Abstract
Glaciers and rock glaciers play an important role in the hydrology of the semi-arid Northern Chile. Several studies show that glaciers have strongly lost mass in response to climate change during the last decades. The response to rock glaciers in this region is, however, much less investigated. In this study we use a combination of historical aerial photography, stereo satellite imagery, airborne LiDAR, and the Shuttle Radar Topography Mission (SRTM) DEM to report glacier changes for the Tapado Glacier-Rock Glacier complex from the 1950s to 2020 and to report mass balances for the glacier component of the complex, Tapado Glacier. Furthermore, we examine high-resolution elevation changes and surface velocities between 2012 and 2020 for 40 rock glaciers in La Laguna catchment. Our results show how the glacier has lost 25.2 ± 4.6 % of its ice covered area between 1956 and 2020, while the mass balance of Tapado Glacier has become steadily more negative, from being approximately in balance between 1956 and 1978 (−0.04 ± 0.08 m w.e. a−1) to showing strong losses between 2015 and 2020 (−0.32 ± 0.08 m w.e. a−1). Climatological (re)-analyses reveal a general increase in air temperature, decrease in humidity, and variable precipitation since the 1980s in the region. In particular the severe droughts in the region starting in 2010 resulted in a particular negative mass balance of −0.54 ± 0.10 m w.e. a−1 between 2012 and 2015. The rock glaciers within La Laguna catchment show heterogenous changes with some sections of landforms exhibiting pronounced elevation changes and surface velocities exceeding that of Tapado Glacier. This could be indicative of high ice contents within the landforms and also highlights the importance of considering how landforms can transition from more glacial landforms to more periglacial features under permafrost conditions. As such, we believe high-resolution (sub-metre) elevation changes and surface velocities are a useful first step for identifying ice-rich landforms.
Highlights
The cryosphere is in a state of rapid change, with glaciers thinning and losing mass on a global scale (Zemp et al, 2019)
This study focuses in detail on Tapado Glacier-Rock Glacier complex, an assemblage 65 landform consisting of a clean ice glacier (0.93 km2), a debris-covered glacier (0.32 km2) and a rock glacier (0.85 km2)
We found that certain rock glaciers had sections that were flowing at rates in excess of 4 m a-1, considerably faster than the catchment average of 0.54 ± 0.03 m a-1, as well as the surface velocities observed on the Tapado complex and Las Tetas rock glacier which are at least partly glacial in origin
Summary
The cryosphere is in a state of rapid change, with glaciers thinning and losing mass on a global scale (Zemp et al, 2019). Some studies have recently highlighted that given permafrost conditions are present, as well as a sufficient supply of 45 material from the surrounding slopes, a debris-covered glacier can transition to a rock glacier (Jones et al, 2019a; Knight et al, 2019; Monnier and Kinnard, 2017). 60 Recent studies have quantified glacier losses over the entire Andes (Braun et al, 2019; Dussaillant et al, 2019) Such studies provide invaluable regional scale information on glacier mass changes, at a limited spatial resolution and temporal scale. Glaciers are sparsely distributed in the semi-arid Andes, and as such studying decadal changes in surface lowering and mass balance can provide insights into the regional climate Such analyses are hampered by a lack of in-situ glaciological data in the region. We compare our results with temperature, precipitation and shortwave radiation data to assess the driving forces of the observed change
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