**6. Discussion: small glaciers on the Balkans and climate variations**

To understand the nature of short-term glacier variations, we have to bear in mind the climate of the mountains which contain these glaciers. All the three discussed areas are in the zone of transition between the temperate and subtropical (Mediterranean) climate. Located close to the Mediterranean sea (70–100 km away), they are not standing right on the coast, and being among the highest ranges, they are open to continental influences from mainland Europe [3, 12, 33, 42, 43]. Climatic data for these high mountain areas are also lacking. For reference, for a longer period in Pirin, the climatic station of Musala peak in Rila (2925 m a. s. l., 54–55 km away from the glacierets) is used [44]. In the last years measuring devices have been installed in the target area of Pirin such as in Golemia Kazan, close to Snezhnika, by K. Grunewald (an automatic meteorological station recording since September 2011) and on the top of Vihren peak by the South-west University of Bulgaria (logger-sensors, recording every 30 minutes air temperature and humidity since October 2014; and ground temperature since 2016). The statistically significant correlation of temperature data between Musala peak and Golemia Kazan cirque shows that the information from Musala (available also in Internet at [44]) can be used to estimate conditions in Northern Pirin [45]. However, for the last 5 years data from the station near Snezhnika have shown quite high air temperature (annual around +2°C [46]). Analysis of data from Musala enabled to calculate temperature monthly and annual averages for 1994–2016 (**Figure 12**).

**6. Discussion: small glaciers on the Balkans and climate variations**

**Figure 11.** Area measurements for Snezhnika glacieret (Pirin) and Debeli namet glacier (Durmitor).

1994–2016 (**Figure 12**).

96 Glacier Evolution in a Changing World

To understand the nature of short-term glacier variations, we have to bear in mind the climate of the mountains which contain these glaciers. All the three discussed areas are in the zone of transition between the temperate and subtropical (Mediterranean) climate. Located close to the Mediterranean sea (70–100 km away), they are not standing right on the coast, and being among the highest ranges, they are open to continental influences from mainland Europe [3, 12, 33, 42, 43]. Climatic data for these high mountain areas are also lacking. For reference, for a longer period in Pirin, the climatic station of Musala peak in Rila (2925 m a. s. l., 54–55 km away from the glacierets) is used [44]. In the last years measuring devices have been installed in the target area of Pirin such as in Golemia Kazan, close to Snezhnika, by K. Grunewald (an automatic meteorological station recording since September 2011) and on the top of Vihren peak by the South-west University of Bulgaria (logger-sensors, recording every 30 minutes air temperature and humidity since October 2014; and ground temperature since 2016). The statistically significant correlation of temperature data between Musala peak and Golemia Kazan cirque shows that the information from Musala (available also in Internet at [44]) can be used to estimate conditions in Northern Pirin [45]. However, for the last 5 years data from the station near Snezhnika have shown quite high air temperature (annual around +2°C [46]). Analysis of data from Musala enabled to calculate temperature monthly and annual averages for

**Figure 12.** Climatic averages for the area of Snezhnika glacieret based on data from Musala peak: (a) monthly averages for the period 1994–2016; (b) averaged data for 1994/1995—2015/2016 balance years.

What is clear from the figure is that according to the data, there has been registered a considerable warming trend for last 23 years in annual, ablation and summer temperatures. Analyses showed that there is a relatively good correlation between thermal variables, calculated in balance years, and the area of Snezhnika glacieret. For the 23 year period the best is the correlation with the sums of positive temperatures (ablation season sums) which is −0.73.

Why is then no trend in the development of Snezhnika glacieret, if the temperature rise is a fact? The answer is sought in the influence of precipitation, but data about this climatic element are almost missing in Pirin. However, analysis of precipitation data from Musala (with lots of uncertainties) shows that the stagnation of Snezhnika can be due to the higher sums of winter precipitation, which have been registered in most of the years after 2004.

As the annual precipitation in the high parts of Pirin is suggested to be around 1000–1100 mm/ year, 650–700 mm of which during the accumulation season [26, 42], Snezhnika is fed to a greatest extent by avalanche and windblown snow. Thus, it receives snow amounts much larger than the actual sum of atmospheric precipitation. On the contrary, Banski suhodol has much smaller avalanche catchment [8]. It relies most of all on shading, and its variations through years are smaller than those of Snezhnika [3]. Sadly, precipitation data from the devices installed in Pirin are not reliable [45, 47].

No climatic data are available from the high mountain areas of Prokletije and Durmitor, the closest mountain station being on Bjelašnica peak in Bosnia and Herzegovina (2067 m a. s. l.). Extrapolations of temperature for the last decade however suggest that around 2150 m a. s. l., annual temperatures are around +2°C and more, and even near the highest glaciers, they are positive [12, 14, 18]. These are however temperatures for open slopes. In negative forms, values are by no doubt lower but still high to sustain glaciers. In the Western Balkans, the existence of perennial ice is favoured by the much greater precipitation: annual amounts for the highest areas of Durmitor are about 2600 mm [18, 33], and for the central and western parts of Prokletije 2500–3300 mm, 2/3 of this amount falling in the cold half of the year [12, 43, 48]. This enables formation of glaciers even at altitudes around 2000 m in strongly shaded sites. The plateau surfaces in the south of Debeli namet and Kolata glaciers serve as great sources of snow, so the actual amount of snow can be more than twice the winter precipitation sum. Glaciers around Mt. Jezerce rely most of all on high altitude (comparable to that of Snezhnika in Pirin) and precipitation around 2500 mm/year and those in Karanfili range mainly on strong shading. Glaciers in Hekurave area, especially Mertur glacier, have always been in good condition in the last years (even in 2012 and 2016). This is due to their high altitude, and, possibly due to much higher precipitation (probably around 3000 mm/year), a result of their southern position and greater proximity to the Adriatic.

The different trends in small glaciers in the Western and the Eastern Balkans, which were observed in the last two balance years (2014/2015 and 2015/2016) can be explained with some synoptic events of accidental character that affected unevenly the territory of the Peninsula. After a relatively snowless winter, in the beginning of March 2015, a cyclone coming from Greece reached Southern Bulgaria and deposited abundant snow in high mountains, triggered avalanches and piled more than 10 m of snow over Snezhnika and smaller but still amount over Banski suhodol (as it is less prone to avalanche). At the same time, mountains in the western part of the Peninsula did not face that cyclone and remained with little snow. After the summer, melt resulted in a positive balance for Snezhnika, a slightly negative for Banski suhodol and a strongly negative for all glaciers in the Western Balkans. Similar situation occurred also after the next winter.
