Geodetic mass balance of Mýrdalsjökull ice cap, 1999−2021: DEM processing and climate analysis ; Bilan de masse géodésique de la calotte glaciaire Mýrdalsjökull, 1999−2021 : traitement de MNT and analyse climatique

Mýrdalsjökull is the fourth largest Icelandic ice cap (∼480 km² in 2019), located in the South of Iceland. Until now, the majority of mass balance studies in Iceland have been centered on the three main Icelandic ice caps. Thus, mass balance estimates of Mýrdalsjökull are scarce. The untapped SPOT5 archive (2002−2015), the lidar data, the Pléiades imagery (2011−present), aerial photographs from 1999 and the ArcticDEM dataset (2010−2019) were used in this study to create Digital Elevation Models (DEMs) of Mýrdalsjökull ice cap. A pre-processing of the DEMs was first performed: co-registration, filtering and interpolation. Then, applying a Gaussian Process regression (GP), a state-of-the-art method in DEM processing, a spatially and temporally continuous DEM dataset was created, in 15 x 15 m resolution and 30-day interval from 1999 to 2021. Volume and mass changes based on the synthetic GP-generated DEMs were computed and analyzed in 5-year intervals between 1999 and 2019. A mass loss of −1.23 ± 0.10 m w.e. a−1 was observed during this time span. Mass balance showed an increasing trend from −1.82 ± 0.16 m w.e. a−1 (1999−2004) to −0.39 ± 0.03 m w.e. a−1 (2014−2019). Glaciological mass balance computed annually showed less negative mass balance around 2014−2017, followed by another strong decline after 2017. A local analysis of three glacierized catchments of Mýrdalsjökull was performed. The northern catchment presented the most negative mass balance (−1.56 ± 0.16 m w.e. a−1 (1999−2019)). No significant variability in mass balance was observed between the catchments, despite noticeable differences in their climatic conditions. The relationship between glacier mass balance and climatic variations was investigated using a simplified linear model of mass balance forced by climate. A mass balance sensitivity to summer temperature of −1.35 m w.e. a−1 K−1 was obtained for Mýrdalsjökull, in agreement with the high mass balance sensitivity to temperature changes characteristic of maritime glaciers. ; Mýrdalsjökull, située ...