Abstract
Abstract. Measuring the ice flow motion accurately is essential to better understand the time evolution of glaciers and ice sheets and therefore to better anticipate the future consequence of climate change in terms of sea level rise. Although there are a variety of remote sensing methods to fill this task, in situ measurements are always needed for validation or to capture high-temporal-resolution movements. Yet glaciers are in general hostile environments where the installation of instruments might be tedious and risky when not impossible. Here we report the first-ever in situ measurements of ice flow motion using a remotely controlled unmanned aerial vehicle (UAV). We used a quadcopter UAV to land on a highly crevassed area of Eqip Sermia Glacier, West Greenland, to measure the displacement of the glacial surface with the aid of an onboard differential GNSS receiver. We measured approximately 70 cm of displacement over 4.36 h without setting foot onto the glacier – a result validated by applying UAV photogrammetry and template matching techniques. Our study demonstrates that UAVs are promising instruments for in situ monitoring and have great potential for capturing continuous ice flow variations in inaccessible glaciers – a task that remote sensing techniques can hardly achieve.
Highlights
Glacial motion is a key process governing the advance or the retreat of glaciers
A suitable site to land the quadcopter unmanned aerial vehicle (UAV) and to measure the ice motion must fulfill the following requirements: (i) be sufficiently flat to prevent the UAV from turning over and (ii) be in the line of sight of the operator and less than 2 km away to ensure a reliable connection with the remote controller, telemetry, and first-person view (FPV) (Fig. 4)
We identified our landing site on the middle flow line of Eqip Sermia Glacier and at 1.5 km of the closest glacier margin from the detailed digital elevation models (DEMs) inferred from the 11 July surveying flight (Fig. 1e)
Summary
Glacial motion is a key process governing the advance or the retreat of glaciers. The accurate recording of ice flow is crucial to calibrate models that can predict the future evolution of glaciers (e.g., Aschwanden et al, 2016). To continuously capture the dynamics of marine-terminating glaciers, it is necessary to develop methods that can measure their ice flow in high spatial and temporal resolution. In situ accurate GPS (e.g., Sugiyama et al, 2015; Murray et al, 2015) remains necessary (i) for validation purposes, (ii) to perform continuous measurements of ice movements and capture short timescale variability, (iii) to capture glacier vertical motion such as the tidal flexure of ice shelves (Le Meur et al, 2014), or (iv) to capture data whenever the weather prevents the use of remote sensing methods. Remote landings on ice without direct visual control have never been attempted before, especially over a highly crevassed glacier In this proof-of-concept paper, we report the outcomes of the first-ever use of a UAV for in situ sensing of glacial motion.
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