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4Гляциология
Гляциология
Glaciology
https://doi.org/10.55764/2957-9856/2022-3-3-14.13
УДК 551.324; 551.583
M. A. Petrov1, G. E. Glazirin2 , I. G. Tomashevskaya3,
A. A. Tikhanovskaya , T. Yu. Sabitov
1 Candidate of geol.-min. sciences, Senior Researcher, Head of the Center of Glacial Geology (Institute of Geology and Geophysics, Goskomgeology, Tashkent, Uzbekistan)
2 Doctor of Geographical Sciences, Professor (Institute of Geology and Geophysics, Goskomgeology, Tashkent, Uzbekistan)
3 Candidate of geographical sciences, Senior researcher (Institute of Geology and Geophysics, Goskomgeology, Tashkent, Uzbekistan) 4 Senior Researcher (Institute of Geology and Geophysics, Goskomgeology, Tashkent, Uzbekistan) 5 Candidate of geographical sciences, Associate Professor (M. Ulugbek National University of Uzbekistan, Tashkent, Uzbekistan)
INFLUENCE OF THE MODERN CLIMATIC SETTING IN THE MOUNTAINS OF CENTRAL ASIA ON THE STATE OF GLACIATION, GLACIER RUNOFF AND GLACIAL LAKE OUTBURSTS
Abstract. The climatic setting of Central Asia in the second half of the 20th century and in the first decade of the 21st century is characterized by a change of horizontal and vertical temperature gradients at the western periphery of the Central Asian mountain system. The growth of summer air temperatures led to the decrease of mountain glaciations. In the last 45 years the glaciers in selected catchments of Gissar-Alay lost about 16% in area while the glaciers of the Pskem river catchment lost 27% in area. The river regimes, primarily the annual distribution of runoff react to the glacier decrease. The share of glacial runoff is over 25% in years with little precipitation, while it considerably decreases in years with abundant precipitation. One of the negative consequences of the glacier dectrease is the formation of lakes in the periglacial area. The state of glacial lakes should be monitored, because they may pose outburst debris flow hazard.
Keywords: Climate change, change in glacial runoff, formation of glacial lakes, reduction of glaciation in Central Asia.
Introduction. Climate is one of the main factors forming water resources of areas including river runoff, glaciers and lakes, which in turn determine activity of such a negative natural phenomena as landslides and glacial mudflows. Present time climate change is evident worldwide. The purpose of this work is to assess this change for the Central Asia territory and particularly for the basin of Pskem River, right tributary of Chirchik river, which belongs to the Western Tian-Shian Mountain system. It is necessary to emphasize that Pskem River basin is politically and economically important region of Uzbekistan Republic.
The first catalogue of the Central Asian glaciers was based on the data for the year 1930 and included 1223 glaciers (45 from them belonged to the Pskem River basin) with the variation of the low boundary from 3058 m up to 3942 m [1Korzhenevskiy, 1930]. The results of glaciological investigations for the years 1930-1957 and data obtained during International geophysical year (IGY, 1957-1959 years) were summarized in multivolume publication "Catalogue of the glaciers of USSR". One of its volumes is dedicated to the Pskem River basin. At the time of the catalogue publication the number of glaciers in the
Pskem River basin was 250 with the total area of 127,8 km2 [2 Catalogue of glaciers of USSR, 1968]. Since 1961 Institute of mathematics of Academy of Sciences of UzSSR (Institute of Geology and Geophysics of Academy of Sciences of UzSSR since 1991) and Hydrometeorological service of UzSSR (Uzgidromet and NIGMI, RUz) carry out occasional ground and aero visual observations in the upper reaches of Pskem River. Results of this work are important for the prediction of changes of the ecological situation in the region, as Pskem River is a main source of water, which supplies hydroeconomics of Tashkent, the capital of Uzbekistan with population of 3 million, as well as many other settlements, industrial and energy enterprises, vast farmlands.
Used data and methods. Long-term background of a general hygrometeorological situation in the mountain and plain area of Central Asia (37,7° - 42,2° N) was described by many authors, for instance [3 Glazirin G.E., Tadjibaeva U.U., 2011; 4 Glazirin G.E., Gavrilenko N.N., 2013]. The data of deviation of annual precipitation and average annual temperature from long-term mean (1961-1990) on 50 hydro-meteorological stations located in the different physic-geographical conditions are used for analysis of the change of climatic situation in Uzbekistan [5Spektorman T. Yu., Petrova E.V., 2007]. Change of the climatic characteristics (precipitation and air temperature) of the specific basin of Pskem River (Syrdarya river basin) were considered for 1930-2010 along the longitudinal profile from lowland meteorological station Tashkent (H=478 m) through the Pskem river valley (meteorological station Pskem, H=1256 m) up to upper reaches of Oigaing river (Oigaing meteorological station, H=2151 m) (figure 1). Change of annual values were assessed together with change of values averaged over the seasons: winter (December, January, February) - the most wet period, summer (June, July, August) - period of active ablation. Average air temperatures observed during 1970-2008 on the meteorological stations Tashkent, Pskem, Oigaing were also used. Index of continentality (Kk) [6Chromov S.P., Petrosiants M.A., 1994] and Index of active surface wetness (Kwet) [7 Mezentsev B.C., Karnatsevich I.V., 1969] were calculated for the area of Uzbekistan, as well as their variation with altitudes from lowland part (Tashkent meteorological station), over sub-mountain region (Pskem meteorological station) and up to middle altitude (Oigaing meteorological station).
Figure 1 - Map of the reference meteorological stations (MS) Tashkent, Pskem and Oigaing (inset)
1. Climate characteristics. Annual air temperature and precipitation. Long-term changes of meteorological values (mean summer air temperature and annual precipitation for the altitude over 1500 m a.s.l.) were analyzed for unbiased assessment of regional climate change in the area of Central Asia [4Glazirin G.E., Gavrilenko N.N., 2073]. It became apparent that horizontal and vertical temperature gradients change in time on the western periphery of the Central Asian mountain system. Winter temperature rises much faster than summer one in the area of Central Asia, whereas annual precipitation do not change, or rise negligibly. Average change of annual precipitation for all the stations is associated with change of summer air temperature: the air temperature decreases when precipitation amount increases. Rise of precipitation trend was observed for all the altitudes west-to-east (figure 2) [5 Spectorman T.Yu., Petrova E.V., 2007].
Trend,%
1,2 -
1 - ♦
0,8 - ♦
0.6 -
0.4 -
0,2 - + Latitude, deg.
n ♦ ♦
r 1 1 1 1 1
-0.2 3 7 * 38 39* 40 41 42 43
-0.4 -
Figure 2 - Dependence of relative linear trends of annual precipitation on altitudinal situation of the station
For the Republic of Uzbekistan the trend of air temperature increased monotonously while precipitation remained unchanged (figure 3).
2 1,5 1
0,5 0
-0,51 -1 -1,5
-2 -2.5
dT.-C h ill
S30, . /940 yWo li 1W l\j 1980 199ÜW 200a Years
Figure 3 - Deviation of average annual air temperature (dT) and annual precipitation (dP) from long-term mean value
for 1961-1990 in Uzbekistan
For the longitudinal profile of the annual air temperature, change averaged over decades (T10) on the plain as well as on the middle altitudes proceeded non-monotonic with trend increasing during 1998-2010 (figure 4, table 1).
Figure 4 - Change of T10 value during 1980-2010
The graphs of the change of value dT = T2-T1 were drawn to identify annual variation of changes of air temperature between the periods of 1970-1998 (period 1) and 1998-2010 (period 2), where T1 and T2 are average air temperatures for each month of the corresponding period (figure 5).
Figure 5 - Annual variation of the dT value; Pskem river basin
Analysis of the annual air temperature variation indicated that main increase of air temperature (up to 3°C) fell on spring months, March particularly. During winter months, the air temperature was increasing faster on the plain than in the middle altitude zone. Since last decade winters became warmer in whole profile, the trend of summer air temperature was significantly lower than one observed in winters.
In the Pskem River basin change of winter precipitation with the altitude is not monotonous (table 1). This deviation disappears during the summer. Decrease of annual and winter precipitation is observed from Pskem MS to Oigaing MS. The same time the main amount of winter and annual precipitation is in the middle altitude zone (MS Pskem). Let us summarize foregoing analysis of climatic situation change. The main conclusion is following: in the territory of Central Asia including plain and mountain part of Uzbekistan air temperature increases while precipitation remain almost unchangeable.
Table 1 - Average annual precipitation amount (mm), 1970-2010
Station ЕХ year ЕХ (X-II) ЕХ (VI-IX)
Tashkent 426 235 23
Pskem 858 478 87
Oigaing 738 372 121
Climate of Uzbekistan is sharply continental and characterized with low humidity. Calculated indices of continentality (Kk) and active surface wetness (Kwet) allow tracing their change along the longitudinal profile from lowland up to mountain area. Climate continentality decreases with altitude, that is associated with decreasing of air temperature and increasing of precipitation amount (figure 6).
Figure 6 - Change of Kk with an altitude
The area of the Republic is characterized with a deficient humidity excepting Tashkent oasis and foothills, however the calculations show some increase of the active surface wetness (Kwet) in the middle altitude last years (figure 7).
Figure 7 - Change of the Kwet index from lowland up to middle altitude
2. Change of glaciation. Change of climate characteristics in the region has an impact on glaciation size as well as ice melting in the summer. General processes [8 Petrov M.A., 2001] occurring when glaciation shrinks are following:
1. Disappearance of the glaciers of an area under 1 km2.
2. Disintegration of large glaciers and tributaries separation.
3. Decreasing of glaciation coefficient at the expenses of accumulation area reduction.
4. Increasing of moraine area and natural pollution of glaciers.
In the work [9 Konovalov V.G., Viliams M.V., 2005] dependence of the relative rate of the glaciation area decrease dF/dt in the basins of Central Asian rivers on accumulation area index Kac is presented. Accumulation area index shows relation between accumulation area (Fac) change and area of whole glacier or total area of glaciation (Fgl): Kac = Fac/Fgl. Even in case of equality of accumulation and ablation areas, steady decrease of the Central Asians glaciers size occurs with a rate of about 0,5% of the initial glaciation area per year.
As an example, table 2 contains change of total glaciation area and the area of moraine cover during degradation of glaciation in the area of Pamir and Gissar-Alay [10 Schetinnikov A.S., 1981].
Table 2 - Reduction of the total glaciers area in the area of Central Asia (Fgl - glaciation area, Fm - total area of glaciers covered with moraine)
Pamir Gissar-Alay
Years Fgl, km2 Fm, km2 Years Fgl, km2 Fm, km2
19б1 73б0 420 1957 2180 1б7
1980 бб00 б40 1980 1840 200
2005 (5770)* 2005 (1470)*
%/year 0,52 %/year 0,81
* Data calculated by Glazirin G.E.
TERRA-ASTER based use of space images allowed to assess the glaciation state in the mountain system of Gissar-Alay and to compare rates of glaciation degradation for the periods of 1957-1980 and 1980-2001 [11 Yakovlev A., Batirov R., 2006]. During the period from 1957 till 1980 most of Gissar-Alay glaciers of the area 2-5 km2 lost significant part of their area. Changes of the glaciers of area under 2 km2 is less noticeable. According to the data for 2001 the total area of investigated glaciers of Gissar Alay (Shakhimardan, Sokh, Isfara rivers basins and the system of Zeravshan glacier) made up about 480 km2. In 1980 and 1957 the total area of the glaciers was 511 km2 and 570 km2 respectively. Authors state that during 1980-2001 the number of large glaciers in these basins decreased at the expense of their disintegration and a number of smaller glaciers increases. This case increasing of moraine cover of the glacier tongue delays glacier surface melting, that leads to decreasing of degradation rate: from 0,46 % per year to 0,27 % per year (table 3).
Table 3 - Annual rate of the glaciation degradation
Basin Glaciation area, km2 Average rate of annual glaciation degradation, %
1957 1980 2001 1957-1980 1980-2001
Shakhimardan 39,4б 30,14 28,19 1,03 0,31
Sokh 24б,2б 214,б3 198,25 0,5б 0,3б
Isfara 129,74 125,05 120,99 0,1б 0,15
Zeravshan 15б,57 141,б2 135,10 0,42 0,22
Total 572,03 511,44 482,53 0,4б 0,27
Approximately the same rate of degradation for the account of moraine cover increase is typical particularly for the Zailiysky Alatau region (Northern Tian Shan) [12 Vilesov E.N., Uvarov V.N., 2001]. E. Semakova point out decreasing of the degradation rate of glacial basins of Uzbekistan since last decades [13 Semakova E., Gunasekara K., Semakov D., 2015], that can be caused particularly by some
diminution of climate continentality since beginning of 80ths up to 2005 (Fig. 6). The period of 1971-1980 was the driest and hotest, that affected degradation rate. In the mountain regions of Gissar Alay (Tajikistan) A.F. Finaev point out stabilization of glaciation and even it's increasing at the expense of precipitation increase during the period 1992 -2010 [14 Finaev A.F., 2013]. However the rate of glaciation degradation remains high in the most of the world mountain systems, and "since last decade it increased significantly, especially in the continental dry and polar regions (mountain of Central Asia, Alaska, the Rocky Mountains and Cascade Range), that is in agreement with tendency of air temperature increase and annual snow accumulation decrease" [15 Kotliakov V.M., Seversky I.V., 2013].
In whole climate situation in the second part of XX century was unfavorable for the existence of glaciation in Gissar-Alay and in Pamir-Alay in total. According to [2Catalogue, 1968] and [16 Semakova E.R.., Semakov D.G., 2014] glaciers of the basins of investigated Gissar Alay rivers lost about 16% of their area since last 45 years, and area of glaciation of Pskem river basin decreased by 27% of the area estimated in 1960 (table 4).
Table 4 - Change of the total glaciation area (Fgl) in the Pskem River basin
Year Fgl, km2 Source of data
1960 127,8 [Catalogue., 1968]
2010 93,6 [Semakova E. R., Semakov D.G., 2014]
1970 219,8 [Narama Ch., Kaab A., Duishonakunov M., Abdrakhmatov K., 2010]
2007 168,7 [ibid.]
According to the data [17 Narama Ch., Kaab A., Duishonakunov M., Abdrakhmatov K., 2010] aggregated area of glaciation in the Pskem River basin in 1970 and 2007 differs from the sources listed in the Table 4. The possible reason of this difference between areas is geographical coverage of the area. The glaciers of the Pskem River basin were considered in the works of E. Semakova. Run off from the glaciers remains in the area of Uzbekistan. All the glaciers of the region are included into calculation [17Narama Ch., 2010] and the runoff from some of them goes over the border. Secondly, initial data used by the authors are different: E. Semakova, etc. compared data of space images with data from Catalogue 1968; Narama Ch. etc. used Corona space images for 1967-1970. Apart from these reasons, one should mention different methods of decoding and different timing.
The altitude of the glacier snout changes when the area of glacier decreases. The dependence of the value AH =Zmax - Hmin (Zmax- altitude of the higher bound of glaciation, Hmin - minimal altitude of the glacier snout in the basin) on the air temperature at the higher bound of glaciation T(Zmax) was found for 27 glacial basins [18 Toychiev Kh.A. etc., 2008].
AH = -160,1 x T(Zmax) + 1237,6; R = 0,927.
In accordance to this formula glaciers tongues "pull themselves up" to the higher bound of glaciation. Calculated value of the rise of glaciers tongues midline for the Pskem river basin is 40-100 m.
3. Glacier-derived runoff. The volume of melt-water from glacier is determined with total glaciation area and summer air temperature. Problem of the impact of reduction of glaciation on run- off volume is discussed. A part of investigators talks about reduction of the melting water contribution in the total runoff of a glacier-fed stream. Another part finds that this portion of the run-off remains constant in spite of glaciers degradation, although rivers' regime, primarily annual distribution of stream flow, certainly responses to the glaciers' shrinking.
It is necessary to emphasize that we use following definition of glacier-derived runoff given by A.S. Schetinnikov: this is a runoff "forming for the account of melting perennial storage of ice and firn (the snow on a glaciers, which does not melt for more a year after falling)" [19 Schetinnikov A.S., 1984]. This definition does not coincide with one given in the glaciological dictionary [20 Glaciological dictionary, 1984], however, in our view, the second one is not applicable for interpreting of glaciers' contribution to annual (and longer) river runoff. V.A. Kuzmichenok [21 Kuzmichenok V.A., 2013] agrees with this. He underlines that definition of glacial runoff given in the glaciological dictionary "is possibly correct from the geometrical point of view, but is not suitable for interpreting of glaciers' runoff
contribution to the annual (and longer) river runoff'. Glacier-derived feeding of rivers is formed for the account of melting of perennial accumulation of snow and ice. A main hydrological role of glaciers is to accumulate annual excess of precipitation and redistribute it's perennial melting.
Increasing of summer air temperature leads to change of base ablation values, i.e. snow and ice melt on the glacier's surface. When glaciation reduces by 30% the volume of runoff is close to norm by warming for 2°C. When glaciation reduces by 40% and more increasing of temperature will not compensate loss of runoff [19 Schetinnikov A.S., 1984]. When calculating ice melting under moraine it was assumed that moraine's average thickness was 10 cm, and the value of the melting was a half of free ice melting. Summer snowfalls impact on ablation is included automatically into the change of summer temperatures.
In the work [22 Glazirin G.E., 2013] the river basins with different glaciation area in different regions of Central Asia were selected for the assessment of long-term average annual part of glacial runoff. The long-term hydrological and meteorological observation data are available for this basin as well as information about change of glaciation based on data from three inventories (Catalogues) of glaciation. The results of calculations are in the Table 5. In the net, impact of glaciation reduction is not significant and fall within the accuracy of annual runoff calculation for the rivers with significant glaciation area at the origin, those runoff measured at lower reaches.
However, the role of glacial runoff in the total river runoff for the summer period of defined year depends on dryness of the year. A year when annual (winter) precipitation is not less than 1,15 of their many-years average (XX10_4I/JX10_4cp > 1,15) can be relegated to high-water years. A year when this relation does not exceed 0,80 (XXi0_4I/£Xi0_4cp< 0,80) is low-water year [23 Tikhanovskaya A.A., Tomashevskaya I.G., 2008]. Sample of the calculations for the particular Oigaing river basin is in the table 5.
Table 5 - Portion of glacial feeding (Qgi) in the summer runoff Q of Oigaing river (August-September)
in high- and low-water years
Year IX10-4 I / ХХ10-4СР Qgi/Q
Low-water years
1961 0,53 25,6
1980 0,73 20,1
High-water years
1969 2,12 11,4
1987 1,44 13,9
Hence, portion of glacial feeding in summer months of a low-water year can form up to 25% of the total river runoff, decreasing down to 10-12% in a high-water year.
Table 6 - Assessment of the annual portion of glacial runoff
River Station Area of glaciation in the basin, km2 Long-term average annual Glacial runoff averaged over the Qgl portion in the total Part of the glacial runoff induced by the glaciation Portion of Qg2 in the average
initial final runoff, Qa, m3/sec calculation period, Qgl, m3/sec river runoff, % change, Qg2, and averaged over the period annual runoff, %
Oigaing Mouth of Koksu river 33,8 25,8 12,8 2,71 21,2 0,26 2
Pskem Mullala 114,4 89,4 76,8 9,36 12.2 0,71 0,9
Sokh Sarykanda 246,3 191,9 156 42,8 23,8 7,46 7,3
Zeravshan Khudgif 311,3 268,5 32,8 19,1 58,2 5,40 16,5
Dupli 663,2 537,1 44,2 10,5 27,4 3,22 4,8
Yazgulem Motravn 330,4 262,7 36 7,77 21,6 5,56 15,5
The developed model of the calculation of glaciation and runoff change depending on air temperature (TS) at the upper boundary of glaciation (Zmax) allowed to calculate smallest height of the glacier's tongue (HT) in the basin, total glaciation area S, and the glacial runoff (Q) for the predefined step of air temperature change equal to +0,03°C/year in the Oigaing river basin [23 Tikhanovskaya A.A., Tomashavskaya I.G., 2008] (table 7).
Table 7 - The result of the glaciation parameters and glacial runoff calculation for the Oigaing river basin
Year TS, °C S, km2 HT, km Q, m3/sec
1960 16,9 51,5 3,50 4,27
1980 17,3 47,0 3,54 4,40
2000 17,9 41,3 3,58 4,49
2020 18,5 36,5 3,63 4,51
Glacial runoff remains mostly unchangeable under predefined trend of air temperature that gives evidence of intense melting and intensive consumption of ice storage.
1. Dangerous phenomena associated with the glaciation reduction. Shrinking of glaciation observed the world over, including Central Asian Mountains, leads to the formation of banks of terminal moraines and so-called "dead ice" on the glacier free area. In the summer when seasonal snow and ice cover melts, melt-water accumulates between these banks and forms lakes, those number and size vary from year to year. Such lakes can burst when ice or moraine dams break down, that leads to occurrence of floods and mud flows, often disastrous. This happened for instance in the upper reaches of Shkhimardan river, downstream from Archabashi glacier in the summer of 1998. Similar flood happened in July 1977 in the Isfairansay River basin located to the east from Shakhimardan. There is historical information about other similar floods in Fergana valley [24 Alekseev N.A., 1988, 25 Chub V.E. etc., 2005].
In SANIGMI the catalogue of the lakes, located in the mountains surrounding Uzbekistan territory, was compiled as at 1999-2000 for the assessment of their number and some characteristics (length and width) [26 Murakaev R.R., etc., 2004, 27Glasirin G.E. etc.2005]. There are more that 300 of them. 32 of them are in the Pskem river basin, and 27 are in the Oigaing River basin (left tributary of Pskem located in Uzbekistan). However, inventory is just a first, but important step in such lakes investigation. The information about their size, regime, impounding dams is needed.
It is commonly known, that type of the outburst-hazardous lakes depends on genesis of impounding dams [28 Vinogradov Yu.B., 1977, 29 Costa J.E., 1988, 30 Costa J.E., Schuster R.L., 1988]. There are following types in the mountains of Central Asia:
- the lakes formed as a result of riverbed blocking with landslides or rockfalls from hillsides. For instance, the famous Sarez Lake belongs to this type;
- the glacier-dammed lakes. The well-known Merzbacher lake is the largest in Central Asia. Southern Inylchek glacier serves as a dam for this lake. Other small lakes of this type are met in the glacial basins. Most of them are seasonal.
- moraine-dammed lake are those which are formed on the place of retreating glaciers. Their size generally is not large, but they are widespread.
Lakes of first two types are widely known, as they exist for decades, included into catalogues and mapped. The lakes of the type three are not explored so well. Most of them were formed since last two decades in connection with fast glaciers retreat. At the same time these particular lakes are most dangerous, as the dams impounding them are non-coherent and often has ice core. [31 Dokukin M.D., 1985, 32 Kubrushko S.S., 33 Mavlyudov B.R, 1996].
Apart from these types of lakes, there are lakes formed in the body of the glacier or on its bed. These lakes are not visible; volume of accumulated water is unknown. The floods formed as a result of their burst can lead to the avalanchine mud flows. The best known sample is passage of mudflows along Aksay River, tributary of Alaarcha river (Kyrgyzstan), which occur regularly as a result of fast empting inter- or subglacial of the glacier located in the upper reaches of the river. (Vinogradov Yu. B., 1980]. It turned out that similar cavities of smaller size exist and burst in the Abramov glacier [34 VNII, №1, 1990].
Filling the moraine lakes happens mostly with surface runoff for the account of glaciers and seasonal snow melting, as well as with water incoming by filtration through coarse material of valley slopes and
bottom. Maximum of water level in spring and summer under high air temperature inheres in small mountain dammed and moraine lakes with outflow by filtration through dam body.
Monitoring of the state of moraine lake located before the tongue of Barkrak Middle glacier (№54 [2 Catalogue, 1968]) showed that in the August 2013 area of the lake surface reduced for 37% during a month when weather changes from hot to cold [35 Tikhanovskaya A.A., Tomashevskaya I.G., 2013]. One can conjecture, that sharp increase of the water-surface area will happen under opposite scenario, and in case of extreme precipitation (thunderstorm shower) flow of water over the moraine dam in its lower part can happen, that proves necessity of the glacial lakes monitoring.
Maximum number and maximum areas of the lakes of glacial origin is in the altitude interval 3500-4500 m. By 2003 the number of lakes in this interval became one and a half times as much as in 1987 [36 Nikitin A.M., 1987].
Mechanism of the moraine lakes outburst is not clear yet, however researchers [37 Vinogradov Yu. B., 1980, 33 Mavlyudov B.R. 1996, 38 Golubev G., 39 Nye J.F., 1976, 40 Rothlisberger H., Lang H., 1987] lean towards the view that two following ones are most probable:
- overflow from the lake is absent when volume of water is small; when the water level is high enough, flood channels occurs between lakebed and dam, and lake water rush through and erode the dam;
- at presence of ice kernel inside of dam there is constant insignificant water flow from the lake with low level, and hence water head. In this case, cold flow prevent increasing of channel cross-section by compensating widening of channel as a result of abrasion and melting. When the level and water head become large enough for channel cross-section to surpass its shrinkage for the account of ice flow, water flow starts to increase that can lead to outburst.
Conclusion. Investigation of climate change in Central Asia over the last 50 years showed that in the western periphery of Central Asian mountain system vertical and horizontal gradients of air temperature change in time. In the territory of Central Asia winter air temperature rises much faster than summer one, while precipitation amount remains unchanged or rises slightly. Climate warming led to reduction of glaciation in Central Asia. In particular, glaciers in the Pskem district lost 27% of their area during 19602010. No expected decreasing of glacial part in the annual run off happens in the process of reducing of glaciation area. For the rivers with significant area of glaciation in the headstream, in most of cases impact of glaciation reduction on the glacial part of runoff is not significant and within the limits of annual runoff calculation accuracy on stations located in lower reaches of the rivers. Concerning redistribution of glacial water runoff during the years of different dryness of the year, contribution of ice water into the total river runoff in the summer can reach 20-25% for the dry year and decrease down to 10-12% in a year with intense winter precipitation.
Glaciation reduction is accompanied with increasing of the moraine lakes' number, and level of the mudflow danger is not predicable without additional investigations. Therefore monitoring of periglacial zone is needed, particularly in the regions of remaining rather large, but retreating intensively glaciers with developed moraine cover.
Acknowledgements. Introduced investigation have been carried out in the framework of the project FA-A7-T-118 supported by the State Committee on Science and Technology of the Republic of Uzbekistan and DEFenCC under support of SCOPES Program of Swiss foundation for basic research. Authors express deep appreciation for the support and valuable remarks during preparation of the article to the colleagues from the geographical department of the Moscow State University - O. Tutubalina and D. Petrakov, E. Semakova - senior researcher of the Institute of Astronomy of Academy of Science of the Republic of Uzbekistan, as well as I. Pavlova - UNESCO staff member.
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М. А. Петров1, Г. Е. Глазырин2 , И. Г. Томашевская3, А. А. Тихановская4, Т. Ю. Сабитов5
1 Г.г.-м.к., ага гылыми Rbi3MeTKepi (взбекстан Республикасы мемлекеттiк геология комитетiнiн геология жэне геофизика институты, Ташкент, взбекстан Республикасы) 2 Г.г.д., профессор (взбекстан Республикасы мемлекетлк геология комитетшщ геология жэне геофизика институты, Ташкент, взбекстан Республикасы) 3 К.г.к., ага гылыми кызметкерi (взбекстан Республикасы мемлекеттiк геология комитетшщ геология жэне геофизика институты, Ташкент, взбекстан Республикасы) 4 Ага гылыми кызметкерi (взбекстан Республикасы мемлекетлк геология комитетшщ геология жэне геофизика институты, Ташкент, взбекстан Республикасы) 5 К.г.к., доцент (М. Улугбек атындагы взбекстан ^лттык университет^ Ташкент, взбекстан Республикасы)
ОРТАЛЫЦ АЗИЯ ТАУЛАРЫНДАГЫ ЦАЗ1РП КЛИМАТТЫЩ ЖАГДАЙЛАРДЫЦ М¥ЗДАНУ ЖАГДАЙЫНА, М¥ЗДЫЩ АГЫНЫНА ЖЭНЕ М¥ЗДЬЩ К6ЛДЕРДЩ ЖАРЫЛУЫНА ЭСЕР1
Аннотация. XX гасырдьщ екiншi жартысы мен XXI гасырдьщ бiрiншi онжылдыгындагы Орталык Азияньщ климаттык жагдайлары Орталык Азия тау жуйесшщ батыс шетiндегi квлденец жэне тш температура градиенттерiнiн взгеруiмен сипатталады. Жазгы ауа температурасынын жогарылауы тау муздыктары-нын азаюына экелдг Соцгы 45 жыл iшiнде Гиссар-Алайдыц жекелеген су жинау алаптарындагы м^здыктар шамамен 16%-н, ал Пiскем взеншщ алабындагы мрдыктар 27%-н жогалтты. Мрдыктын азаюы взен режимдерiне, ен алдымен, агыннын жылдык таралуына ыкпал етедг Жауын-шашын аз болган жылдары мрдык агынынын Yлесi 25%-дан асады, ал жауын-шашын квп болтан жылдары ол айтарлыктай твмендейдi. Мрдыктын жойылуынын жатымсыз эсерлерiнiн бiрi - перигляциялык аймакта квлдердiн пайда болуы. Мрдык квлдердщ жагдайына бакылау жYргiзу кажет, себебi олар сел агындарынын каупiн тудыруы мYмкiн.
ТYЙiн свздер: климаттын взгеру^ мрдык агынынын взгеруi, мрдык квлдердщ пайда болуы, Орталык Азиядагы мрдыктардын азаюы.
М. А. Петров1, Г. Е. Глазырин2 , И. Г. Томашевская3, А. А. Тихановская4, Т. Ю. Сабитов5
1 К.г.-м.н., старший научный сотрудник, заведующий центром гляциальной геологии (Институт геологии и геофизики Госкомгеологии РУз, Ташкент, Республика Узбекистан) 2 Д.г.н., профессор (Институт геологии и геофизики Госкомгеологии РУз, Ташкент, Республика Узбекистан) 3 К.г.н., старший научный сотрудник (Институт Геологии и Геофизики Госкомгеологии РУз,
Ташкент, Республика Узбекистан) 4 Старший научный сотрудник, (Институт Геологии и Геофизики Госкомгеологии РУз,
Ташкент, Республика Узбекистан) 5 К.г.н., доцент (Национальный университет РУз им. М. Улугбека, Ташкент, Республика Узбекистан)
ВЛИЯНИЕ СОВРЕМЕННЫХ КЛИМАТИЧЕСКИХ УСЛОВИЙ В ГОРАХ ЦЕНТРАЛЬНОЙ АЗИИ НА СОСТОЯНИЕ ОЛЕДЕНЕНИЯ, ЛЕДНИКОВЫЙ СТОК И ПРОРЫВ ЛЕДНИКОВЫХ ОЗЕР
Аннотация. Климатические условия Центральной Азии во второй половине XX века и в первом десятилетии XXI века характеризуются изменением горизонтальных и вертикальных градиентов температуры на западной периферии Центрально-Азиатской горной системы. Рост летних температур воздуха привел к уменьшению горных оледенений. За последние 45 лет ледники в отдельных водосборных бассейнах Гиссаро-Алая потеряли около 16% площади, в то время как ледники в бассейне реки Пскем - 27% площади. Режимы рек, в первую очередь годовое распределение стока, реагируют на уменьшение ледника. Доля ледникового стока составляет более 25% в годы с небольшим количеством осадков, а в годы с обильными осадками она значительно уменьшается. Одним из негативных последствий схода ледника является образование озер в перигляциальной зоне. Следует следить за состоянием ледниковых озер, поскольку они могут представлять опасность выброса селевых потоков.
Ключевые слова: изменение климата, изменение ледникового стока, образование ледниковых озер, сокращение оледенения в Центральной Азии.
