Most of the alpine glaciers in the world are shrinking. Because of the impact glaciers have on watershed hydrology, the US Geological Survey began a surface mass balance measurement program on Sperry Glacier in Glacier National Park, Montana, USA, in 2005. Between then and 2015 the USGS employed standard methods to estimate the mass changes across the surface of the glacier. During this 11-year period, Sperry Glacier had a cumulative mean mass balance loss of 4.37 m of water equivalent.