TROPICAL ICE-CAP FOUND TO BE MELTING SLOWER, THE CASE OF NEVADO COROPUNA VOLCANIC COMPLEX SOUTHERN PERU

Coropuna in southern Peru (15° 33’ S, 72° 38’ W; 6,425 m) hosts the largest mass of ice in the tropics on any volcano (~45 km² in 2014). Thus, it presents a significant risk to surrounding inhabitants during future eruptions and it is also a critical freshwater resource to the region, which is dominated by agriculture and relies on snow and ice melt for year round water supplies. Estimates of ice retreat rates at Coropuna from previous workers have been used to suggest that the ice is melting rapidly. However, previous authors have used images from high snow months (i.e., June and July), leading to overestimates of ice area. We used Landsat scenes, a SPOT scene, and ground photos to digitally reconstruct the area evolution of glaciers on Coropuna, southern Peru. All satellite images are from November and December when snow is at an annual minimum. Glacierized areas were found to be 64, 58, 56, 53, 52, and 45 km² in 1975, 1980, 1987, 1996, 2003, and 2013 respectively. This represents shrinking at ~0.5 km²/yr, approximately one third of the rates previously published. In 1911, Yale Scholar, Hiram Bingham became the first European to ascend Coropuna during one of his Peruvian expeditions. During his climb of Coropuna he took photos of the ice. Assuming a linear rate of retreat since 1911, estimates from previous authors would give reconstructed ice areas of ~200 km² in 1911, while this study suggests that it was only ~90 km². Comparison of the photos from 1911 and 2015 show that while glacial shrinking is occurring, it is not as dramatic as previously inferred. This study suggests that ice will persist at least until 2100, assuming rates of ice loss do not increase significantly. The persistence of ice on Coropuna into the next century will be critical to local economies based on agriculture in several river drainages to the south and west of Coropuna.