Emerging Glacial Lakes in the Cordillera Blanca, Peru: A Case Study at Arteson Glacier

Tropical glaciers are an essential component of the water resources systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean glaciers in recent decades. The shrinkage of Andean glaciers influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some glaciers. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical glaciers in Peru and how climate change is likely to impact glacial melt and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to glaciers in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect glacier mass balance. This study presents GPR data taken in July 2012 at the Arteson glacier in the Cordillera Blanca, Peru. A new lake has begun to form at the terminus of the Arteson glacier, and this lake has key features, including overhanging ice and loose rock likely to create landslides, that could trigger a catastrophic GLOF if the lake continues to grow. This new lake is part of a series of three lakes that have formed below the Arteson glacier. The two lower lakes, Artesonraju and Paron, are much larger so that if there were an avalanche or landslide into the new lake below Arteson glacier, the impact could potentially be more catastrophic than a GLOF from one single lake. Estimates of how the lake mass balance is likely to evolve due to the retreating glacier are key to assessing the flood risk from this dynamic three-lake system. Because the glacier mass balance and lake mass balance are closely linked, the ice thickness measurements and measurements of the bed slope of the Arteson glacier and underlying bedrock give us a clue to how the lake is likely to evolve. GPR measurements of Arteson glacier show the ice thickness ranging from 20 meters at the terminus and gradually increasing to about 160 meters at the highest part of the glacier. A negative bed slope from the glacier terminus to the higher elevations of the glacier indicates that the conditions are favorable for the growth of a glacial lake, and this growth is likely to be limited only by the amount of ice available and the rate of melt. A more informed glacier melt model that accounts for the ice thickness and glacial extent can give us better estimates of the future mass balance of the new glacial lake at the base of the Arteson glacier. These mass balance estimates will in turn influence hydraulic models of potential GLOFs for the glacial lake system below Arteson glacier and the resulting risk assessment studies.