Researches of Field Evidence for Late Quaternary Climate Changes in the Highest Mountains of Bulgaria - Sustainable Development in Mountain Regions: Southeastern Europe - page 149

to embryonic forms of glaciation (i.e. the present Equilibrium line altitude in Rila
is not far above the highest peaks), and a small but continuous drop in temperatures
will cause formation of such. However, for the period of instrumental observation
(1933-2008) temperatures at Musala peak were ranging between -1.7 and -4.0 ◦ C
and showed general trend of warming, although there was a shift of four contrast-
ing short-term trends - towards a decrease (in the 1930s and 1940s), an increase
(1940s-1960s), a decrease (1960s-1970s) and a period of sufficient increase (since
1980). Average annual temperatures at Musala have shown a cyclic variation in a
range of about 0.5-1.5 ◦ C with duration of 3-5 years. In general, when looking at
sliding averages (10 year intervals) appeared that the rise of temperature for 1998-
2008 compared to 1933-1943 has been about 0.5 ◦ C, and for 1998-2008 compared
to 1958-1968 has been about 1.0 ◦ C(Nojarov, 2008 ).
Although there are no measured data in Bulgarian high mountains before 1933,
regional climatic evidence surely indicates that climate was much colder in about
1910 and suggests that long-term average temperatures were more than 1 ◦ Clower
than at present and this should be considered as a maximum temperature for
formation of perennial snow patches in the higher areas of Rila mountain.
Clear traces of bigger extent of the embryonic forms of glaciation can be
observed also in Pirin, in Golemia Kazan cirque. Snezhnika microglacier is sur-
rounded by a well-outlined moraine ridge situated at some distance away from the
present ice margins even in years when the size of the firn body during minimum
is relatively high. As already mentioned (Grunewald et al., 2008 ), the crest should
have been formed in its present shape during the LIA. Such a hypothesis is sup-
ported by the state of the lichen cover on the crest (partly but evenly developed),
which indicates that at present the ice margin during minimum never reaches the
crest (no fresh material has been added), and, on the other hand, no other moraine
ridge is observed further down the cirque bottom - the next ridge in sequence is
quite old (weathered, corroded and covered entirely by lichen), with undoubtedly a
several thousand year old in age (most probably Würmian, as first stated by Popov,
1962 ). As in Rila, this bigger extent of Snezhnika in the past is a result of climate
conditions with lower annual temperatures and probably higher precipitation. The
role of each of these climatic factors over extent of glaciation is hard to differentiate,
but it is sure that they both are of great importance. The influence of temperature
on the dynamics of perennial snow patches can be clearly seen making a compar-
ison between the size fluctuations of Snezhnika in the last several decades and air
temperature (Fig. 12.7 ).
12.5.2 Monitoring of Present Geomorphic and Hydrological
Processes
In 2003 the Institute of Geography launched the project “Models of contemporary
periglacial morphogenesis”, in which a detailed 3-year observations were planned
to be carried out on a comparative basis in four key areas - Musala area in Rila