Figure 2
From: Projections of the future disappearance of the Quelccaya Ice Cap in the Central Andes
Snowline altitude using LANDSAT images. (a) Snow region in light blue, as a RGB composite using LANDSAT 5 (LT5) images of bands 5, 4, and 2, having applied histogram threshold values of 155 and 174 for bands 4 and 2, respectively. Snow line (SL) perimeter is shown in yellow and the black shading indicates the spatial domain of QIC, on 15 Sept. 1998. The mean SLA is calculated as the average elevation of all DEM cells coinciding with the location of the snow line perimeter. (b) As in (a), but for the date selected in 2016, and bands 6, 5 and 3 from LANDSAT 8 (LC8), with histogram threshold values of 99 and 117 for bands 5 and 3, respectively. (c) Mean SLA obtained each year (i.e. mean elevation corresponding to yellow perimeter). The dashed line represents the linear trend with equation indicated in the legend. The non-zero trend was verified using an F-test (p-value < 0.001), both with and without outliers (strong El Niño years 1998, 2010, 2016) included. Whiskers are representing the SLA error associated with the SLA standard deviation, LANDSAT spatial resolution, DEM vertical accuracy and slope in the SL perimeter.
