Abstract
Abstract. Landslides in glacial environments are high-magnitude, long-runout events, believed to be increasing in frequency as a paraglacial response to ice retreat and thinning and, arguably, due to warming temperatures and degrading permafrost above current glaciers. However, our ability to test these assumptions by quantifying the temporal sequencing of debris inputs over large spatial and temporal extents is limited in areas with glacier ice. Discrete landslide debris inputs, particularly in accumulation areas, are rapidly “lost”, being reworked by motion and icefalls and/or covered by snowfall. Although large landslides can be detected and located using their seismic signature, smaller (M≤5.0) landslides frequently go undetected because their seismic signature is less than the noise floor, particularly supraglacially deposited landslides, which feature a “quiet” runout over snow. Here, we present GERALDINE (Google Earth Engine supRaglAciaL Debris INput dEtector): a new free-to-use tool leveraging Landsat 4–8 satellite imagery and Google Earth Engine. GERALDINE outputs maps of new supraglacial debris additions within user-defined areas and time ranges, providing a user with a reference map, from which large debris inputs such as supraglacial landslides (>0.05 km2) can be rapidly identified. We validate the effectiveness of GERALDINE outputs using published supraglacial rock avalanche inventories, and then demonstrate its potential by identifying two previously unknown, large (>2 km2) landslide-derived supraglacial debris inputs onto glaciers in the Hayes Range, Alaska, one of which was not detected seismically. GERALDINE is a first step towards a complete global magnitude–frequency of landslide inputs onto glaciers over the 38 years of Landsat Thematic Mapper imagery.
Highlights
There are currently >200 000 glaciers worldwide, covering >700 000 km2, of which 8.2 % are less than 1 km2 (Herreid and Pellicciotti, 2020), excluding the Greenland and Antarctic ice sheets (RGI Consortium, 2017)
Smith et al.: GERALDINE (Google Earth Engine supRaglAciaL Debris INput dEtector) ing characterized by expanding debris cover extents (Kirkbride and Deline, 2013; Scherler et al, 2011b; Tielidze et al, 2020)
Such deposits are commonly associated with rock avalanches (RAs), which are defined as landslides (a) of high magnitude (>106 m3), (b) perceived low frequency, (c) long runout, and (d) where there is disparity between high present-day rates of slope processes above ice (Allen et al, 2011; Coe et al, 2018) and expected rates based on theories of lagged paraglacial slope responses (Ballantyne, 2002; Ballantyne et al, 2014a)
Summary
There are currently >200 000 glaciers worldwide, covering >700 000 km, of which 8.2 % are less than 1 km (Herreid and Pellicciotti, 2020), excluding the Greenland and Antarctic ice sheets (RGI Consortium, 2017). Extensive debris coverage can alter the hydrological regime of a glacier (Fyffe et al, 2019), with the potential to increase or decrease downstream freshwater availability (Akhtar et al, 2008), and can play a key role in controlling rates of glacier thinning and/or recession, subsequently contributing to sea level rise (Berthier et al, 2010). This supraglacial debris control is thought to be important in the context of negative glacier mass balance, with retreating glaciers be-. Such deposits are commonly associated with RAs, which are defined as landslides (a) of high magnitude (>106 m3), (b) perceived low frequency, (c) long runout, and (d) where there is disparity between high present-day rates of slope processes above ice (Allen et al, 2011; Coe et al, 2018) and expected rates based on theories of lagged paraglacial slope responses (Ballantyne, 2002; Ballantyne et al, 2014a)
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