Black Rapids Glacier mass balance, Eastern Alaska Range, 1972-2016

Black Rapids Glacier is a surge-type glacier in the Eastern Alaska Range. It has been monitored annually since 1972, when the United States Geological Survey initiated a mass balance program. After the program was discontinued by the agency it was picked up by the University of Alaska Fairbanks. Initially, up to 12 sites were measured for seasonal mass balance, but the program was scaled back to four sites in the ablation and lower accumulation area of the glacier and to annual balances only. The data series is one of the longest mass balance series in the world, and probably the longest on a surge-type glacier. It captures what appears to be the transition from a surge-type glacier to one that might no longer be able to build up to surge geometry due to continued warming.