A GIS tool for automatic calculation of glacier equilibrium-line altitudes

Abstract

A toolbox for the automated calculation of glacier equilibrium-line altitudes (ELAs) using the Accumulation Area Ratio, Area-Altitude Balance Ratio, Area-Altitude and Kurowski methods is presented. These are the most commonly-used methods of ELA calculation in palaeo-glacier reconstructions. The toolbox has been coded in Python and runs in ArcGIS requiring only the reconstructed surface of the palaeo-glacier (a DEM) as input. Through fast and automatic calculation this toolbox simplifies the process of ELA determination and can successfully work both for a single glacier and for large datasets of multiple glaciers

GlaRe, a GIS tool to reconstruct the 3D surface of palaeoglaciers

“…The glacier-surface estimated ELA for the reconstructed icefield, which is arguably the most important use for palaeoglacier reconstructions, is very close to that of the extant glacier (Table 2). In particular, and whichever ELA methods and ratios are adopted (Pellitero et al, 2015), the difference in ELA between the reconstruction and real glacier is on the order of a few metres. The model with no F factor underestimates the ELA by ~15 metres, but the F factor model almost perfectly matches the real glacier ELA, with the error generally near that resulting from the contour belt elevation interval (see Pellitero et al, 2015), which was set to 5 metres for all reconstructions.…”

“…In particular, and whichever ELA methods and ratios are adopted (Pellitero et al, 2015), the difference in ELA between the reconstruction and real glacier is on the order of a few metres. The model with no F factor underestimates the ELA by ~15 metres, but the F factor model almost perfectly matches the real glacier ELA, with the error generally near that resulting from the contour belt elevation interval (see Pellitero et al, 2015), which was set to 5 metres for all reconstructions. It must be stressed that the extant glacier limit was used as input, so in this case there was no error in the horizontal geometry of the glacier reconstruction, as would likely be the case for the reconstruction of a fully deglaciated plateau.…”

“…snow and ice melted equals snow and ice accumulated within one year). ELAs can be calculated on present-day glaciers by making surface mass balance measurements (measured or geodetic) and can also be determined for palaeoglaciers using various techniques, most of which require knowledge of some component of the glacier geometry (Pellitero et al, 2015). Once a palaeoglacier ELA has been established, either the temperature or precipitation relating to it can be determined, providing quantitative palaeoclimate information for that location (Hughes and Braithwaite, 2008).…”

Glacier variations in the European Alps at the end of the last glaciation

“…Reconstruction of the surface of the Lagrev glacier (Fig. 5) implementing an ArcGIS automated tool (Pellitero et al, 2015) indicates an ELA depression of 220 m in comparison to the LIA ELA. The Great Aletsch glacier built single-walled, long, continuous lateral moraines during the Egesen stadial.…”

“…2). Glacier reconstruction with an ArcGIS toolbox (Pellitero et al, 2015) based on the equilibrium profile model of Benn and Hulton (2010 During cold periods associated with the Lateglacial stadials, in regions of the Alps with suitable topoclimatological conditions, especially in areas where the cirque floor or rockwall niche was below the regional ELA (Zasadni, 2007), rock glaciers developed (Kerschner, 1978;Kellerer-Pirklbauer et al, 2012). Relict rock glaciers several hundred meters below the present lower limit of discontinuous permafrost likely formed during the closing phase of the Egesen stadial (Kerschner, 1978;Maisch, 1987).…”