Recent evolution and present situation of the world’s largest tropical icefield: the Nevado Coropuna (Peru).

With around 46 km², Nevado Coropuna (NC, (15°32’S, 72°39’W; 6377 m) is the largest tropical icecap in the world. NC is situated on a stratovolcano structure with six peaks over 6000 meters, in the arid border of the Andean plateau, Southern Peru. NC is a vital source of freshwater for the communities within the Majes valley and for the vast irrigation plans located in the same valley and on the arid coastal strip. Here we present the 1955-2024 glacier surface evolution, which was retrieved from aerial photography and topographic maps for the initial stage in 1955 and from satellite imagery photogrammetry (SPOT, Worldview, PeruSAT-1 and Pleiades), backed by in-situ GPS-RTK measurements for the last 11 years.

Results show that the glacier lost an average of -0.15 m a^-1 of ice between 1955 and 2013. The ice loss subsequently accelerated to a rate of -0.18 m a^-1 between 2013 and 2018 and -0.44 m a^-1 between 2018 and 2023. During the last year the ice loss rate has been -0.15 m a^-1.

Ice loss has not been even across the glacier, but it primarily concentrated on the largest northern outlets, where it approached -1.9 m a^-1 between 2018 and 2024 with a much lower ice reduction (-0.9 m a^-1) in the southern outlets. Ice loss at the peaks is also reported, as a difference between a negligible ice change in the 1955-2013 timeframe contrasts a -0.7 m a^-1 ice loss at the central part of the NC top plateau during the 2018-2024 timespan. The extensive debris-covered and rock glacier area features a much more stable behaviour, with ice loss/gain values within the error limit between 2013 and 2024. Likewise, the northwestern section of NC seems quite stable, possibly because of its comparatively higher elevation.

Results in NC show a continuous and consistent glacier retreat, but the mass loss pace is less accelerated than other Peruvian glaciers. Glaciers in the Vilcanota range, in the humid margin of the Andes, show a -0.5 m a^-1 ice loss between 2000 and 2020 and there is an even stronger ice loss acceleration in the Central Andes area after 2013, with an average mass change of -1.067 m a^-1.