The Potential for Total Loss of the World's Largest Tropical Ice Mass (Quelccaya Ice Cap, Peru)

Tropical glaciers are rapidly retreating under Anthropogenic climate change, presenting challenges to communities that depend on them for water and tourism resources. The world's largest tropical ice mass (Quelccaya Ice Cap, Peru) is perched upon a broad plateau, which limits how far upslope it can retreat in response to current and future climate changes. This study identifies the amount of climate change that would commit the Quelccaya Ice Cap to total loss, using a 2-D shallow ice flow model. The near-term and long-term fate of the ice cap is forecasted using output from CMIP5 experiments for the various Representative Concentration Pathway (RCP) climate change scenarios.

Climate changes that push the equilibrium line altitude (ELA) to roughly the summit bedrock elevation commit the Quelccaya Ice Cap to total loss. The current ELA is uncertain, but estimates range from 5,300 to 5,000 m a.s.l., i.e., about 50 to 200 meters lower than the summit bedrock. For all climate change scenarios, the ELA is forecasted to be pushed above the complete deglaciation elevation during the 21^st century. Under the most aggressive mitigation scenario (RCP 2.6), however, complete deglaciation may be averted, given the ice cap's response time and 21^st and 22^nd century cooling due to aggressive climate change policies. Under the other three climate change scenarios, total loss of the Quelccaya Ice Cap appears to be assured by the end of the 21^st century (RCP 8.5 - business as usual) or the early/middle 22^nd century.

This study identifies climate changes that would commit the world's largest tropical ice mass to total loss and provides forecasts for its fate in an Anthropogenic world. The findings also highlight the urgency for actions to lessen and undue Anthropogenic climate change to ensure the existence of Earth System components that are vital for communities.