• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 20
  • 3
  • 1
  • 1
  • Tagged with
  • 27
  • 7
  • 7
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Crevassing and calving of glacial ice /

Kenneally, James Patrick. January 2003 (has links) (PDF)
Thesis (Ph. D.) in Physics--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 111-116).
2

Crevassing and Calving of Glacial Ice

Kenneally, James Patrick January 2003 (has links) (PDF)
No description available.
3

Iceberg stability and deterioration /

Liang, Bo, January 2001 (has links)
Thesis (M.Eng.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 99-102.
4

Ice-atmosphere interactions in the Canadian High Arctic

Wohlleben, Trudy M. H. January 1900 (has links)
Thesis (Ph. D.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on August 26, 2009). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Dept. of Earth and Atmospheric Sciences, University of Alberta. Includes bibliographical references.
5

Hydrodynamic interactions between ice masses and large offshore structures

Cheung, Kwok Fai January 1987 (has links)
The objective of the work described in this thesis is to evaluate the significance of the ambient fluid on the motion of an ice mass in the vicinity of an offshore structure and during the subsequent impact mechanism. Models for iceberg drift are first reviewed. The changes in flow field around an ice mass drifting in a current near an offshore structure are investigated by potential flow theory. The proximity effects and current interactions are generalized by introducing the added mass and convective force coefficients for the ice mass. A two-dimensional numerical model based on the boundary element method is developed to calculate these coefficients over a range of separation distances up to the point of contact. A numerical model based on ice properties and geometry is developed to simulate the impact force acting on the structure. Both the 'contact-point' added masses estimated in this thesis and the traditionally assumed far-field added masses are used in the impact model separately. The results from the two cases are compared and the crucial roles played by the ambient fluid during impact are discussed. Finally, a number of related topics is proposed for further studies. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate
6

Application of the Kalman filter to iceberg motion forecating

Simon, Christophe January 1990 (has links)
The objective of this study is to develop an application of the Kalman filter for filtering and forecasting iceberg positions and velocities in order to calculate the risk of impact against a fixed structure or stationary vessel. Existing physical and probabilistic models are reviewed. Physical models are essentially based on the response of the iceberg to the forces acting on it. Statistical models forecast the motion of the iceberg based on past observations of the trajectory. A probabilistic iceberg trajectory model is used in this study so that uncertainties in the trajectory forecast can be explicitly included. The technique of Kalman filtering is described and applied to forecast future positions and velocities of an ice feature, including uncertainties.The trajectory forecast combined with a risk calculation, yields the probability of impact and the probability distribution of the time until impact. Numerical simulations are provided to demonstrate and validate the procedure. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate
7

Analyse et modélisation des ondes sismiques générées lors des séismes glaciaires induits par le vêlage d'icebergs / Analysis and modelling of seismic waves generated by glacial earthquakes and iceberg calving

Sergeant, Amandine 16 November 2016 (has links)
Les séismes glaciaires ont des magnitudes Mw~5 et sont liés au vêlage d’icebergs instables volumineux (km3). Dans le but de caractériser la force à l’origine des signaux sismiques longue-période (10-100~s) mesurés lors de tels évènements, nous développons une méthode d’inversion de la fonction source et un modèle mécanique numérique du phénomène. Grâce à l’analyse détaillée des histoires de forces inversées, nous mettons en lumière l’existence de plusieurs phénomènes responsables de la génération du signal sismique, à savoir (1) une avalanche de glace déclenchée par le détachement d’un iceberg, (2) le vêlage et le basculement de l’iceberg qui applique une force horizontale normale au glacier, et (3) l’accélération de l’ice-mélange dans le fjord. On montre que la magnitude des séismes glaciaires ne peut être interprétée de manière simple car elle englobe plusieurs processus distincts. D’après les résultats de modélisation numérique, l’amplitude de la force générée par un iceberg tournant contre un terminus ne varie pas de manière linéaire avec le volume de glace mais est largement déterminée par plusieurs facteurs qui influent sur la dynamique du mouvement. Ceci démontre que, l’estimation de la perte de glace lors des séismes glaciaires ne semble pas évidente à partir de leur magnitude. La comparaison des forces inversées et modélisées montre que nous sommes capables de reproduire les signaux sismiques et d’accéder ainsi à la dynamique du phénomène. Les informations contenues dans les variations temporelles de la force de vêlage permettent notamment d’inverser chaque paramètre individuel du modèle et d’estimer ainsi les dimensions et le volume de glace détaché / Glacial earthquakes have magnitudes Mw~5 and associated to the calving of large-scale (km3) unstable icebergs. In order to characterize the force at the origin of long-period seismic signals (10-100~s), we develop a source inversion scheme and a numerical modeling of iceberg capsize. Thanks to detailed analysis of the inverted force histories, we reveal the existence of several phenomena responsible for the seismic signal generation, being (1) an ice-avalanche triggered by the detachment of a first iceberg, (2) the calving and capsize of icebergs which apply a horizontal force normal to the glacial terminus, and (3) the ice-melange acceleration in the fjord. This shows that the interpretation to the event magnitudes is not straightforward as they represent the energy that is released by distinct mechanisms. With mechanical numerical modeling of the phenomenon, we show that the force amplitude does not linearly scales with the iceberg volume but also depends on various parameters that control capsize dynamics. This implies that the calving-induced mass loss cannot be estimated from the glacial earthquake magnitude only. Nevertheless, by comparing between seismic inverted forces and the modeling results, we are able to reproduce seismic signals and access the event dynamics. Informations that are contained in the force histories enable to invert each model parameter and thus estimate the iceberg dimensions and then volume
8

Using multiple agents in uncertainty minimization of ablating target sources

Coogle, Richard A. 12 January 2015 (has links)
The objective of this research effort is to provide an efficient methodology for a multi-agent robotic system to observe moving targets that are generated from an ablation process. An ablation process is a process where a larger mass is reduced in volume as a result of erosion; this erosion results in smaller, independent masses. An example of such a process is the natural process that gives rise to icebergs, which are generated through an ablation process referred to as ice calving. Ships that operate in polar regions continue to face the threat of floating ice sheets and icebergs generated from the ice ablation process. Although systems have been implemented to track these threats with varying degrees of success, many of these techniques require that the operations are conducted outside of some boundary where the icebergs are known not to drift. Since instances where polar operations must be conducted within such a boundary line do exist (e.g., resource exploration), methods for situational awareness of icebergs for these operations are necessary. In this research, efficacy of these methods is correlated to the initial acquisition time of observing newly ablated targets, as it provides for the ability to enact early countermeasures. To address the research objective, the iceberg tracking problem is defined such that it is re-cast within a class of robotic, multiagent target-observation problems. From this new definition, the primary contributions of this research are obtained: 1) A definition of the iceberg observation problem that extends an existing robotic observation problem to the requirements for the observation of floating ice masses; 2) A method for modeling the activity regions on an ablating source to extract ideal search regions to quickly acquire newly ablated targets; 3) A method for extracting metrics for this model that can be used to assess performance of observation algorithms and perform resource allocation. A robot controller is developed that implements the algorithms that result from these contributions and comparisons are made to existing target acquisition techniques.
9

Iceberg Production and Characteristics at the Termini of Tidewater Glaciers around the Prince of Wales Icefield, Ellesmere Island

Dalton, Abigail January 2017 (has links)
Since the 1960s, warming air and sea surface temperatures have led to decreasing sea ice extent and longer periods of open water in the Canadian Arctic Archipelago (CAA). Recent and rapid changes have also been observed in the ice discharge patterns of glaciers in this region. For example, Trinity and Wykeham glaciers on the Prince of Wales Icefield (POW), SE Ellesmere Island, contributed ~62% of total ice discharge to the ocean from the Canadian Arctic Archipelago in 2016, compared to ~22% in 2000. Given these changes, an important question is whether there is a relationship between changing sea ice conditions (e.g., extent, freeze up dates, break up dates) and iceberg production from these glaciers. This study used synthetic aperture radar (Radarsat-1, 2 and ALOS PALSAR) and optical (Landsat-7 and 8) imagery to identify iceberg plume events and sea ice break-up/freeze-up dates between 1997 and 2015 for 40 tidewater glaciers around the POW. Results show a clear relationship between the presence of sea ice and the production of icebergs from glaciers, with most events occurring during the open water season and fewer when sea ice was present. While there have not been clear increasing trends of icebergs produced from all glaciers in the POW, Trinity and Wykeham glaciers show that increases in detected iceberg plumes coincide with increases in previously measured glacier velocity and significant terminus retreat. Comparison to ocean temperature, surface air temperature from NCEP/NCAR reanalysis and tidal data showed no clear relationship with increased calving events, however further research into all factors is recommended. It is likely that there are several factors contributing to the spatial and temporal variability of iceberg production from the POW.
10

Monitoring Fjord Circulation Using Iceberg-Mounted GPS as Real-Time Drifters

Roth, George 29 September 2014 (has links)
Ocean circulation in Greenland's large glacial fjords is one mechanism that controls the rate of submarine melting at the termini of Greenland's outlet glaciers. Here we use hourly position data from GPS units deployed on ten large (>100 meter), deep-keeled icebergs in Sermilik Fjord, SE Greenland. We observe and quantify the motions of these icebergs moving through the mélange, fjord, and shelf regimes. In the mélange, icebergs move outward with glacier flow until pushed loose by large calving events. In the fjord, high frequency, low amplitude tidally-driven motions are superimposed on dominant 1-5 day events with net velocities exceeding 0.1 m/s. We interpret these events as two-layer, intermediary circulation driven by winds along the shelf, where icebergs travel southward in the East Greenland Coastal Current. These results showcase the potential of this novel instrumentation to link iceberg motion with circulation in any large glacial fjord.

Page generated in 0.1111 seconds