Glaciological investigations in east greenland using digital landsat imagery
University of Cambridge
Scott Polar Research Institute
Master of Philosophy (MPhil)
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Nuttall, A. (1993). Glaciological investigations in east greenland using digital landsat imagery (Masters thesis). https://doi.org/10.17863/CAM.12847
Sixteen late summer Landsat MSS scenes of East Greenland from 1986 to 1989 were acquired for use in glaciological and marine geological investigations. Drainage basin areas and snowline elevations were determined for 74 tidewater glaciers in the study area, and turbid meltwater plumes were identified. A method of correcting digital Landsat MSS data for the effects of atmospheric haze has been developed and tested. The method consists of subtracting the radiance value of clear, open water measured in each of the four bands from the total radiance of each band. Verification of the haze correction technique, by comparing two overlapping scenes acquired two days apart, showed that the results were consistent to within 6% or less in all bands over four terrain types: bare ice, snow, bare rock and turbid lakewater. Analysis of band 4 Landsat MSS data (0.8 to 1.1 ?m) has been used to identify ice divides and drainage basin areas for tidewater glaciers in East Greenland between 67°N and 75°N. Basin areas ranged from approximately 50,000 km2 for Daugaard-Jensen Gletscher and Kangerdlugssuaq Gletscher, both fast-flowing outlet glaciers draining tlie Greenland Ice Sheet, to about 20 km2 for small local glaciers. The largest basins lie mostly outside the study area, and estimates of their area were obtained from published elevation maps, where available. Smaller glaciers could not be resolved because of problems with delineating their boundaries due to shadowing, new snow and surface moraine. The ratio of basin area to terminus width of a glacier was shown to give an indication of dynamic regime, as a glacier with a large drainage basin, but only a narrow terminus is likely to be fast flowing, and vice versa. The late-summer snowlines were located for glaciers within the study area using MSS band 3 reflectance data (0.7 to 0.8 ?m) , and the elevations of these snowlines were determined from the published 1 :250,000 topographic maps. A trend was seen in the snowline elevations increasing northwards from about 200 m for glaciers south of Kangerdlugssuaq Fjord (68°N) to over 1000 mat the head of Kejser Franz Josef Fjord (74°N). The reliability of these estimates was investigated by using overlapping imagery where possible, and it was seen that much of the variability in the values could be explained if the snowline was still rising on the earlier images, or if new snow had fallen shortly before acquisition of the later images~ Meteorological data and a time series of imagery would be needed to confirm this hypothesis. Areas of higher reflectance in the vicinity of tidewater termini and river mouths were identified using MSS band 1 data (0.5 to 0.6 ?m). These are interpreted to be turbid meltwater plumes, and this conclusion is supported by comparison with photographs from the field. Meltwater plumes are an important mechanism for transporting suspended sediments to the marine environment, and their presence implies that at least part of the glacier bed is at the pressure melting point or above, and thus gives an indication of the thermal regime of the glacier. Sediments deposited in the fjords and on the adjacent shelves form a record of the palaeoclimate of the polar North Atlantic and the fluctuations of the Greenland Ice Sheet. Information useful for the interpretation of sediment cores could therefore be obtained by studying the distribution of meltwater plumes and their variation with latitude and drainage basin area.
This record's DOI: https://doi.org/10.17863/CAM.12847