Ground-based remote-sensing techniques for diagnosis of the current state and recent evolution of the Monte Perdido Glacier, Spanish Pyrenees

This work combines very detailed measurements from terrestrial laser scanner (TLS), ground-based interferometry radar (GB-SAR) and ground-penetrating radar (GPR) to diagnose current conditions and to analyse the recent evolution of the Monte Perdido Glacier in the Spanish Pyrenees from 2011 to 2017. Thus, this is currently one of the best monitored small glacier (<0.5 km(2)) worldwide. The evolution of the glacier surface was surveyed with a Us evidencing an important decline of 6.1 +/- 0.3 m on average, with ice losses mainly concentrated over 3 years (2012, 2015 and 2017). Ice loss is unevenly distributed throughout the study period, with 10-15 m thinning in some areas while unchanged areas in others. GB-SAR revealed that areas with higher ice losses are those that are currently with no or very low ice motion. In contrast, sectors located beneath the areas with less ice loss are those that still exhibit noticeable ice movement (average 2-4.5 cm d(-1) in summer, and annual movement of 9.98 ma(-1) from ablation stakes data). GPR informed that ice thickness was generally <30 m, though locally 30-50 m. Glacier thinning is still accelerating and will lead to extinction of the glacier over the next 50 years.