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  • 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.
41

Identifying Iceberg Production Processes, Drift Patterns, and Coexistence with Ships in the Eastern Canadian Arctic

Dalton, Abigail 30 August 2023 (has links)
Tidewater glaciers drain a significant proportion of the Greenland Ice Sheet and ice masses of the Canadian Arctic and provide the primary source of icebergs in Canadian waters. However, there remains uncertainty surrounding the processes controlling ice discharge from Canadian Arctic glaciers, the drift paths of icebergs in Canadian waters, and the proximity of icebergs to shipping in the region. This thesis quantifies the processes controlling glacier dynamics from four primary glacier basins on the Prince of Wales (POW) Icefield and using a multi-year dataset of iceberg drift tracks, identifies drift patterns and proximity to ships throughout the eastern Canadian Arctic. On the POW Icefield between 2009 and 2019, Cadogan and Ekblaw glaciers underwent multiyear acceleration and deceleration limited to their lower parts, consistent with characteristics of "pulse-type" glaciers. Trinity and Wykeham glaciers underwent repeating multiyear periods of velocity acceleration between 2009 and 2019 which coincided with significant thinning at their termini. As of 2017, Trinity and Wykeham were each within ~10 m of flotation over their lowermost 4 km. These findings suggest that Trinity and Wykeham glaciers have transitioned to a flow type dominated by dynamic thinning, which is strongly influenced by subglacial topography and may be susceptible to instability of the glacier front and large-scale collapse. Given that both glaciers are grounded below sea level for ~40 km up-glacier from their termini, this process could lead to significant increases in acceleration, retreat, and solid ice discharge. Using a multi-year dataset (2011-2019) of in-situ iceberg drift locations, it was found that icebergs consistently drifted southeast along the east coast of Baffin Island, controlled by a combination of local conditions including short-term wind events, ocean surface currents and semi-diurnal tidal oscillations. A test of the assumption that icebergs drift at 2% of the wind speed indicates that this rule does not apply for the majority of icebergs in this study, which typically exceeded 2% of the wind speed, particularly at low values. The highest median iceberg drift speeds occurred during the winter and spring, reaching up to 2.3 m s⁻¹ in Nares Strait. Icebergs in this study commonly became grounded near eastern Coburg Island and along the SE coast of Baffin Island, where mean residence time exceeded 180 days in all seasons. Through an analysis of a comprehensive database of ship tracks derived from AIS (automatic identification system) data in combination with a subset of iceberg drift locations derived from in-situ satellite trackers and the Canadian Ice Island Drift, Deterioration, and Detection Database (CI2D3), areas of iceberg-ship coexistence throughout Baffin Bay were identified between 2012 and 2019. The regions that saw the largest increases in iceberg-ship coexistence were along the east coast of Baffin Island and east of Bylot Island for dry bulk vessels, and northward into Smith Sound for passenger vessels. As passenger vessels commonly have little ice strengthening, this could pose an elevated hazard to vessels operating in these regions. The results of this study provide a comprehensive examination of the factors controlling glacier terminus dynamics and stability on SE Ellesmere Island, and the drift paths of icebergs once calved. This provides insights into the life cycle of icebergs in Canadian waters, how they may change in a warming climate, and the hazards that they may pose for shipping, particularly given the rapid recent increase in ship transits across the Canadian Arctic.
42

Glacial Geology of Northcentral Hancock County, Ohio

Bugh, James E. January 1962 (has links)
No description available.
43

Glacial Geology of the Northeastern Portion of Hancock County, Ohio

Swanston, Douglas N. January 1962 (has links)
No description available.
44

An assessment of the ice masses of Axel Heiberg Island, N.W.T. : a study of glacier inventory

Ommanney, C. Simon L., 1942- January 1968 (has links)
Note:
45

Spatial and temporal dynamics of three East Antarctic outlet glaciers and their floating ice tongues

Wuite, Jan 16 November 2006 (has links)
No description available.
46

Seismic investigation of ice properties and bedrock topography at the confluence of two glaciers, Kaskawulsh Glacier, Yukon Territory, Canada /

Dewart, Gilbert January 1968 (has links)
No description available.
47

Ice ablation measured by stakes and by terrestrial photogrammetry : a comparison on the lower part of the White Glacier, Axel Heiberg Island, Canada

Arnold, Keith C. January 1978 (has links)
No description available.
48

Determination of changes of surface height, 1957-1967, of the Gilman Glacier, North Ellesmere Island, Canada.

Arnold, Keith C. January 1968 (has links)
No description available.
49

Rock Glaciers of the Contiguous United States: Spatial Distribution, Cryospheric Context, and Riparian Vegetation

Johnson, Gunnar Forrest 02 August 2018 (has links)
Continental-scale inventories of glaciers are available, but no analogous rock glacier inventories exist. We present the Portland State University Rock Glacier Inventory (n = 10,343) for the contiguous United States, then compare it to an existing inventory of contiguous United States glaciers (n = 853), identifying geographic and climatic factors affecting the spatial distributions observed. At least one rock glacier is identified in each of the 11 westernmost states, but nearly 90% are found in just five; Colorado (n = 3889), Idaho (n = 1723), Montana (n = 1780), Utah (n = 834), and Wyoming (n = 849). Glaciers are concentrated in relatively humid mountain ranges, while rock glaciers are concentrated in relatively arid mountain ranges. Mean glacier area (0.60 ± 0.073 km2) is significantly greater than mean rock glacier area (0.10 ± 0.002 km2), though total glacier area (507.70 km2) is lower than total rock glacier area (1008.91 km2). Glacier and rock glacier areas, as a percent of small watersheds containing them, are modeled using geographically weighted regression. Glacier percent area (R2 = 0.55) is best explained by elevation range and mean fall snowfall, while rock glacier percent area (R2 = 0.42) is best explained by mean spring dewpoint temperature and slope standard deviation. Finally, we compare riparian vegetation along meltwater streams draining glaciers and rock glaciers. Initial 500 m long meltwater stream reaches emanating from a total of 35 pairs of collocated glaciers and rock glaciers were delineated, allowing estimation of riparian vegetation cover and density. Rock glacier meltwater stream riparian vegetation cover (mean cover = 86.2% ± 9.3%) and density (mean NDVI = 0.30 ± 0.02) are significantly greater (p-value < 0.05) than glacier meltwater stream riparian vegetation cover (mean cover = 64.5% ± 10.9%) and density (mean NDVI = 0.13 ± 0.01). This study shows that while the spatial distributions of glaciers and rock glaciers are both generally influenced by a combination of geographic and climatic variables, the specific forcings and local magnitudes are distinct for each cryospheric feature type, and processes inherent to rock glacier cryospheric meltwater sourcing positively influence first-order meltwater stream vegetation patterns.
50

Relative age dating of the Wahianoa moraines, Mount Ruapehu, New Zealand : thesis submitted in partial fulfilment of the degree of Master of Science in Quaternary Science at Massey University, Palmerston North, New Zealand

Nolan, Erin Unknown Date (has links)
This study attempts to determine a relative age of the Wahianoa moraines, Mt Ruapehu using three relative age dating techniques: Lichenometry, Schmidt hammer and Boulder roundness. There were three study areas used, termed the Wahianoa ‘A’, ‘B’ and ‘C’ moraines. Upon determining a relative age for these moraines, their timing of their formation was placed within New Zealand’s glacial timescale. This is the first study of its kind conducted on Mt Ruapehu and has left the door open for more research in this field. The species of lichens measured on the Wahianoa moraines were Rhizocarpon subgenus, which the largest diameters were measured using callipers. A total of 606 lichens were measured in the Wahianoa Valley and were processed using the growth curve and size frequency methods. A lichenometric growth curve was constructed from lichens growing in the Ohakune cemetery. The dates derived from both methods placed the formation of the Wahianoa moraines during the Little Ice Age. An L-type Schmidt hammer was used on the boulders in the Wahianoa Valley. A total of 280 measurements were taken off the boulders on the Wahianoa moraines. The results of this method, when compared to Winkler’s (2005) study in the South Island placed the formation of the Wahianoa moraines pre-Little Ice Age. Although no definitive ages could be derived from this comparison due to differences in lithology between the two studies, it provided an idea as to where the formation of these moraines could belong. This is the first time that the Boulder roundness method has been used in New Zealand, having only been developed by Kirkbride (2005). This method was used to determine which of the ridges in the Wahianoa Valley were older. It was found that the Wahianoa ‘A’ moraines were the oldest in the valley followed by Wahianoa ‘B’ and ‘C’ respectively. A climate reconstruction was also conducted for the Wahianoa Valley to see what conditions may have been in existence during the formation of the Wahianoa moraines. The paleo-ELA for the Wahianoa Glacier was estimated using the Accumulation-Area Ratio (AAR), Terminus to Headwall Ratio (THAR), Maximum Elevation of the Lateral Moraines (MELM) and Extrapolation methods. The current ELA was estimated using the AAR, THAR and Extrapolation methods. The difference between these estimates was used to determine what temperature decrease would have caused the formation of the Wahianoa moraines. The average paleo-ELA was found to be c. 1715m, while the current ELA was found to be 2475m which lead to a 4.5°C decrease. This temperature decrease correlates well with that of the Last Glacial Maximum. This study found significant differences in relative age of the Wahianoa moraines. There are a number of factors that can affect the growth of lichens such as micro-environmentalconditions and the fact that a growth curve was constructed off site. Factors such aspetrography can affect the Schmidt hammer results and the Boulder roundness measurements. In addition, precipitation can affect the ELA values which can then cause the wrong placement within a glacial event. Further research lies in the use of the Schmidt hammer on a known age surface such as the Mangatepopo moraines which will aide in a better correlation of relative age. Also, further research using climate reconstructions on Mt Ruapehu and the effect of precipitation will also aide in a better correlation with a glacial event.

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