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Utilização de bactérias do grupo Lactobacillus casei no desenvolvimento de sorvete potencialmente probiótico de leite de cabra e polpa de cajá (Spondias mombin); Use of bacteria from the Lactobacillus casei group in the development of potentially probiotic goat milk-based ice-cream with yellow mombin (Spondias mombim) pulp

Paula, Clara Mitia de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 13/12/2012 PT
Relevância na Pesquisa
36.99%
O trabalho teve como objetivos desenvolver sorvetes com leite de cabra, polpa de cajá e cepas potencialmente probióticas Lactobacillus rhamnosus HN001 e Lactobacillus paracasei LBC82, verificar a viabilidade dessas cepas e avaliar as características dos produtos ao longo de seu armazenamento a -18ºC por até 12 semanas, bem como a resistência das cepas incorporadas nos produtos a condições gástricas e entéricas simuladas in vitro. Primeiramente, foi desenvolvido creme de leite de cabra para aplicação no produto. Em seguida, foram realizados os ensaios de desenvolvimento dos sorvetes, os quais variaram de acordo com a adição de gordura láctea caprina (sorvetes SC) e a sua substituição por inulina (sorvetes SI) e com a adição de 2 cepas de Lactobacillus - L. rhamnosus HN001 (Lr) e L. paracasei LBC82 (Lp), tendo sido assim denominados: SCr - com gordura láctea caprina + Lr; SCp - com gordura láctea caprina + Lp; SIr - com inulina + Lr; SIp - com inulina + Lp. Os sorvetes foram armazenados a -18±3ºC por até 12 semanas (84 dias) e analisados quanto às seguintes características: overrun (durante a elaboração), fração de derretimento e dureza instrumental (após 14 dias), composição centesimal (após 21 dias)...

Interações entre os ciclones extratropicais e a variabilidade extrema do gelo marinho nos mares de Bellingshausen-Amundsen e no mar de Weddell, Antártica; Interactions between the extratropical cyclones and extreme variability of sea ice in the Amundsen-Bellingshausen Seas and in the Weddell Sea, Antarctic

Carpenedo, Camila Bertoletti
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/05/2012 PT
Relevância na Pesquisa
36.98%
O sistema atmosfera-gelo marinho é complexo e fortemente acoplado. Em uma região de transição entre a cobertura de gelo marinho e o mar aberto a interação entre esse sistema é particularmente intensa, sendo significativa o suficiente para influenciar a circulação atmosférica de grande escala e a distribuição de gelo marinho. Assim, o objetivo principal deste trabalho foi analisar as interações entre os ciclones extratropicais e a variabilidade extrema do gelo marinho nos setores dos mares de Bellingshausen-Amundsen (MBA) e do mar de Weddell (MW), no período de verão e inverno austral entre 1989 e 2007. Foram utilizados dados de extensão de gelo marinho do NSIDC/NASA; campos atmosféricos da superfície até os altos níveis da troposfera das reanálises do ERA-Interim (ECMWF); composição de imagens de satélite do canal infravermelho do SSEC; Índice de Niño Oceânico do CPC/NOAA. As anomalias de alta frequência (período de 2-10 dias) e interanual (período maior que 370 dias) foram obtidas aplicando-se a transformada rápida de Fourier nas séries temporais (1989-2007). Os extremos de gelo marinho foram obtidos através do primeiro e terceiro quartil da distribuição dos dados. As características da circulação atmosférica de alta frequência e interanual associadas aos eventos extremos negativos (ENGM) e positivos (EPGM) de gelo marinho...

Estudo reológico de formulações para sorvetes produzidos com diferentes estabilizantes; Rheological study of ice cream formulations produced with different food stabilizers

Milliatti, Mariana Carniel
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/04/2013 PT
Relevância na Pesquisa
36.99%
Seis formulações para sorvete foram produzidas com diferentes combinações entre os estabilizantes alimentícios Goma Guar, Goma Locusta (LBG) e Gelatina e foram avaliadas durante diferentes etapas de produção: maturação, após batimento e congelamento e após congelamento total. Através dos testes ocilatórios identificou-se que as misturas para sorvetes produzidas com a combinação de Gelatina com Goma Guar e Gelatina com LBG apresentam forte relação entre tempo de maturação e propriedade reológica, o que não foi observado nas formulações contendo cada um dos estabilizantes isoladamente, e nem na formulação contendo a mistura de LBG com Goma Guar. Isso mostra a existência de uma interação forte entre gelatina e galactomananas e que a maturação dessa mistura é essencial para a formação de uma rede contínua e estável. Após maturação de 24 horas, os sorvetes foram produzidos e analisados assim que saíram da produtora a -4°C. As análises conduzidas nesta etapa foram: capacidade de aeração (overrun) e força máxima requerida para extrusão. Quando dois estabilizantes foram combinados percebeu-se menor overrun o que pode ser explicado pelo aumento da viscosidade do sistema quando combinamos dois hidrocolóides...

Desenvolvimento de sorvetes probióticos à base de extrato solúvel de soja; Development of probiotic ice cream from soluble soybean extract

Fernández, Ludmila Carril
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/04/2015 PT
Relevância na Pesquisa
37.01%
Sorvetes são alimentos que apresentam grande potencial como veículo de espécies de micro-organismos probióticos, tendo em vista que apresentam elevada aceitabilidade em todas as faixas etárias. Os alimentos elaborados a base de soja se destacam no mercado devido às inúmeras evidências científicas sobre seus efeitos benéficos à saúde humana. Desta forma, no presente trabalho objetivou-se o desenvolvimento de sorvetes probióticos formulados com diferentes extratos solúveis de soja (in natura e fermentados), utilizando-se a cepa Lactobacillus delbrueckii UFV H2B20. Primeiramente, avaliou-se o desempenho fermentativo (pH e acidez titulável) de 5 cepas de Lactobacillus em meio formulado com os extratos solúveis de soja ESL e ES60, cujos resultados demonstraram que estes extratos são adequados para a formulação de meios de fermentação. Na sequência foram processados sorvetes probióticos formulados com os respectivos extratos in natura (ESL e ES60) e fermentado (ESL F e ES60 F) por Lactobacillus delbrueckii UFV H2B20. Nos sorvetes confeccionados com os extratos na forma in natura, uma suspensão de células da referida cepa foi adicionada à calda previamente ao processo de batimento e congelamento. Os sorvetes foram estocados a -23 ºC por 5 meses e avaliados periodicamente quanto às características físico-químicas (pH...

Evaluation of dehumidification system energy usage in ice rinks

Silva, Diogo Bermejo Pereira Rodrigues da
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2013 ENG
Relevância na Pesquisa
36.96%
Tese de mestrado integrado em Engenharia da Energia e do Ambiente, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2013; Ice skating rinks are one of the largest energy consumers in terms of public buildings due to its simultaneous needs of cooling, heating, ventilation and lighting for different parts of the structure, which means that these facilities have also a lot of potential for saving energy. Saving energy from dehumidification systems in ice rinks is a subject that still needs to be developed and investigated with an increased focus in matters of energy efficiency in these types of structure. The performance of the dehumidification system of diverse ice rinks located near the city of Stockholm, Sweden, is here analysed in order to evaluate the use of energy related to indoor and outdoor climate. The connection of a district heating system to a dehumidifier in Älta ice rink is also investigated, with the final conclusion that the amount of electricity that the system is able to save is nearly 50%. There are two different types of dehumidifiers and their energy consumption is studied and further compared with the obtained values of energy usage by the refrigeration system to dehumidify the air using the ice slab. The results show that the ice slab uses much less energy comparing with the dehumidifier system (0...

Orange fiber as a novel fat replacer in lemon ice cream

Crizel,Tainara de Moraes; Araujo,Rubilene Ramos de; Rios,Alessandro de Oliveira; Rech,Rosane; Flôres,Simone Hickmann
Fonte: Sociedade Brasileira de Ciência e Tecnologia de Alimentos Publicador: Sociedade Brasileira de Ciência e Tecnologia de Alimentos
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2014 EN
Relevância na Pesquisa
36.98%
Orange fiber was used as a novel fat replacer in light lemon ice cream. Nine ice cream formulations were compared: standard control ice cream (IC); ice cream with fiber (F1) from the peel, bagasse, and orange seed (ICA and ICB); ice cream with fiber (F2) from the orange peel alone (ICC and ICD); ice cream with fiber (F3) from the peel, bagasse, and orange seed pretreated with hydro-distillation (ICE and ICF); and ice cream with fiber (F4) from the orange peel pretreated with hydro-distillation (ICG and ICH).The orange fiber reduced the ice cream fat content (50 %) and the overrun ratio and increased the fiber content and the hardness, gumminess, and springiness values, but it did not affect the adhesiveness and odor of the samples. The samples with 1.0 % of orange fiber showed low melting rate values than those of the control ice cream. The overall acceptance of the ice cream with 1.0 % of pre-treated orange peel fiber did not differ from that of the control ice cream (80 %). The orange fiber proved a promising food ingredient since it can be used to decrease the fat content and increase bioactive compounds content, such as fiber and carotenoids.

Interaction and Variability of Ice Streams under a Triple-Valued Sliding Law and Non-Newtonian Rheology

Sayag, Roiy; Tziperman, Eli
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
37.01%
Ice streams are regions of fast flowing glacier ice that transport a significant portion of the total ice flux from present ice sheets. The flow pattern of ice streams can vary both temporally and spatially. In particular, ice streams can become stagnant and change their path. We study the dynamics of ice streams using an idealized model of an isothermal and power law viscous ice flow that includes horizontal (lateral) shear stresses. The basal sliding law is assumed to be triple-valued. We investigate the spatiotemporal patterns formed because of the flow over a flat bed, fed from an upstream mass source. The ice flows from the mass source region through one or two gaps in a prescribed upstream topographic ridge which restricts the flow, leading to the formation of one or two ice streams. We find a relation between the parameters of the ice rheology and the width of the ice stream shear margins and show how these parameters can affect the minimum width of an ice stream. We also find that complex asymmetric spatiotemporal patterns can result from the interaction of two ice streams sharing a common mass source. The rich spatiotemporal variability is found to mostly be a result of the triple-valued sliding law, but non-Newtonian effects are found to play a significant role in setting a more realistic shear margin width and allowing for relevant time scales of the variability.; Earth and Planetary Sciences

Dynamics of ice stream temporal variability: Modes, scales, and hysteresis

Robel, Alexander Abram; DeGiuli, E.; Schoof, C.; Tziperman, Eli
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.99%
Understanding the mechanisms governing temporal variability of ice stream flow remains one of the major barriers to developing accurate models of ice sheet dynamics and ice‒climate interactions. Here we analyze a simple model of ice stream hydrology coupled to ice flow dynamics and including drainage and basal cooling processes. Analytic and numerical results from this model indicate that there are two major modes of ice stream behavior: steady‒streaming and binge‒purge variability. The steady‒streaming mode arises from friction‒stabilized subglacial meltwater production, which may also activate and interact with subglacial drainage. The binge‒purge mode arises from a sufficiently cold environment sustaining successive cycles of thinning‒induced basal cooling and stagnation. Low prescribed temperature at the ice surface and weak geothermal heating typically lead to binge‒purge behavior, while warm ice surface temperature and strong geothermal heating will tend to produce steady‒streaming behavior. Model results indicate that modern Siple Coast ice streams reside in the binge‒purge parameter regime near a subcritical Hopf bifurcation to the steady‒streaming mode. Numerical experiments exhibit hysteresis in ice stream variability as the surface temperature is varied by several degrees. Our simple model simulates Heinrich event‒like variability in a hypothetical Hudson Strait ice stream including dynamically determined purge time scale...

Desenvolvimento de sorvete probiótico a base de leite de cabra: estudo da formulação, características físico químicas, sensoriais e viabilidade das bactérias probióticas; Caprine probiotic ice cream: formulation, physicalchemical and sensory characterization and viability of probiotic bacteria

Silva, Priscilla Diniz Lima da
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Química; Pesquisa e Desenvolvimento de Tecnologias Regionais Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Engenharia Química; Pesquisa e Desenvolvimento de Tecnologias Regionais
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
36.96%
This work targetet the caprine ice cream production added with probiotic bacteria Bifidobacterium animalis subsp. lactis. It is divided into two parts. In the first one, four caprine ice cream formulations were evaluated, in which it was used hydrogenated fat (F1 and F3) or fat substitute (F2 and F4) in two different flavors (F1 and F2, passion fruit, F3 and F4, guava). Statistical differences (p<0.05) were detected for their physical-chemical properties, mainly for total solids and fat, but no differences were observed for melting test results. When it went to sensory acceptance, all four ice cream formulations reached high acceptance indexes, mostly formulation F4, which was selected for further studies. In the second part, F4 formulation was prepared with the addition of probiotic bacteria Bifidobacterium animalis subsp. lactis. The growth kinetics was studied and it was observed that the cellular concentration peak was reached after four fermentation hours (10.14 log UFC/g). This time was selected for pre-fermentation procedure and posterior addition at ice cream syrup. In this part of the study, two experimental groups were evaluated: group G1, in which the probiotic addition occurred before the maturation step and group G2...

The Impact of Ice on the Agricultural Industry – Tackling Ice Use Through Workplace Initiative

Parikh, Shaneel
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Relatório
Relevância na Pesquisa
37.03%
Overall, this research paper attempts to identify and analyse how ice-use has increased over-time, and extent it has impacted the agricultural industry. Further, to assess whether mandatory drug testing could be utilised as an effective method of countering ice use within the agricultural industry. Given the 2015 Federal Government’s launch of a national taskforce to tackle ice, this project is likely to be especially relevant. Anecdotally, the impact of ice has reached and significantly impacted agricultural communities. Literature is non-existent within this sphere, therefore this research project provides perspective on the key themes surrounding ice use within the industry. Further, as mandatory drug testing has been recently considered as a potential solution to tackle ice use in the agricultural industry, given the limited literature on this topic, this project provides perspective on the viability of mandatory drug testing within the agricultural industry. The methodology throughout was mixed. Chapter One was purely a review on current literature surrounding ice in Australia. The methodology for Chapter Two was purely qualitative. It involved semi-structured interviews including 5 scaled questions, with 14 informants. The methodology for Chapter Three involved a mixture of current literature on workplace drug testing...

Numerical Modelling of Ice Microstructures; Numerische Modellierung von Mikrostrukturen in Eis

Rößiger, Jens
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
36.98%
Accurate modelling of ice mechanical behaviour under natural conditions is important for climate reconstruction and prediction, as well as for other scientific questions. It influences estimates of sea level changes and interpretation of past climate variations or signals recorded in ice cores. Better insight into the behaviour and constitutive equations of ice is imperative to improve modelling of glaciers and ice sheets. The aim of this thesis was to develop numerical models to simulate the microstructural behaviour of ice, as observed in nature and experiments. Numerical simulations were carried out with the numerical modelling platform "Elle", for which many new routines and algorithms were developed and implemented in this project. In a first series of models static grain growth and simultaneous grain-size reduction by rotational recrystallization was investigated. Well-established theory for static grain growth predicts a linear increase of the grain area with time for ice. The growth rate is then determined by the growth parameter k, which is commonly assumed to be a temperature and material-dependent constant. However, the simulations show that k also depends on the microstructure and can thus vary as the microstructure evolves. Experiments that start with non-equilibrium microstructures potentially yield growth parameters (k and the growth exponent...

Numerical simulation of deformation microstructures and folds in polar ice and ductile rocks

Llorens Verde, Maria Gema
Fonte: Universität Tübingen Publicador: Universität Tübingen
Tipo: Dissertation; info:eu-repo/semantics/doctoralThesis
EN
Relevância na Pesquisa
36.96%
This thesis contains 8 manuscripts for peer-reviewed journals (4 published, 2 submitted, 2 to be submitted within 4 weeks) that present studies of deformation microstructures and folds in polar ice and ductile anisotropic rocks by means of numerical simulations. It is organized in four different parts that focus: (1) Viscoplastic deformation of polycrystalline polar ice in simple and pure shear coupled with dynamic recrystallisation simulating microstructure evolution and formation of folds; (2) Folding and unfolding of single and multilayers in pure and simple shear; (3) Influence of anisotropy degree and type on rotation of rigid bodies (porphyroclasts and porphyroblasts); and (4) Analysis of the effects of dynamic recrystallisation on the rheology and microstructures of partially molten rocks. The first part (chapters 2, 3 and 4) contains three manuscripts analysing the influence of dynamic recrystallisation on deformation of pure polar ice. A full-field viscoplastic code (FFT) that fully reproduces the ice crystal’s mechanical anisotropy is coupled with dynamic recrystallisation processes to perform a series of numerical simulations in pure (chapter 2) and in simple shear (chapter 3 and 4). The results show that dynamic recrystallisation (DRX) has remarkable effects on the developed ice microstructures...

A comparison of ice drift motion from modeled and buoy data

Lundeen, Gregory N.
Fonte: Monterey, California: Naval Postgraduate School Publicador: Monterey, California: Naval Postgraduate School
Tipo: Tese de Doutorado Formato: ix, 113 p., maps
EN_US
Relevância na Pesquisa
37%
Approved for public release; distribution is unlimited.; U.S. Naval operations in the Arctic require an effective way to predict the movement and behavior of sea ice. This is currently provided by the Navy's PIPS model which is based on Hibler's (1979) sea ice model which combines the thermodynamic ice heat budget with a dynamic ice model sensitive to the effects of ice thickness and ice strength. The PIPS model simultaneously solves a system of four equations of ice momentum balance, ice rheology, ice thickness, and ice strength. In order to test the performance of Hibler's formulation, another version of it, developed by Lemke et al., (1990), was adapted to the Arctic Ocean. The model was initialized and run using 1986 forcing data and its performance evaluated using Arctic buoy drift data. Results indicate that the model ice drift is principally driven by wind forcing, that its response to changes in weather is rapid and essentially correct, and that it performs better at high wind speeds than at low wind speeds. Limitations to its accuracy were chiefly the result of limits to the precision and resolution of the input data provided to run the model, especially near the ice margins. Overall, the model performs well in depicting the ice flow pattern in all conditions in the Arctic.; Lieutenant...

A review of sea ice proxy information from polar ice cores

Abram, Nerilie J; Wolff, Eric W; Curran, Mark A J
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica Formato: 16 pages
Relevância na Pesquisa
37.05%
Sea ice plays an important role in Earth’s climate system. The lack of direct indications of past sea ice coverage, however, means that there is limited knowledge of the sensitivity and rate at which sea ice dynamics are involved in amplifying climate changes. As such, there is a need to develop new proxy records for reconstructing past sea ice conditions. Here we review the advances that have been made in using chemical tracers preserved in ice cores to determine past changes in sea ice cover around Antarctica. Ice core records of sea salt concentration show promise for revealing patterns of sea ice extent particularly over glacialeinterglacial time scales. In the coldest climates, however, the sea salt signal appears to lose sensitivity and further work is required to determine how this proxy can be developed into a quantitative sea ice indicator. Methane sulphonic acid (MSA) in near-coastal ice cores has been used to reconstruct quantified changes and interannual variability in sea ice extent over shorter time scales spanning the last w160 years, and has potential to be extended to produce records of Antarctic sea ice changes throughout the Holocene. However the MSA ice core proxy also requires careful site assessment and interpretation alongside other palaeoclimate indicators to ensure reconstructions are not biased by non-sea ice factors...

Ice Association in Microbes

WILSON, Sandra
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.99%
Microbes have a remarkable ability to adapt to a host of environmental stressors, including low temperature, high pressure and osmotic stresses. The adaptations of resistant microbes to low temperatures are varied, and may include the accumulation of solutes to maintain osmotic balance, the production of antifreeze proteins (AFPs) or ice nucleation proteins (INPs) to manipulate ice growth or formation. AFPs depress the freezing point, inhibit ice recrystallization, and have been reported to inhibit or delay the growth of gas hydrates. Conversely, INPs precipitate ice formation at relatively high subzero temperatures. Collectively, these activities can be described as ‘ice-association’ activities. Here, ice-affinity and/or freeze-thaw cycling were used to either select for isolates with ice association properties or to assess the low temperature resistance of microbial consortia derived from various environments. Ice-affinity successfully selected psychrotolerant microbes from cultured temperate and boreal soils, some of which had been previously reported in glaciers and Arctic/Antarctic sites. Many of the recovered microbes demonstrated ice-association activities. Freeze-thaw selection also greatly decreased the abundance and diversity of consortia from distinct sites...

Cenozoic ice sheet history from east Antarctic Wilkes Land continental margin sediments.

Escutia, Carlota; De Santis, L.; Donda, F.; Dunbar, R.B.; Cooper, A.K.; Brancolini, G.; Eittreim, S.L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 10752 bytes; application/octet-stream
ENG
Relevância na Pesquisa
36.98%
10 figures, 3 tables.; The long-term history of glaciation along the East Antarctic Wilkes Land margin, from the time of the first arrival of the ice sheet to the margin, through the significant periods of Cenozoic climate change is inferred using an integrated geophysical and geological approach. We postulate that the first arrival of the ice sheet to the Wilkes Land margin resulted in the development of a large unconformity (WL-U3) between 33.42 and 30 Ma during the early Oligocene cooling climate trend. Above WL-U3, substantial margin progradation takes place with early glacial strata (e.g., outwash deposits) deposited as low-angle prograding foresets by temperate glaciers. The change in geometry of the prograding wedge across unconformity WL-U8 is interpreted to represent the transition, at the end of the middle Miocene “climatic optimum” (14–10 Ma), from a subpolar regime with dynamic ice sheets (i.e., ice sheets come and go) to a regime with persistent but oscillatory ice sheets. The steep foresets above WL-U8 likely consist of ice proximal sediments (i.e., water-lain till and debris flows) deposited when grounded ice-sheets extended into the shelf. On the continental rise, shelf progradation above WL-U3 results in an up-section increase in the energy of the depositional environment (i.e....

The influence of subglacial hydrology on the flow of West Antarctic ice streams

Baker, Narelle Paula Marie
Fonte: University of Cambridge; Scott Polar Research Institute; Trinity College Publicador: University of Cambridge; Scott Polar Research Institute; Trinity College
Tipo: Thesis; doctoral; PhD
EN
Relevância na Pesquisa
37.03%
Subglacial hydrology is known to influence the flow of ice. However, difficulty in accessing the base of large ice sheets has made determining the interaction between ice streams, basal sediment and water difficult to discern. The aim of this thesis is to determine the influence of subglacial hydrology on the flow of the West Antarctic ice streams. This is achieved through development of a numerical flowline model, the Hydrology, Ice and Till (HIT) model. Ice thermodynamics are coupled to a till layer of Coulomb plastic rheology. The porosity of the till changes with basal melt and freeze and can be augmented by water transported through a subglacial conduit system. Water availability strongly affects ice flow, as till porosity influences the till failure strength and thereby the basal resistance of the ice. The model was developed in four stages and a number of sensitivity tests were performed. It was then applied to Kamb Ice Stream (Ice Stream C) and Whillians Ice Stream (Ice Stream B), West Antarctica. Results confirm that ice streams are capable of oscillating between fast and slow velocity states. Cycles are generated at the grounding line of an ice stream and the speed of the transition from slow to fast flow is governed by water availability. The period of oscillation of the cycles for the West Antarctic ice streams was found to be several hundred years...

Sea ice thickness and the distribution contributing to the mass balance of the Southern Ocean

Bernstein, Elizabeth Rachel
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
37.03%
Geiger, Cathleen; Although sea ice concentration, extent, and type can be measured with acceptable accuracy by satellite or airborne remote sensing techniques, sea ice thickness measurements are difficult to obtain accurately, even in situ. Modeling sea ice volume and associated transport requires input data for ice motion, as well as for the distribution of sea ice thickness. There is a need to develop new sea ice models driven by the best available data. The majority of sea ice thickness measurements in the Southern Ocean are derived from drill holes, and more recently upward looking sonar and electromagnetic methods, but these data points are sparse. The most comprehensive sea ice thickness dataset for Antarctic sea ice available to date is the Antarctic Sea Ice Processes and Climate (ASPeCt) program, which includes 23,373 ship-based observations collected over two decades; however, this dataset has spatial and temporal gaps. This thesis uses the ice stage of development records from National/Naval Ice Center (NIC) operational ice charts as a proxy for sea ice thickness from four years (1995-1998). From the sea ice information within the ice charts, ice thickness and volume are derived to produce model-input-ready Southern Ocean sea ice thickness distributions on multiple temporal and regional scales. Evaluation of the basin-wide thickness distribution includes analysis of multiple sea ice thickness calculation methods and an examination of the seasonal and regional patterns of sea ice distribution.; University of Delaware...

The effects of atmospheric and oceanic conditions on the stability of ice bridges

Stelma, Sigourney Anne
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
Relevância na Pesquisa
37.01%
Huntley, Helga; Ice bridges are arch-like ice structures that form in narrow passages and straits. These bridges play largely important roles in the circulation of Arctic sea ice. When an ice bridge is present in a strait, there is typically a stoppage of sea ice flow, and there generally little ice flow downstream from the bridge. Nares Strait, located between Ellesmere Island and Greenland, allows for Arctic sea ice to be exported into the Atlantic Ocean. Ice bridges typically form in Nares Strait, which causes a stoppage of this export. This stoppage allows for Arctic sea ice to grow thicker, which is important for our current climate. Building on studies that examined the formation of ice bridges, this study aims to model and analyze the destruction of ice bridges. Using CICE: The Los Alamos Sea Ice Model, ice bridges are modeled in an idealized strait that is geographically and dimensionally similar to Nares Strait. The bridges are allowed to strengthen for 7 days past their initial formation. Then various atmospheric and oceanic parameters are changed, to examine their effect on the stable ice bridges. All parameter changes are applied over the entire domain and are constant in time. Extreme temperatures are used to study the effect of temperature. Then various amounts of longwave and shortwave radiation are tested independently...

Year-round pack ice in the Weddell Sea, Antarctica: Response and sensitivity to atmospheric and oceanic forcing

Geiger, Cathleen A.; Ackley, Stephen F.; Hibler, M. D.
Fonte: International Glaciology Society Publicador: International Glaciology Society
Tipo: Artigo de Revista Científica
ENGLISH (UNITED STATES)
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Final published version; Using a dynamic-thermodynamic numerical sea-ice model, external oceanic and atmospheric forcings on sea ice in the Weddell Sea are examined to identify physical processes associated with the seasonal cycle of pack ice, and to identify further the parameters that coupled models need to consider in predicting the response of the pack ice to climate and ocean-circulation changes. In agreement with earlier studies, the primary influence on the winter ice-edge maximum extent is air temperature. Ocean heat flux has more impact on the minimum ice-edge extent and in reducing pack-ice thickness, especially in the eastern Weddell Sea. Low relative humidity enhances ice growth in thin ice and open-water regions, producing a more realistic ice edge along the coastal areas of the western Weddell Sea where dry continental air has an impact. The modeled extent of the Weddell summer pack is equally sensitive to ocean heat flux and atmospheric relative humidity variations with the more dynamic responses being from the atmosphere. Since the atmospheric regime in the eastern Weddell is dominated by marine intrusions from lower latitudes, with high humidity already, it is unlikely that either the moisture transport could be further raised or that it could be significantly lowered because of its distance from the continent (the lower humidity source). Ocean heat-transport variability is shown to lead to overall ice thinning in the model response and is a known feature of the actual system...