Monitoring tropical debris-covered glacier dynamics from high-resolution unmanned aerial vehicle photogrammetry, Cordillera Blanca, Peru

Abstract

Abstract. The glaciers of the Cordillera Blanca, Peru, are rapidly retreating and thinning as a result of climate change, altering the timing, quantity and quality of water available to downstream users. Furthermore, increases in the number and size of proglacial lakes associated with these melting glaciers is increasing potential exposure to glacier lake outburst floods (GLOFs). Understanding how these glaciers are changing and their connection to proglacial lake systems is thus of critical importance. Most satellite data are too coarse for studying small mountain glaciers and are often affected by cloud cover, while traditional airborne photogrammetry and lidar are costly. Recent developments have made unmanned aerial vehicles (UAVs) a viable and potentially transformative method for studying glacier change at high spatial resolution, on demand and at relatively low cost.Using a custom designed hexacopter built for high-altitude (4000-6000 m a.s.l.) operation, we completed repeat aerial surveys (2014 and 2015) of the debris-covered Llaca Glacier tongue and proglacial lake system. High-resolution orthomosaics (5 cm) and digital elevation models (DEMs) (10 cm) were produced and their accuracy assessed. Analysis of these datasets reveals highly heterogeneous patterns of glacier change. The most rapid areas of ice loss were associated with exposed ice cliffs and meltwater ponds on the glacier surface. Considerable subsidence and low surface velocities were also measured on the sediments within the pro-glacial lake, indicating the presence of extensive regions of buried ice and continued connection to the glacier tongue. Only limited horizontal retreat of the glacier tongue was observed, indicating that measurements of changes in aerial extent alone are inadequate for monitoring changes in glacier ice quantity.

GLOFs in the WOS: bibliometrics, geographies and global trends of research on glacial lake outburst floods (Web of Science, 1979–2016)

“…Mergili et al, 2018;Westoby et al, 2014) despite rapid progress in this direction and improvements to technical capabilities as well as data availability and acquirability (e.g. Mallalieu et al, 2017;Wigmore and Mark, 2017). This study shows how research on GLOFs published in the Web of Science Core Collection database has become topical over the past few decades (analysed period 1979-2016), how the publishing culture and paradigm have changed over time and what the trends and disproportions in geographies of research on GLOFs are.…”

Mapping Surface Flow Velocity of Glaciers at Regional Scale Using a Multiple Sensors Approach

“…Hence, large scale, comprehensive and frequent (e.g., sub-seasonal) mappings of the glacier surface velocity would be needed to accurately estimate ice thickness, but also to understand the variability in glacier dynamics. Nowadays, these speed maps are spatially and temporally scarce and at coarse resolution, which has hampered our understanding of glacier evolution in mountain regions [11,12]. Specifically, the recent studies at regional scales using the growing archive of optical and radar data have focused on the largest glacier-covered regions [13][14][15][16] with a spatial resolution excluding a large proportion of glaciers that have an area smaller than 5 km 2 and limiting the application of the developed methodologies to regions containing smaller glaciers (e.g., the European Alps or the tropical Andes).…”

On the Use of Unmanned Aerial Systems for Environmental Monitoring

“…(v) Vulnerability of UAS to weather conditions (e.g., wind, rain) can alter quality of the surveys. (vi) There are also technical limits, such as weather constraints (strong wind and/or rain), high elevations, or high-temperature environments that can be challenging for most of the devices/sensors and respective UAS operators (see, e.g., [155]). (vii) The geometric and radiometric limitations of current lightweight sensors make the use of this technology challenging.…”