UAV-based investigations into the hydrology and dynamics of the Greenland Ice Sheet

• Main Author: Chudley, Thomas
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of Cambridge 2020
• Subjects: glaciology; ice sheet; Greenland Ice Sheet; Greenland; Uncrewed Aerial Vehicle; UAV; remote sensing; feature tracking; GNSS; GPS; photogrammetry; supraglacial hydrology; supraglacial lake drainage; crevasses; crevasse hydrology; ice dynamics; hydrofracture; Store Glacier; Sermeq Kujalleq; Kujalleq; glacier; Ice Sheet
• Online Access: https://www.repository.cam.ac.uk/handle/1810/311597; https://doi.org/10.17863/CAM.58689

Variation in the rate of meltwater input into the subglacial system of the Greenland Ice Sheet can force dynamic responses on a range of scales from hourly to interannual. Observations of the ice sheet dynamic response are commonly made either through ground-based Global Navigation Satellite System (GNSS) measurements, which can provide continuous and accurate point measurements, or through satellite remote sensing, which can provide regional-scale observations but at coarse temporal resolutions. This thesis investigates the potential of Uncrewed Aerial Vehicles (UAVs) to provide intermediate-level observations of the interactions between ice sheet hydrology and dynamics at a fast-flowing, marine terminating glacier in West Greenland. I first describe the development of a low- cost UAV suitable for deriving ice sheet velocity fields from Structure-from-Motion photogrammetry. In order to geolocate products without using ground control, image locations are determined directly using an on-board L1 GNSS receiver. I validate this method, showing that accuracies are sufficient for producing velocity fields in the ice sheet interior. Next, this method is used, alongside in-situ geophysical observations, to characterise the causes and dynamic influence of a rapid supraglacial lake drainage. I show that rapid drainage can induce a significant dynamic response up to 4 km away from the lake itself, and that fracture history can exert controls on interannual lake drainage behaviour. Finally, I upscale UAV ob- servations using satellite datasets over a ~3,000 km² area, exploring dynamic controls on crevasse hydrology. I find that in compressive mean stress compressive regimes, crevasses are more likely to display ponding and rapid hydrofracture than in extensional regimes, where continuous slow drainage is typical. Continued high-resolution observations are necessary to further identify key controls on the hydrological influences of Greenland Ice Sheet dynamics. Funded by a Natural Environment Research Council studentship ...