Abstract
ABSTRACTWe present a 1:42,000 scale map of Isunguata Sermia, a land-terminating outlet glacier draining the western-sector of the Greenland Ice Sheet. Structure-from-Motion software applied to ∼3,600 aerial images collected by a fixed-wing unmanned aerial vehicle in July 2015 allowed us to produce a high resolution (0.3 m ground sampling distance (GSD)) orthomosaic and digital elevation model (DEM; 1.5 m GSD).These products were used to map and describe the structural, geomorphological and hydrological features of the lower 16 km terminus of Isunguata Sermia and include many thousands of crevasses, crevasse traces and supraglacial channels. Additionally, several geomorphological features and pro-glacial hydrological features were identified, including debris-covered ice, lateral moraines and ice-marginal lakes. The map has potential for informing and reconstructing the long-term dynamic history of the glacier, including its response to variable environmental forcing.
Highlights
The structures found on glaciers, ice sheets and ice shelves provide information regarding past and present patterns of ice flow, as well as insights into the associated mechanical processes and properties of ice (Benn & Evans, 2010; Hulbe, LeDoux, & Cruikshank, 2010)
The lateral moraines mapped have a width of 80–100 m and are constrained by the glacier and valley walls. Both the velocity flow field and unmanned aerial vehicle (UAV)-derived digital elevation model (DEM) were used to distinguish between debris-covered ice and moraine features, with areas of debris-covered ice having a minimum velocity of 0.05 m d−1, whereas areas deemed to be moraine exhibited no signs of movement
We produced a 0.5 m resolution orthomosiac and 1.5 m resolution DEM from the application of Structure-from-Motion (SfM) photogrammetry to 3637 images obtained from three fixed-wing UAV surveys of a custom-built Skywalker X8
Summary
The structures found on glaciers, ice sheets and ice shelves provide information regarding past and present patterns of ice flow, as well as insights into the associated mechanical processes and properties of ice (Benn & Evans, 2010; Hulbe, LeDoux, & Cruikshank, 2010). Brittle features include faulting and crevasses (Hambrey & Muller, 1978), whereas ductile features include healed crevasse traces and foliation (Hambrey & Lawson, 2000) Both primary and secondary structures develop and evolve down-glacier as an expression of their cumulative strain history, and are commonly observed across the ice surface as relict or inherited features. In July 2015, over 245 km of UAV surveying was acquired over the terminus of IGS, yielding 4924 geo-tagged aerial images with a ground resolution equivalent to 30 cm These images were used to generate a georeferenced orthomosaic and digital elevation model (DEM) with an absolute horizontal and vertical accuracy of 5 and 8 m, respectively for both the orthomosiac and the DEM.
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