We performed ground penetrating radar and global navigation satellite system surveys to investigate the ice thickness and flow of the Karamatsuzawa perennial snow patch, at the village of Hakuba, Nagano Prefecture. The field survey showed that the perennial snow patch contained an ice mass with a thickness greater than 30m and the ice flowed in the slope direction at a rate of 250mm over a 29-day period in the late snow-melting season in 2018. Based on the observed ice thickness and motion, the Karamatsuzawa perennial snow patch was recognised as an active glacier. The observed ice motion was significantly greater than the internal ice deformation estimated using Glenʼs Flow Law. This implies that basal sliding contributes to the motion of the Karamatsuzawa perennial snow patch.
