DYNAMICS OF PERENNIAL SNOW PATCHES OF MONGUN-TAIGA
MOUNTAIN MASSIF.
D.A. Ganushkin
Saint-Petersburg State University, Saint-Petersburg, Russian Federation
Faculty of Geocraphy and Geocology, St. Petersburg State University, St. Petersburg 199178, 10
liniya, 33/35 Vasilievsky ostrov
Ganushkinspbgu@mail.ru
Abstract.
Perennial snow patches of Mongun-Taiga mountain massif (south-western Tuva, Russia), their
morphology, present state and dynamics over the last 40 years for two time points – 1966 and 20072008 are considered. By 2008 the number of snow patches reduced 4-fold, their area 15-fold.
Contrasts in aspect distribution of snow patches grew, snow patches on western slopes disappeared.
The altitudinal belt of snow patches moved 300-400 m up. Diversity of morphological types also
reduced. The main cause of degradation of snow patches of the massif is decrease of precipitation.
Introduction
According to definition of V.M. Kotlyakov [1] a snow patch is an unmoving mass of snow and ice
remaining on the surface after complete melting of surrounding snow cover. There are three types of
snow patches according to duration of their existence: spring, summer and persistent snow patches.
Persistent snow patches are subdivided into the ones that exist at least one warm season and
perennial snow patches (indefinitely long). There are has several reasons to study perennial snow
patches and their dynamics.
First, snow patches show quick reaction on climatic change, being even more definite indicators of
changing climate than glaciers. Altitudinal interval of perennial snow patches corresponds with
particular combination of temperature and precipitation, its movement up or down shows the
climatic trend.
Second, snow patches are a necessary stage between seasonal snow cover and existence of glaciers,
being “embryos” of the glaciers, on the contrary small glaciers can transform into perennial snow
patches, and they turn into summer snow patches etc., so these processes are reversible
Transformation of glaciers into snow patches and back is sometimes rapid and abrupt, it can lead to
quick changes of the area of glaciation of a mountain region, at the same time total area of surface
of snow and ice (including snow patches) may change not so sufficiently. This is why disregard of
snow patches can cause major distortion of real volume and area of snow and ice.
Third , like glaciers, snow patches are a source of water and may play important role in formation of
runoff.
Fourth, the existence of snow patches is not only the result of particular combination of temperature
and precipitation, but also combination of climatic condition with relief, because snow patches
prefer uneven and contrasting places with shadow and high concentration of snow. Location of
snow patches is deliberate, often it is inherited from previous more cold epochs, when glaciation
was bigger and its erosion and accumulative activity increased contrasts of relief. The result of this
activity of glaciers is creation of such forms of relief as moraine ridges, thermokarst depressions,
marginal channels, rock bars etc., which are often used by snow patches. This helps in interpretation
of these forms in aerial and space photos and makes easier their diagnostics in paleogeographical
reconstructions. Snow patches not only adapt to relief but also change it themselves, increasing its
abruptness and contrasts, creating such negative forms of relief as nival niches and nival corries.
Mongun-Taiga mountain massif (3970.5 m) is situated in south-east periphery of Russian Altai. The
massif has both modern glaciation complex and well-developed altitudinal belt of snow patches.
Glacial and periglacial zone of the massif is studied by geographers of St. Petersburg since 1960-s.
Major changes and tendencies taking part in glaciation of the massif in the last 15 years are even
more obviously indicated by changes in the zone of snow patches which are more vulnerable to
climate change. The need to study snow patches, their spatial distribution and their dynamics is
determined by the rarity of the net of meteostations and lack of meteostations in the high-altitude
zone of the region. Besides, snow patches play important role in the overland flow and in the rate of
stream flow in this arid region.
Main arguments.
This work is dedicated to perennial snow patches of the massif and their dynamics from the period
of cooling in the middle of the 1960-s (aerial photo interpretation and analysis of photographs) till
warm and extremely dry period of 2006-2008 (direct observations). Comparison of two opposite
states of snow patches of the massif shows not only general trend of changes of snowiness but also
the range of climatic fluctuations.
Concerning Mongun-Taiga massif it is possible to say about several morphological types of
perennial snow patches, in general corresponding with classification of V.P.Tirishkanov [2], based
on study of snow patches of western part of Katunsky mountain ridge. In our classification we tried
not only to show genesis of the form of relief, containing snow patch, but also the location of snow
patch with reference to the slope: 1. snow patches (s.p.) of peneplanation surfaces (flat watersheds),
situated higher than others; 2. s.p. of the edges of plateau, in the upper parts of steep slopes of the
edges of peneplanation surfaces; 3. crest snowdrift s.p.; 4. periglacial s.p., they exist due to high
concentration of snow on or under steep fronts of glacier tongues, as glaciers retreat these s.p. stick
together with the edge of the glacier, sometimes complicating the process of finding the one (we
observe this picture, for example, near the edge of corrie glacier Eastern Baliktig); 5. S.p. of modern
moraine relief (this means s.p. on the surface of moraine complexes, formed by uncovered by soil
and vegetation and well-defined in relief moraine mounds of little ice age and adjacent younger
oscillation mounds, seen up to modern glaciers); 6. hanging s.p., located on steep parts of most
high slopes; 7. s.p. of watershed slopes, on slopes of average and little steepness within smoothed
watershed areas; 8. erosional s.p. in channel areas of temporary streams; 9. lakeside s.p., taking low
parts of lake depressions; 10. s.p. of the foot of the slope (s.p. of avalanche cones), they have mostly
avalanche accumulation; 11. corrie s.p., usually large, located on the bottoms of corries; 12. s.p. of
trough valleys, they exist due to high concentration of snow in intermoraine depressions on bottoms
of trough valleys
We did not include snow patches of glaciers into this classificatioin, because location of firn patches
on glaciers and their accumulation zones are a separate question and it needs special attention.
Among these types of snow patches there are three groups of morphological types of snow patches
within the massif according to their location: 1. at the foot of the slopes or on the bottom of the
valleys (niche, periglacial, moraine relief, erosion, lakeside, corrie and trough snow patches); 2. on
steep slopes of trough valleys (plateau edge, hanging and crest snow patches); 3. on watershed
surfaces (peneplanation plane and slope snow patches).
According to our reconstruction in 1966 there were 799 perennial snow patches with total area
about 14.7 km2 in the massif; they were mostly located on eastern and south-eastern slopes (45% of
total area, tab.1). Almost half of the total area of snow patches belonged to the first group of
morphological types. Snow patches located in glacial forms of relief prevailed.
Aspect
N
NE
E
SE
S
SW
W
NW
Number of snow patches
134
203
153
100
64
59
25
61
Table. 1. Aspect distribution of
%
16.8
25.4
19.2
12.5
8.0
7.4
3.1
7.6
Total area, km2
1.4
3.0
3.4
3.2
1.3
1.0
0.2
1.2
%
9.5
20.2
23.0
22.0
8.7
7.0
1.6
8.1
perennial snow patches of Mongun-Taiga massif in 1966.
Altitudinal interval of existence of snow patches was 1370 m (from 2470 m to 3840 m over the sea
level). There were two special features in the way of spatial change of level of lower limit of snow
patches. First, his level elevated fron north-west to south-east of the massif from about 2500 m to
3000-3300 m, it is because most part of precipitation in the massif comes with intrusions of cold air
from the north-west. Windward slopes of the main watershed of the massif get more precipitation,
on the contrary south-eastern periphery is in the wind shadow of the watershed. Second, slopes of
north aspects were most favorable for snow patches, south-western slopes were least favorable.
Difference in height of lower limit of snow patches on the opposite slope of the same mountain
crests was 300-600 m for the northern and southern slopes.
Position of the upper border of existence of snow patches was limited by several factors: height of
mountain ridge, lower limit of glaciation and also by very steep slopes in the altitudinal interval of
3300-3700 m. Existence of glaciers as a factor, limiting spatial distribution of snow patches leads
to big difference (up to 600 m) between the upper limit of snow patches on north-eastern and southwestern slopes with glaciation (fig. 1).
In simplified variant the altitudinal belt of snow patches of the massif can be shown as the zone
between the average altitude of the lowest points of snow patches and the average altitude of the
lowest point of glaciers (limiting the snow patches “from above”). In the middle of 1960-s this belt
had the lowest position on north-eastern slopes and on the south-western slopes – the highest. On
south-western slopes, though they had the least concentration of snow, it also had the maximal
vertical diapason. It was caused by very small areas of glaciation on these slopes, which left enough
space for snow patches on the highest parts of the slopes.
Figure. 1. Altitudinal snow levels on slopes of different aspect in 1966 г. 1- firn line on glaciers, 2average altitude of the lowest points of glaciers, 3- average altitude of the lowest points of snow
patches, 4- minimal altitude of snow patches.
Sufficient altitudinal diapason of existence of snow patches in the middle of 1960-s in combination
with complicated relief of the massif determined diversity of morphological forms of snow patches
(tab. 2).
The most favorable conditions for snow patches were at low levels in negative glacial forms of
relief. Concentration of snow in corries, on the bottoms of troughs, at the edge of the glaciers was
caused by avalanche activity, intensive enough in the middle of 1960-s.
Group of
morphological types
Morphological
type
Foot of the slopes or Erosional
bottom of the valleys
Moraine relief
Lakeside
Trough valleys
Of the foot of the
slope
Corrie
Periglacial
total
Steep slopes of trough Hanging
valleys
Of the edge of
the plateau
Crest snowdrift
total
Watershed slopes
Of
watershed
slopes
Of peneplanation
surfaces
total
Number Area,
km2
27
0,48
the average
altitude of the
lowest point, m
2781
the average
altitude of the
highest point
2878
107
4
8
116
0,85
0,02
0,98
0,99
2728
2671
2813
2791
2738
2677
2904
2857
70
2,93
2877
3030
12
0,25
3058
3175
344
137
75
6,45
1,70
1,13
2950
3062
3170
3138
43
255
159
0,96
3,79
3,60
3058
3153
2974
3034
41
0,81
3117
3182
200
4,41
Table 2. Morphological types of snow patches of Mongun-Taiga mountain massif in the middle of
1960-s
By 2006-2008 the number of snow patches became 4-fold and the total area – 15-fold less than in
1966 (fig. 2). Glaciation of the massif at the same period lost only 30% of its area, showing slower
reaction to climate change. Less than a half of the total area of perennial snow patches in 2006-2008
belongs to the ones that survived from the middle of 1960-s, the others appeared as a result of
disintegration of glaciers and their firn fields.
Figure 2. Dynamics of perennial snow patches in 1966-2008 (central fragment of the map) . 1mountain peaks, 2- mountain ridges, 3- rivers, 4- lakes, 5- modern glaciers, 6- snow patches in
1966, 7- snow patches in 2006-2008.,
Contrasts in aspect distribution of snow patches increased – the share of snow patches on leeward
slopes (north-eastern, eastern, south-eastern) in the total area changed from 65% to 72%, the share
of snow patches on western slopes reduced from 12% to 4.5%. To estimate contrasts in aspect
distribution of snow patches we used coefficient of aspect contrast:
m
K
S S 
2
i
i1
0
(m mS
)
2
, where K - coefficient of aspect contrast, Si - value of parameter estimated,
2
0
S0 - average value of the parameter provided that the aspect distribution is even, m - number of
bearings
In 1966 coefficient of aspect contrast was 0.21 for the number of snow patches and 0.23 for the
area. In 2006-2008 these numbers increased to 0.28 and 0.38.
By 2006-2008 the altitudinal zone of snow patches rose about 300-400 m, its lower limit reached
the average level of glacial termini, snow patches survived only in the areas between glacier
tongues (fig. 3).
Figure 3. Altitudinal snow levels on slopes of different aspect in 2006-2008. 1- firn line on
glaciers, 2- average altitude of the lowest points of glaciers, 3- average altitude of the lowest points
of snow patches, 4- minimal altitude of snow patches.
Variety of morphological types also reduced (tab. 3).
Group of
morphological types
Morphological
type
Foot of the slopes or Erosional
bottom of the valleys Moraine relief
Of the foot of the
slope
Corrie
total
Steep
slopes
of Hanging
trough valleys
Of the edge of
the plateau
Crest snowdrift
total
Watershed slopes
Of
watershed
slopes
Of peneplanation
surfaces
total
Number Area,
km2
7
10
4
0,03
0,03
0,02
the average
altitude of the
lowest point, m
3014
3119
3168
18
39
60
38
0,12
0,20
0,24
0,16
3228
3132
3306
3290
3290
3178
3402
3326
24
122
37
0,04
0,45
0,36
3340
3200
3288
3378
3249
3320
2
less
than
0,01
0,36
3385
3415
3337
3368
39
the average
altitude of the
highest point
3086
3146
3189
Table 3. Morphological types of snow patches of Mongun-Taiga mountain massif in 2006-2008.
Periglacial, lakeside and trough snow patches disappeared. Disappearance of periglacial snow
patches was caused by flattening of glacial termini, which caused lower accumulation of snow at
their edges. Lakeside and trough snow patches melted down because of their low level.
Dynamics of firn line on glaciers of the massif corresponds well with the shift of the altitudinal
belt of snow patches. In the middle of 1960-s weighted average altitude of firn line was 3350 m ,
firn line was seen on all the glaciers of the massif. In 2006-2008 firn line rose to the level of 3595
m, firn remained not on every glacier of the massif, and former united accumulation zone of the
glaciers belonging to the complex of the main mountain peak transformed into a group of firn
patches, so level of 3595 m is only the level, over which more than 50% of the glacial surface IS
covered by firn. In fact, these firn parches are a kind of perennial snow patches, but on the ice
surface. 50-150 m less elevation of firn line in comparison with elevation of snow patches must be
caused by cooling effect of ice surface.
In the period 1966-2008 elevation of firn line was about 250 m, it matches with 1,5°С rising of
summer temperature on the background of the same as now precipitation (proceeding from
altitudinal gradient of temperature 0,6°С/100 m), or 450 mm decrease of annual precipitation
(according to M.V. Tronov 180 mm per 100 m of change of level of snow line in case of constant
temperature [3]). Sufficient decrease of precipitation is confirmed by observations, though with
annual precipitation a little over 300 mm at the altitude of main mountain peak of the massif and
l50-200 at the foot of the massif absolute value of decrease coul not be so big. Probably this rule
does not work in most arid areas of Altai, also the same absolute value of decrease of precipitation
on different altitude is doubtful because dependence of precipitation from altitude is curvilinear.
It should be noted that rapid increase of, accumulation of snow since 2009 led to recovery of snow
patches at the levels of the middle of the 1990-s, which is appropriate to intermediate state between
the state of snow patches in the middle of 1960-s and 2006-2008.
Analysis and comparison of the changes of the altitude of firn line and of perennial snow patches in
the last 40 years lets us make a conclusion that in case of short climatic fluctuations vertical
diapason of changes of the altitude of the belt of snow patches is 50-150 m bigger than the one of
firn line on glaciers because snow-firn fields in accumulation zones of the glaciers, being larger,
have longer period of reaction and do not have enough time to respond on short climatic
fluctuation. At the same time glaciers, as the most large-scale among these objects is even slower
and it corresponds with calculated change of the snow line which is 180 m less than the elevation
of firn line which is observed on the glaciers.
The pattern of changes shows that in the modern period of unfavorable climatic conditions snow
patches located on steep slopes prevail. These snow patches exist due to snow drifting and
concentration of snow on leeward slopes. Reduction of snowiness reduced avalanche nourishment
and degradation of trough, corrie and niche snow patches. This process, as well as increase of
aspect contrast indicates aridization of climate. Aridization and warming are indicated by the move
of the zone of snow patches and also by rising of firn line on the glaciers of the massif (about 250 m
from the middle of the 1960-s).
Bibliography.
1. Kotlyakov V.M. (2004) Izbrannie sochineniya v shesti knigah. Kniga 2. Snezhniy pokrov I
ledniki Zemli. –Moskva: Nauka, 448 s.
2. Tirishkanov V.P. (1976) Morfologiya snezhnikov zapadnoi chasti Katunskogo hrebta //
Glyatsiologiya Altaya, vip. 11, . S. 98-102.
3. Tronov M.V. (1978) Problema glyatsioklimaticheskikh pokazatelei. Tomsk: Izd-vo Tomskogo unta, 166 s.