Rock glaciers (RGs) are permafrost landforms occurring in many alpine regions. Gravimetry measures g (acceleration due to gravity). Decreases in water and/or ice content in the ground near a measurement point make g decrease, too. In this first study of its kind, we measured changes in g to calculate subsurface ice melt in a RG. Our approach helps measure and understand invisible underground ice and water processes in rapidly changing permafrost environments.