Дисертації з теми "Glacial ice flow"
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Stokes, Christopher Richard. "The geomorphology of palaeo-ice streams : identification, characterisation and implications for ice stream functioning." Thesis, University of Sheffield, 2001. http://etheses.whiterose.ac.uk/14815/.
Повний текст джерелаWalden, John. "The use of mineral magnetic analysis in the study of glacial diamicts." Thesis, University of Wolverhampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259185.
Повний текст джерелаFairman, Jonathan George. "Investigating paleoclimatic conditions in the tropical Andes using a 2-D model of glacial mass energy balance and ice flow /." Connect to resource, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1211912269.
Повний текст джерелаFairman, Jonathan George Jr. "Investigating Paleoclimatic Conditions in the Tropical Andes Using A 2-D Model of Glacial Mass Energy Balance and Ice Flow." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1211912269.
Повний текст джерелаAllen, Simon Keith. "Geomorphic Hazards associated with Glacial Change, Aoraki/Mount Cook region Southern Alps, New Zealand." Thesis, University of Canterbury. Geography, 2009. http://hdl.handle.net/10092/3087.
Повний текст джерелаCallens, Denis. "Impact of improved basal and surface boundary conditions on the mass balance of the Sr Rondane Mountains glacial system, Dronning Maud Land, Antarctica." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209217.
Повний текст джерелаIn this thesis, we assess the mass balance of a part of eastern DronningMaud Land via an input/output method. Input is given by recent surface accumulation estimations of the whole drainage basin. The outflow at the grounding line is determined from the radar data of a recent airborne survey and satellite-based velocities using a flow model of combined plug flow and simple shear. We estimate the regional mass balance in this area to be between 1.88±8.50 and 3.78±3.32 Gt a−1 depending on the surface mass balance (SMB) dataset used. This study also reveals that the plug flow assumption is acceptable at the grounding line of ice streams.
The mass balance of drainage basins is governed by the dynamics of their outlet glaciers and more specifically the flow conditions at the grounding line. Thanks to an airborne radar survey we define the bed properties close to the grounding line of the West Ragnhild Glacier (WRG) in the Sør Rondane Mountains. Geometry and reflectivity analyses reveal that the bed of the last 65 km upstream of the grounding line is sediment covered and saturated with water. This setting promotes the dominance of basal motion leading to a change in the flow regime: in the interior flow is governed by internal deformation while its relative importance decreases to become driven by basal sliding.
Subsequently we present the results of the reconstruction of the SMB across an ice rise through radar data and inverse modelling. The analysis demonstrates that atmospheric circulation was stable during the last millennium. Ice rises induce an orographic uplift of the atmospheric flow and therefore influence the pattern of the SMB across them, resulting in an asymmetric SMB distribution. Since the geometry of the internal reflection horizons observed in radar data depends on the SMB pattern, the asymmetry observed in radar layers reveals the trajectories of air masses at the time of deposit. We present an original and robust method to quantify this SMB distribution. Combining shallow and deep radar layers, SMB across Derwael Ice Rise is reconstructed. Two methods are employed as a function of the depth of the layers: i.e. the shallow layer approximation for the surface radar layers and an optimization technique based on an ice flow model for the deeper ones. Both methods produce similar results. We identify a difference in SMB magnitude of 2.5 between the flanks and the ice rise divide, as well as a shift of ≈4 km between the SMB maximum and the crest. Across the ice rise, SMB exhibits a very large variability, ranging from 0.3 to 0.9 mw.e. a−1. This anomaly is robust in time.
Finally we draw a comprehensive description of the Sør Rondane Mountains sector. The glacial system is close to the equilibrium and seems stable but evidences suggest that it is a fragile equilibrium. The proximity of the open ocean certainly favours the interaction between warm water and the ice shelf cavity conducting to potential important melting. The thinning associated with this melting can detach the ice shelf from pinning points. This will reduce the buttressing from the ice shelf, outlet glaciers will accelerate and mass transfer toward the ocean will increase. Therefore, the future of Antarctic Ice Sheet directly depends on the changes affecting its boundaries and assessing the sensitivity of the ice sheets is essential to quantify and anticipate the future variation of mass balance.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
Watts, Leonard Gary. "Finite element simulations of ice mass flow." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276336.
Повний текст джерелаVallin, Sara. "LiDAR-bildanalys av flutings i södra Norrbotten : Kartering och datering av avvikande isrörelseriktningar." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-96181.
Повний текст джерелаLeighton, Iain Douglas Leighton. "Identifying fast glacier flow : the sedimentological and micromorphological signature of surges and ice streams." Thesis, Swansea University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678503.
Повний текст джерелаHedfors, Jim. "Force Budget Analysis of Glacier Flow : Ice Dynamical Studies on Storglaciären, Sweden, and Ice Flow Investigations of Outlet Glaciers in Dronning Maud Land, Antarctica." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4219.
Повний текст джерелаThis thesis contributes to the understanding of glacier response to climate change by ice dynamical studies on Storglaciären, Sweden, and Bonnevie-Svendsenbreen, Kibergbreen and Plogbreen in Dronning Maud Land, Antarctica. Ice surface velocities, ice geometry and temperature information is fed through a force budget model to calculate ice mass outflux of these glacial systems via three-dimensional stress distributions for a flux-gate.
Field data were collected through repeated DGPS and GPR observations on Storglaciären between July 2000 to September 2001 and on Kibergbreen and Plobreen during the SWEDARP 2002/03 expedition to Antarctica. The work was strongly supported by remotely-sensed information.
The results from Storglaciären show a strength in the force budget model to discern both spatial and temporal variability in ice dynamical patterns. It highlights the influence of seasonality and bedrock topography upon glacier flow. A modeling experiment on Bonnevie-Svendsenbreen suggested that ice temperature increases substantially under conditions of high stress (≥0.4 MPa) due to strain-heating. This provides a positive feedback loop, increasing ice deformation, as long as it overcomes the advection of cool ice from the surface. These results explain, to some extent, the mechanism behind fast flowing ice streams. Mass flux caclulations from Bonnevie-Svendsenbreen suggest that the outflux given from force budget calculations can be used as a gauge for influx assuming steady state conditions. Plogbreen receives an influx of 0.48±0.1 km3 a-1 and expedites a discharge volume of 0.55±0.05 km3 a-1. This indicative negative mass balance is explained by a falling trend in upstream accumulation and the recent rise in global sea level, as it is likely to induce glacier acceleration due to a reduction in resistive forces at the site of the gate. This result is comparable with other Antarctic studies reporting negative mass balances, e.g. from WAIS, as caused by changes in the global atmospheric circulation pattern.
Moore, Peter L. "Dynamics of ice flow and sediment transport at a polythermal glacier terminus: Storglaciaren, Sweden." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3369867.
Повний текст джерелаLelandais, Thomas. "Modélisation analogique des écoulements d'eau sous-glaciaire : implications sur les relations entre vallées tunnels et dynamique glaciaire." Thesis, Le Mans, 2018. http://www.theses.fr/2018LEMA1022/document.
Повний текст джерелаTunnel valleys are major components of the subglacial meltwater drainage system. The inaccessibility of modern subglacial environments reduces our knowledge on the mechanisms involved in tunnel valleys formation, the parameters controlling their morphology and their influence on ice-sheet dynamics. This work presents a new experimental approach aiming to better assess the processes of tunnel valleys development. This approach relies on the development of a new experimental device simulating a pressurized water flow within a porous and permeable substratum underneath a viscous layer simulating the ice-sheet. The main results of the experiments conducted with this device have demonstrated the influence of both substratum properties and meltwater drainage on tunnel valleys formation and morphology. Using the device, we first manage to reproduce tunnel valley systems experimentally. Analyses conducted on these valleys experimental valleys suggest that the substratum topography and meltwater production play a key role on tunnel valleys genesis and morphology. Two tunnel valleys morphotypes have been identified, each one being charaterized by a unique morphology and mechanism of formation. Monitoring of the experimental ice sheet during tunnel valley formation shows close relationship between tunnel valleys development and "ice streams" dynamics. The evolution of tunnel valley drainage capacity seems to have a strong influence on ice sheet stability by regulating ice flux within "ice stream corridors"
Enderlin, Ellyn Mary. "Observations and Modeling of Greenland Outlet Glacier Dynamics." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372609057.
Повний текст джерелаLicciulli, Carlo [Verfasser], and Olaf [Akademischer Betreuer] Eisen. "Full Stokes ice-flow modeling of the high-Alpine glacier saddle Colle Gnifetti, Monte Rosa: Flow field characterization for an improved interpretation of the ice-core records / Carlo Licciulli ; Betreuer: Olaf Eisen." Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177691256/34.
Повний текст джерелаDehecq, Amaury. "Analyse de la dynamique des glaciers himalayens et alpins à partir de 40 ans de données d’observation de la Terre." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAA027/document.
Повний текст джерелаMountain glaciers have a high societal impact, first at a local scale since they influence the water ressources and the touristic attractivity of a region, but also at a global scale, being major contributors to the present sea-level rise. Moreover, mountain glaciers are sensitive to climate forcing and are thus relevant indicators of past and present climate change and particularly present global warming. It is thus important to analyse the dynamic of these glaciers and quantify the changes that are affecting them so that their contribution to the Earth system and their future evolution can be better estimated. Satellite Earth Observation imagery, with its global coverage and repeated acquisition, represents a unique tool to quantify temporal changes affecting glaciers. The available archive is huge and the flux of new data will increase it even more.It is thus necessary to develop new methods to process this large archive.The objective of this thesis is to quantify the dynamic response of mountain glaciers in the Pamir-Karakoram-Himalaya (PKH) and in the Alps to a changing climate, with the use of the 40-year long satellite archive. We first developped a semi-automated processing chain to derive annual ice flow velocities from feature-tracking of satellite images. The chain takes advantage of the redundancy in the archive to obtain more spatially complete and robust velocity fields and to statistically estimate the uncertainty. Application to the Landsat archive leads to the determination of an unprecedented velocity field for the entire PKH region (~92 000 km2) for the period 1998-2014 and over the Alps (2 000 km2, period 1999-2014) with a coverage of 60-80 % and a mean uncertainty of 4 m/yr.. Flow velocities have been derived less systematically for the period 1972-1998 over the PKH. Secondly, the analysis of velocity changes show a slow-down of the glaciers for most of the 2 regions. The velocity changes are spatially contrasted and coherent with the patterns of elevation changes. In particular, glaciers in the Karakoram and West Kunlun that are stable or advancing show also a clear speed-up, whereas regions where thinning is the most important (Western Himalaya, Nyenchen Tangla, Alps) show the most important slow-down. The observed velocity changes is thus primarily determined by a climatic signal
Pomeroy, Joseph Anthony. "The sedimentary and geomorphic signature of subglacial processes in the Tarfala Valley, northern Sweden, and the links between subglacial soft-bed deformation, glacier flow dynamics, and landform generation." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13647.
Повний текст джерелаVallot, Dorothée. "Modelling calving and sliding of Svalbard outlet glaciers : Spatio-temporal changes and interactions." Doctoral thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-334787.
Повний текст джерелаBäßler, Michael. "Untersuchungen zu Topographie und Bewegungsverhalten für das Küstengebiet des Riiser-Larsen- und Brunt-Schelfeises mittels Radarfernerkundung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-70201.
Повний текст джерелаThe development of new satellite sensors within the last 20 years along with changes towards more sophisticated processing strategies has not only given a new impetus to remote sensing data in view of polar research but also changed how a variety of glaciological problems are being addressed today. Particularly RADAR (radio detection and ranging) sensors are well-suited for the observation of glaciated areas and have already helped to retrieve a vast amount of climate sensitive parameters from the area of Antarctica. After an introductive overview at the beginning, the second chapter continues with the description of how RADAR measurements can be used to generate remote sensing images. The principle of synthetic aperture RADAR (SAR) which allows a better focusing of the RADAR measurements and therewith a rigorous increase of the spatial resolution of the images is outlined generally before more precise descriptions explain how interferometric SAR (InSAR) analyses can be used for the determination of surface topography heights and area-wide flow velocities. Two other techniques, namely matching methods for the determination of shifts between two images as well as the laser satellite altimetry are explained at the end of this chapter which closes the theoretical basics. The next section introduces the area of interest along with data sets which were used for validation purposes. After a careful exposure of the geographical situation, single objects such as ice streams and ice shelves are described in more detail. The following part, the data set introduction, has besides the description of other measurements its focus on topography and ocean tide models which are available for the area of investigation. Chapter four deals with the estimation of surface topography heights from differential InSAR (DInSAR) analyses. Therein the major differences for the usage of similar repeat tracks in contrast to neighboring, overlapping tracks will be shown and thoroughly discussed. The example of one track will be used to demonstrate how the required baseline estimation can be achieved if ICESat (Ice, Cloud and Land Elevation Satellite) profiles are used as tie points. Afterwards, all separately derived height models will be combined to obtain one final solution followed by an error analysis. A comparison to other available elevation models visualizes the spatial resolution of the derived model. The utilization of three different methods for the estimation of surface flow velocities (with the background of possible mass flux determinations) is the topic of the fifth chapter. The first case describes the usage of the high frequent noise contained in RADAR images for the tracking of horizontal surface displacements. Based on ALOS (Advanced Land Observing Satellite) data a flow velocity field which extends from the interior of the ice sheet across the grounding zone up to the ice shelf will be presented. Secondly, geocoded ERS (European Remote Sensing Satellite) images covering a time span of more than 13 years are used to track the motions of well-structured flat areas (ice shelf and glacier tongue). In the third approach used descending and ascending satellite passes will be combined in conjunction with a surface parallel flow assumption to interferometrically derive flow velocities in grounded areas. In each section respective errors will be discussed in order to evaluate the accuracy of the performed measurements. The last bigger chapter, number six, is divided into two sections. In the first one the adoption of SAR and InSAR with respect to the mapping of the grounding line location will be demonstrated. Results of the entire working area will be presented and compared to other data. The second section deploys the results of topography heights and flow velocities to remove both effects from the InSAR measurements which then allows to also measure height changes. This is of particular interest for the floating areas of ice shelf which are fully affected by ocean tides as well as for the grounding zone locations which partially experience deformations due to these height changes. After the correction for air pressure, changes between the image acquisitions, height changes along selected profiles are compared to twelve different ocean tide models. The RMS values of the differences are then used to evaluate the quality of these models for the working area. The most important results and conclusions are summarized in the last chapter
Marchenko, Sergey. "Subsurface fluxes of mass and energy at the accumulation zone of Lomonosovfonna ice cap, Svalbard." Doctoral thesis, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-334178.
Повний текст джерелаStability and Variations of Arctic Land Ice (SVALI)
Bäßler, Michael. "Untersuchungen zu Topographie und Bewegungsverhalten für das Küstengebiet des Riiser-Larsen- und Brunt-Schelfeises mittels Radarfernerkundung: Untersuchungen zu Topographie und Bewegungsverhalten für das Küstengebiet des Riiser-Larsen- und Brunt-Schelfeises mittels Radarfernerkundung." Doctoral thesis, 2010. https://tud.qucosa.de/id/qucosa%3A25606.
Повний текст джерелаThe development of new satellite sensors within the last 20 years along with changes towards more sophisticated processing strategies has not only given a new impetus to remote sensing data in view of polar research but also changed how a variety of glaciological problems are being addressed today. Particularly RADAR (radio detection and ranging) sensors are well-suited for the observation of glaciated areas and have already helped to retrieve a vast amount of climate sensitive parameters from the area of Antarctica. After an introductive overview at the beginning, the second chapter continues with the description of how RADAR measurements can be used to generate remote sensing images. The principle of synthetic aperture RADAR (SAR) which allows a better focusing of the RADAR measurements and therewith a rigorous increase of the spatial resolution of the images is outlined generally before more precise descriptions explain how interferometric SAR (InSAR) analyses can be used for the determination of surface topography heights and area-wide flow velocities. Two other techniques, namely matching methods for the determination of shifts between two images as well as the laser satellite altimetry are explained at the end of this chapter which closes the theoretical basics. The next section introduces the area of interest along with data sets which were used for validation purposes. After a careful exposure of the geographical situation, single objects such as ice streams and ice shelves are described in more detail. The following part, the data set introduction, has besides the description of other measurements its focus on topography and ocean tide models which are available for the area of investigation. Chapter four deals with the estimation of surface topography heights from differential InSAR (DInSAR) analyses. Therein the major differences for the usage of similar repeat tracks in contrast to neighboring, overlapping tracks will be shown and thoroughly discussed. The example of one track will be used to demonstrate how the required baseline estimation can be achieved if ICESat (Ice, Cloud and Land Elevation Satellite) profiles are used as tie points. Afterwards, all separately derived height models will be combined to obtain one final solution followed by an error analysis. A comparison to other available elevation models visualizes the spatial resolution of the derived model. The utilization of three different methods for the estimation of surface flow velocities (with the background of possible mass flux determinations) is the topic of the fifth chapter. The first case describes the usage of the high frequent noise contained in RADAR images for the tracking of horizontal surface displacements. Based on ALOS (Advanced Land Observing Satellite) data a flow velocity field which extends from the interior of the ice sheet across the grounding zone up to the ice shelf will be presented. Secondly, geocoded ERS (European Remote Sensing Satellite) images covering a time span of more than 13 years are used to track the motions of well-structured flat areas (ice shelf and glacier tongue). In the third approach used descending and ascending satellite passes will be combined in conjunction with a surface parallel flow assumption to interferometrically derive flow velocities in grounded areas. In each section respective errors will be discussed in order to evaluate the accuracy of the performed measurements. The last bigger chapter, number six, is divided into two sections. In the first one the adoption of SAR and InSAR with respect to the mapping of the grounding line location will be demonstrated. Results of the entire working area will be presented and compared to other data. The second section deploys the results of topography heights and flow velocities to remove both effects from the InSAR measurements which then allows to also measure height changes. This is of particular interest for the floating areas of ice shelf which are fully affected by ocean tides as well as for the grounding zone locations which partially experience deformations due to these height changes. After the correction for air pressure, changes between the image acquisitions, height changes along selected profiles are compared to twelve different ocean tide models. The RMS values of the differences are then used to evaluate the quality of these models for the working area. The most important results and conclusions are summarized in the last chapter.