The Evolution of the Two Largest Tropical Ice Masses since the 1980s

Abstract

As tropical glaciers continue to retreat, we need accurate knowledge about where they are located, how large they are, and their retreat rates. Remote sensing data are invaluable for tracking these hard-to-reach glaciers. However, remotely identifying tropical glaciers is prone to misclassification errors due to ephemeral snow cover. We reevaluate the size and retreat rates of the two largest tropical ice masses, the Quelccaya Ice Cap (Peru) and Nevado Coropuna (Peru), using remote sensing data from the Landsat missions. To quantify their glacial extents more accurately, we expand the time window for our analysis beyond the dry season (austral winter), processing in total 529 Landsat scenes. We find that Landsat scenes from October, November, and December, which are after the dry season, better capture the glacial extent since ephemeral snow cover is minimized. We compare our findings to past studies of tropical glaciers, which have mainly analyzed scenes from the dry season. Our reevaluation finds that both tropical ice masses are smaller but retreating less rapidly than commonly reported. These findings have implications for these ice masses as sustained water resources for downstream communities.