Fluctuations of the Fisht Glacier (West Caucasus) over 1909–2015

Abstract

We have generalized observation data on the Fisht Glacier – the most western glacier in the Caucasus located at Pshekha and Belaya rivers headwaters at elevation 2450–2750 m asl. Considering location of the Fisht Glacier we might refer it as one of the most sensitive to climate change glaciers in the Caucasus. We used following materi‑ als: sketch map (1909), aerial photos (1954), topographic map (1957), detailed map (1:5000, 1982), LIDAR survey data (2010) and finally UAV data (2015). In two latter cases the horizontal and vertical uncertainties were less than 1 m. We note considerable shrinkage of glacier area from 0.9±0.1 to 0.5±0.01 km2 in 1909–2015, retreat of gla‑ cier termini was assessed as 200±20 m (eastern snout) and 350±20 m (western snout). We consider that during 1982–2010 the glacier was close to equilibrium, but during 2010–2015 glacier surface elevation lowering up to 15–20 m was accompanied by abrupt decrease of glacier area at about 15%. According to the data from nearest weather stations (Guzeripl’ and Krasnaya Polyana) and snow surveys over Pshekha catchment rapid glacier down‑ wasting in 2010–2015 could be explained by significant decrease of October‑May (accumulation season) precipi‑ tation and snow thickness accompanied by increase June‑September (ablation season) of air temperature in com‑ parison to 1982–2010. During 2010–2015 mean ablation assessed through degree‑day factor (DDF) was about 800 mm w.e. more than during 1982–2010. Basing on geodetical data on glacier change in 1982–2010 and ablation values assessed using DDF (4600 mm w.e.) we have roughly estimated mean accumulation at the Fisht Glacier as 4500 mm w.e. In 2010–2015 mean accumulation was at least 600 mm w.e. lower than in 1982–2010. As a result gla‑ cier in 2010–2015 the Fisht Glacier lost at least 1500 mm w.e. more than in 1982–2010. Basing on obtained results we could adjust regional pattern of glacier response to climate change in the Caucasus. Rarely applied in Russia both LIDAR and UAV techniques are recognized as precise tools for mapping of glacier surface in high mountains.