions per corregir els efectes de la rugositat del terreny. A continuació es demostra que la mesura de desfasament entre els dos patrons d'interferència està directament relacionada amb la humitat del terreny. Es va realitzar una campanya de mesures a Austràlia per provar empíricament tots els desenvolupaments teòrics i algorismes proposats. En segon lloc s'analitza l'aplicabilitat del patró d'interferències en la mesura de l'altura de les onades (SWH) i del nivell del mar (MSSL), tots dos de forma precisa. L'estimació de l'alçada de les onades és un procés totalment nou basat en mesurar el punt on el patró d'interferències perd la coherència. L'estimació del nivell del mar es basa en l'anàlisi espectral del patró d'interferències provant diferents estimadors espectrals. Atès que la tècnica del patró d'interferència està limitada en cobertura per les seves característiques estàtiques, la investigació duta a terme en aquesta tesi doctoral va migrar cap a tècniques GNSS-R escateromètriques. El principal objectiu a assolir va ser el d'augmentar la cobertura dels diferents instruments GNSS-R de mesura. En conseqüència, la segona part d'aquesta tesi analitza l'aplicabilitat d'aquestes tècniques des de diferents plataformes terrestres (mòbils i fixes), aerotransportades i satèl·lit. Les plataformes terrestres fixes han permès derivar algoritmes de recuperació d'humitat i les mòbils estendre la validació d'aquests. Les plataformes aerotransportades s'han utilitzat per mirar l'estadística del camp elèctric reflectit quan la superfície on es reflecteixen els senyals GNSS va variant (terra plana o terra rugosa, i mar). També han servit per desenvolupar diferents algorismes amb l'objectiu de determinar les components coherent i incoherent del senyal reflectit. De la mateixa manera, dades de reflectivitat coherent mesurades des d'aquestes plataformes han estat comparades amb altres tècniques de teledetecció passiva com la radiometria de microones, altament utilitzada en la mesura d'humitat de terreny, i altres sensors òptics, multi-espectrals, i tèrmics. Aquests resultats han permès suggerir la possible sinergia de dades d'ambdues tecnologies. Un algorisme per detectar la presència de gel sobre el mar també ha estat desenvolupat mitjançant l'ús de dades GNSS-R escateromètriques satel·litals de la missió UK TDS-1. Aquest algorisme es basa en mesurar el grau de coherència de la forma d'ona reflectida. Finalment, s'ha realitzat un estudi de l'efecte de la vegetació en els senyals GNSS que la travessen, per tal de poder corregir aquest efecte en els algoritmes de recuperació d'humitat del terreny.
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Fiedler, Emma. "Air-sea-ice interactions at the Ronne Polynya, southern Weddell Sea, Antartica." Thesis, University of East Anglia, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518354.
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Navarro-Rodríguez, Alba. "Reconstruction of recent and palaeo sea ice conditions in the Barents Sea." Thesis, University of Plymouth, 2014. http://hdl.handle.net/10026.1/3085.
Full textAbstract:
IP25 is a highly branched isoprenoid alkene derived from certain Arctic sea ice diatoms that, when detected in marine sediments, has been used as a proxy for past Arctic sea ice over the last decade. In the current study, the structure of this biomarker was determined following large-scale extraction from sediment material collected from the Canadian Arctic. After purification, the structure of IP25 was confirmed by NMR spectroscopy as being the same as that of a laboratory standard. The purified IP25 was subsequently used to obtain a quantitative (GC-MS) instrumental response factor that could be used to improve the future quantification of IP25 and would help to produce a robust database. IP25, other highly branched isoprenoid (HBI) lipids and some other phytoplanktonic lipids (sterols) were analysed to provide modern and past sediment-based sea ice reconstructions for the Barents Sea. First, a surface sediment study was conducted and biomarker distributions were compared to satellite sea ice records. The occurrence of IP25 was consistent with the presence/absence of seasonal sea ice but there was also evidence of lateral transport of IP25 and other biomarkers in sediments from the southern Barents Sea. In contrast to some previous studies, abundances of IP25, and of those combined with other biomarkers, including sterols, did not show strong quantitative relationships to sea ice concentration. The surface study was used to relate biomarker distributions to recent sea ice and oceanographic conditions and apply this information to long-term sediment records in the eastern and western Barents Sea covering ca. 2 kyr and 11 kyr (Holocene) respectively. IP25 concentrations for the former were found to be very variable and were used to identify the period with maximum sea ice cover occurring from ca. 900 - 400 cal. yr BP where the highest abundances of IP25 and IRD were observed. Similarly, biomarker results from the eastern Barents Sea provided evidence for a dynamic advance of the marginal sea ice zone potentially situated at ca. 78° N (maximum extent) during ca 9.4 – 5.9 cal. kyr BP, to late Holocene and modern day maximum MIZ advance ca. 75° N. Replicate analysis of various biomarkers in individual push-cores collected from a box core obtained from Rijpfjorden (north Svalbard) demonstrated some variability between cores. Variability in individual biomarker concentrations was lowest for HBI lipids and greatest for sterols. These data are consistent with a selective and relatively minor source of the former. In contrast, the somewhat more generic origins of sedimentary sterols likely explain the greater variability in their distributions between cores Finally, the strong abundance relationship between IP25 and a structurally related di-unsaturated HBI (C25:2) was confirmed in all sediments, similar to that found between two tri-unsaturated HBIs, consistent with co-production by certain marine phytoplankton. The progressive use of novel HBIs with two or three degrees of unsaturation (e.g. C25:2 and C25:3) could provide further valuable insights into environmental conditions.
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Heacock, Tony. "Simulation of the seasonal ice regime in Lancaster SoundBarrow Strait." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69661.
Full textAbstract:
A sea ice model developed by W. D. Hibler (1979) was applied to the Lancaster Sound/Barrow Strait channel in an effort to simulate the observed ice environment. The simulation covered a ten month period, from October 1985 until August 1986. The impact of atmospheric and oceanographic forcing on the development of characteristic ice features that develop seasonally within the channel was examined. The importance of the ice interaction component of the model when simulating a restricted channel ice environment was also examined. The model was able to simulate regional scale processes and conditions within the channel. Small scale localised processes and conditions which control the spatial variability and complexity of the ice regime were not accurately reproduced. Simulation results provided insights into the effect and importance of both the model and geophysical variables examined. The study highlighted concerns that need be addressed in future modelling work in the Lancaster Sound/Barrow Strait channel.