Snežišča v Julijskih Alpah

Abstract

the Julian Alps, where the peaks reach the heights of over 2400 m,
as an exception also where they reach at least 2300 m (Kriška stena,
Bovški Grintavec). In contrast to the Triglav group, where ali snowfields are under peaks of more than 2500 m, there are snowfields also
under the peaks above Trenta, Planica, Bavščica valleys, which are
only about 2300 m high (Sita, the ridge of Bovški Grintavec). In the
Triglav group, which has somewhat plateau like character, snowfields
exist also on the peaks themselves. In the western Julian Alps (on
jugoslav side), however, being much more indented, the snowfields
are much more concentrated to the foot of the steep north walls or to
deep ravines.
With regard to form and site, the snowfields can be classified
into several types:
1. The slope type. The only snowfield of this type is that one above
the Triglav glacier.
2. Snowfields on talus slopes under more or less smooth rockwalls (Zaplanja, under the east wall of Mali Triglav). These snowfields
are comparatively wide-spread, but not thick and are subject to great
seasonal shrinking, because the large surface is exposed to influences
of the air and radiation. Such snowfields are permanent only in greater
heights. Their existence is more dependant on the oscillation of the
radiation than on the mere amount of precipitation.
3. Snowfields in deep, narrow and steeply inclined ravines on the
mountain-side (Jalovčev žleb, Loški žleb, Špikov graben). Snowfields
which are more open have a maximum incline of 35—40° (this is
explained by the fact that the snow tends to glide downwards if the
incline is greater). Those snowfie!ds, lying in very narrow ravines,
however, can persist at an even greater incline. Ali snowfields of this
type lie in extremely shadowy sites. Their length is subject to great
fluctuations. Small icefields occur only within this type.
4. Snowsfields in cirques and in other similar depressions (Amfiteater, Velika Dnina, Pekel, Triglavski prodi). These can be found only
in greater heights, particulary around Triglav and Škrlatica. The mass
of snow is quite substantial and wide-spread.
5. Snowfields under steep ravines. The mass of snow accumulates
at the lower end, in the bottom, often on talus slopes and has the
characteristic form of a truncated cone or truncated pyramid (under
the north wall of Rjavina, under the ravine on the north side of
Jalovec), Because only a small surface is exposed to sun and air, it is
supposed, that fluctuations in size are due most of ali to the avalanches
and snowfall. With the type 4., the surrounding steep walls have a height of
200—400 m, and with the type 5. lying in the lowest possible altitudes,
the walls reach a height of at least 800 m.
Comparing data about the size of the snowfields in the beginning
of this century and those for the last few years, the author could find
that a general shrinking of the snowfields has not been equal in čase
of ali types presented above. A considerable shrinking and diminishing
has occurred in the snowfield above the Triglav glacier, in the Bovec
sneg, on Triglavski prodi, in Pekel, in Amfiteater and perhaps at Pri
Jezercih under Jalovec. In these places some previous permanent
,snowfields now disappear during the summer. Ali the snowfields
rmentioned just before are more than 2000 m above sea level and lie
in karstic depressions or in cirques. Only in some exceptional cases
they belong to the second type and lie on talus under precipitous walls.
A comparison of the snowfields lying at the lowest altitudes leads to
no accurate conclusions. It is supposed that the snowfield under Loški
žleb has been greater in 1952 than fifty years ago. Therefore one is
justified to make the conclusion, that in the Julian Alps the higher
snowfields have shrinked more than those lying in lower altitudes.
In light of the characteristics of the snowfields of the five types
it is possible to give some judgement on the question whether the
existence of the snowfields is due primarily to the amount of precipitation (Manohin) or, to the radiation and temperature of the air.
If the amount of snow would be of paramount importance, the snowfields under deep ravines, most dependant on the supply of snow by avalanches and lying at the lowest altitudes, had to shrink most in čase
of a diminished snowfall. It was found, however, that those snowfields
lying in the greatest altitudes have shrunk most, inspite of the fact
that there radiation and air temperatures are necessarily much more
intensive because these snowfields also enjoy less shade than those in
lower areas.