Dynamics of the Greenland Ice Sheet and Icelandic Glaciers in the 20th Century Using Geodetic Methods
The main focus of this thesis is on geodetic methods of estimating mass change of the GrIS, mainly through photogrammetric processing of historical aerial photographs, which are used to produce a Greenland-wide digital elevation model for the years 1978-1987. Photogrammetric stereo-models are also u...
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| Format: | Book |
| Language: | English |
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Natural History Museum of Denmark, Faculty of Science, University of Copenhagen
2015
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| Online Access: | https://curis.ku.dk/portal/da/publications/dynamics-of-the-greenland-ice-sheet-and-icelandic-glaciers-in-the-20th-century-using-geodetic-methods(2f204754-b502-4ad8-91cb-1e108ee9cdf3).html https://soeg.kb.dk/permalink/45KBDK_KGL/1pioq0f/alma99122152819705763 |
| Summary: | The main focus of this thesis is on geodetic methods of estimating mass change of the GrIS, mainly through photogrammetric processing of historical aerial photographs, which are used to produce a Greenland-wide digital elevation model for the years 1978-1987. Photogrammetric stereo-models are also used to map the glacial imprint on the landscape in order to geometrically reconstruct the mass changes between the Little Ice Age (LIA) (~1900) to 1978-1987. Thus, the observational record is extended more than a decade (DEM), to around a century (geomorphological mapping). In order to provide a basis for analysis, these results are combined with modern laser altimetry, climate data, and a variety of other geophysical data. The results presented in this thesis, show that the margins respond rapidly and highly dynamic to external climatic forcing, followed by deceleration and stabilization controlled by bedrock geometry. It is revealed that dynamic ice loss recently seen in the southeast and northwest GrIS also occurred in the northwest between 1985 and 1993, highlighting the difficulty of capturing these events in mass balance models. Extending the record back to the LIA, the results show that for the past 110 years, the surface mass balance has been decreasing, while the dynamic term has been constant. The spatial pattern of thinning in the 20th century is identical to that of current change, suggesting this pattern will continue in the near future. The mass change of the GrIS in 20th century is converted into global mean sea level rise, adding closure to the 20th sea level budget. In order to quantify the impact of a fast-flowing glacier on the landscape, the location changes to Brúarjökull, Iceland. Brúarjökull is a dynamic surge-type glacier, and aerial photographs are available from before and after its 1963/1964 surge. Combined with field-surveyed geodetic control and a digital map of landforms, DEMs of Difference are produced and analysed on a landform and landsystems level. Large volumes of sediment was ... |
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