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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.
1

Trends in mass balance indexes connected to spatial location and precipitation : Remote sensing of 111 glaciers in the Everest region

Burström, Annika January 2012 (has links)
Studies of Himalayan glacial response to climatic forcing are few and a more comprehensive understanding of the relationship between the two is needed. This has been highlighted by recent controversies over future glacier change in this area. This study has therefore reviewed if there is a connection between glacier mass balance indexes and precipitation pattern in the Everest region. 111 glaciers were mapped in ArcGIS through remote sensing. Glacial total area, accumulation area as well as snowline altitudes and aspect were mapped. From this, the two mass balance indexes Accumulation Area Ratio, AAR and Area-Altitude Balance Ratios, AABR were derived. The intention was to search for patterns. In addition to this, an expedition to parts of the study area was conducted in March to April 2011. Hundreds of photographs of snow stratigraphy, debris cover ice snouts, accumulation etc were taken. The expedition also led to an understanding of the environment and of the glaciers which was helpful for the assessment of the remote sensing results. No pattern in glacier size, ELA, AAR or AABR was found that suggests a connection between mass balance and local precipitation pattern. The glaciers instead appear to be more sensitive to elevation. The largest glaciers and highest AAR and AABR are found at high - although not the highest - elevations.
2

Climatology and firn processes in the lower accumulation area of the Greenland ice sheet

Charalampidis, Charalampos January 2016 (has links)
The Greenland ice sheet is the largest Northern Hemisphere store of fresh water, and it is responding rapidly to the warming climate. In situ observations document the changing ice sheet properties in the lower accumulation area, Southwest Greenland. Firn densities from 1840 meters above sea level retrieved in May 2012 revealed the existence of a 5.5-meter-thick, near-surface ice layer in response to the recent increased melt and refreezing in firn. As a consequence, vertical meltwater percolation in the extreme summer 2012 was inefficient, resulting in surface runoff. Meltwater percolated and refroze at six meters depth only after the end of the melt season. This prolonged autumn refreezing under the newly accumulated snowpack resulted in unprecedented firn warming with temperature at ten meters depth increased by more than four degrees Celsius. Simulations confirm that meltwater reached nine meters depth at most. The refrozen meltwater was estimated at 0.23 meters water equivalent, amounting to 25 % of the total 2012 ablation. A surface energy balance model was used to evaluate the seasonal and interannual variability of all surface energy fluxes at that elevation in the years 2009 to 2013. Due to the meltwater presence at the surface in 2012, the summer-averaged albedo was significantly reduced (0.71 in 2012; typically 0.78). A sensitivity analysis revealed that 71 % of the subsequent additional solar radiation in 2012 was used for melt, corresponding to 36 % of the total 2012 surface lowering. This interplay between melt and firn properties highlights that the lower accumulation area of the Greenland ice sheet will be responding rapidly in a warming climate. / Stability and Variations of Arctic Land Ice (SVALI) / Programme for Monitoring of the Greenland Ice Sheet (PROMICE) / Greenland Analogue Project (GAP)

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