Accelerated wastage of the Monte Perdido Glacier in the Spanish Pyrenees during recent stationary climatic conditions

Abstract

Abstract. This paper analyzes the evolution of the Monte Perdido Glacier, the third largest glacier of the Pyrenees, from 1981 to the present. We assessed the evolution of the glacier's surface area by use of aerial photographs from 1981, 1999, and 2006, and changes in ice volume by geodetic methods with digital elevation models (DEMs) generated from topographic maps (1981 and 1999), airborne LIDAR (2010) and terrestrial laser scanning (TLS, 2011, 2012, 2013, and 2014). We interpreted the changes in the glacier based on climate data from a nearby meteorological station. The results indicate an accelerated degradation of this glacier after 2000, with a rate of ice surface loss that was almost three-times greater from 2000 to 2006 than for earlier periods, and a doubling of the rate of ice volume loss from 1999 to 2010 (the ice depth decreased 8.98 ± 1.8 m, −0.72 ± 0.14 m w.e. yr−1) compared to 1981 to 1999 (the ice depth decreased 8.35 ± 2.12 m, −0.39 ± 0.1 m w.e. yr−1). This loss of glacial ice has continued from 2011 to 2014 (the ice depth decreased 2.1 ± 0.4 m, −0.64 ± 0.36 m w.e. yr−1). Local climatic changes during the study period cannot explain the acceleration in wastage rate of this glacier, because local precipitation and snow accumulation increased slightly, and local air temperature during the ablation period did not significantly increase. The accelerated degradation of this glacier in recent years can be explained by the lack of equilibrium between the glacier and the current climatic conditions. In particular, the average air temperature increased by at least 0.9 °C in this region since the end of the Little Ice Age (LIA) in the mid-1800s. Thus, this glacier shrinks dramatically during years with low accumulation or high air temperatures during the ablation season, but cannot recover during years with high accumulation or low air temperatures during the ablation season. The most recent TLS data support this interpretation. These data indicated that two consecutive markedly anomalous wet winters and cool summers (2012–13 and 2013–14) led to near zero mass balance conditions, with significant losses of ice in some areas. These anomalous periods could not counteract the dramatic shrinkage that occurred during the dry and warm period of 2011–2012.