Permafrost evidence near Snezhnika microglaier, Pirin Mountain, Bulgaria

Snezhnika microglacier in Golyam Kazan, Pirin, Bulgaria is considered as the southernmost microglacier in Europe. Its size has been monitored since 1994, but information about its thickness and underlying structure is sparse. In 2018, 2019 and 2020 we conducted geophysical measurements, using ground penetrating radar (GPR) and resistivity tomography (ERT) in order to estimate the thickness and internal structure of the ice body as well as the subsurface structure beneath and near it.

The mean thickness estimated from GPR profiles is about 4–6 m, but can reach up to 8 m in the southern part of the ice body. These results are partialy in agreement with the results from early borehole measurements. ERT measurements in the lowest part of the microglacier’s bed show an anomaly with very high resistivity (> 60000 Ωm). The ERT measurements were repeated over 3 consecutive years, and the anomaly was detected during every measurement campaign. The values observed are typical for ice. This can be taken as evidence of permafrost in the Pirin Mountains. Our study provides more information on less investigated distribution of permafrost in low latitude areas, as well as on thickness of microglacier. This data for the thickness of the microglacier can be used for further studies on mass balance monitoring.