The use of snowline altitude of mountain glaciers as indicators of climate change in the tropical Andes from remote sensing data: a case study on Nevado Sajama, Bolivia

This paper describes the application of remote sensing for the estimation of the snowline equilibrium altitudes of mountain glaciers in the outer tropics and the use of snowline altitudes as a valuable approximation of the equilibrium line altitude of the year and hence to get the most proximal estimation of annual mass balance changes. In this case study, we used the images from Landsat series – MSS, TM, ETM+ and Landsat 8 - images of the Nevado Sajama in the Western Cordillera in Bolivia. Snowline altitude of a selected outlet glacier of the study site for each year during the dry season was calculated and the maximum snowline calculated during the dry season can be taken as the equilibrium line altitude of the year. Anomalies in precipitation and air temperature were calculated and compared with the observed differences in the calculated annual snowline changes. We also considered three ocean-atmospheric oscillations in the Pacific – ENSO, PDO and AAO. It is found that the snowline altitude of this mountain glacier have been fluctuated with the cold and warm regimes of ENSO and PDO. It is hypothesized that the retreat of this mountain glacier in the Western Cordillera is not as rapid as the Eastern Cordillera in the outer tropics, probably due to the cold regimes of PDO and high altitude of the Nevado Sajama retards the rapid ablation in this region.