Assessment of modern glaciological and dimatic indicators in the Mountainous Altai area.pdf Introduction It is widely known that glaciers are the most sensitive indicators of the Earth's climate. Their balance and sizes quickly affect such meteorological characteristics as atmospheric precipitation and the temperature of the air. Monitoring of the Altai glaciers initiated by V.V. Sapozhnikov, B.V. and M.V. Tronov has made it possible to store up extensive data concerning their state and dynamics. Special attention was given to the research of the Aktru mountain and glacier basin where a meteorological station with the standard amount of observations was opened in 1971. Interest in the glacier basin is due to its geographical position in the centre of the Eurasian continent as well as the availability of a long series of direct observations made on the major glaciohydroclimatology parameters which are indicative of the current trends of glaciers dynamics in the acutely continental climatic conditions. From this point of view the Aktru glaciers are regarded as the Siberian basic objects and they are included in the World Glacier Monitoring Network [1-3]. The aim of the current research is to evaluate the meteorological conditions of the mountainous Altai taking into account the present-day climatic trends. Results The article provides a profound analysis of the atmospheric circulation processes, accumulation value, ablation and balance of the Malyi Aktru glacier as well as climatic indicators of temperature regime near the earth's surface above the Altai mountains area. This territory is the so-called fourth-class area determined by means of cluster analysis (spacial classification method) of the average monthly air temperature field (Fig. 1). Fig. 1. Distribution of the air temperature of the classes in the area of the Altai region [4] The quality of the classification favours the view that intra-class distances are 2- 5 times less than inter-class ones. The fourth-class territory includes the most mountainous part of Altai. The Ak-Kem, Aktru, Bertek, Kara-Tureck, Kosh-Agach are located in this area while Ulandryk meteorological station is situated not far from here. This area is characterized by the lowest annual temperatures and the highest intra-class differences (Table 1). These stations are isolated from the impact of warm and humid air masses coming from the Atlantic Ocean. They are located closer to the centre of the Asian anticyclone, which contributes to the forming of severe climate in this area. Table 1. Characteristics of classification of the temperature field in the region class The number of stations Average temperature, °C Variace, °C2 Average correlation coefficient The intraclass distance, °C The interclass distances, °C 2 3 4 1 21 2.5 172 0.99 0.17 0.32 0.25 0.77 2 3 4.0 106 0.99 0.20 0.43 0.88 3 4 0.0 164 0.99 0.20 0.52 4 5 -4.1 153 0.97 0.36 Circulatory processes The meteorological conditions on which the glacier regime is dependent are determined by great circulatory atmospheric processes. In this connection, it is important to reveal the glaciological and climatic effect of the atmospheric circulation relating to the mountainous part of Altai. The atmospheric circulation state is estimated as in the instance of [5] by means of the B.L. Dzerdzeevsky's typing [6]. The elementary circulatory mechanisms (ECM) regularity was estimated according to the ablation and the accumulation periods of the Malyi Aktru glacier. The date of the stable transition at 0 °C average daily temperature of the air in the low glacier boundary was regarded as the conditional limit of accumulation and ablation periods. The end of the ablation period (or the beginning of a new balance year) corresponds to the time of complete covering of a glacier by stable snow cover and a change-over of annual daily temperature of the air to 0 °C in the direction of negative meanings. Warm weather, however, occurs during this period and the following several days, which on the whole, can increase humidity of snow cover in the absence of glacier snowmelt runoff. This snow is the initial stage of winter balance mass glacier formation for the following balance year [1]. As a rule, the beginning of accumulation period (the end of August - the beginning of September) is connected with a series of powerful and intensive snowfalls which result from cyclones coming from the Barents Sea and the Kara Sea as well as the north-west cyclone shifts and formation of high cyclone over the Mountainous Altai [7]. The complete period of the onset of stable negative temperatures of the air is associated with the formation of high pressure area in the form of Asian (Mongol) anticyclone spurs and the penetration of cold Arctic air into the Altai highlands [1, 7]. Overall annual accumulation (ct) and ablation (a) values as well as internal power supply (f lead to annual mass balance (b): b = ct - at + f. Duration of accumulation periods (ct) and the Aktru glaciers snowmelt sufficiently change over the years and depend upon the nature and characteristics of the atmospheric circulation processes. The correlation analysis of the regularity (days) the ECM and constituents of the glacier mass balance (in specific units of g/cm2) showed the most significant relationships. On the basis of the correlation analysis glaciological effective ECM are revealed. They are especially favourable at 5% level: type processes 3, 13w (inverse) and 11a (direct link) refer to ct, at and b with 7as processes (direct and invesre links respectively), 5d (invesre and direct links) shown in Fig. 2. Thus, the high values of с favour 11a subtype processes relating to the northern meridional group and, on the whole, they are prevalent during an accumulation period. Processes of this subtype allow the Siberian anticyclone to occupy almost the entire continent. Gradual circulation of Arctic air south-wards enhances the anticyclone and leads to its stationary state. Cyclonic activity over the oceans is associated with the Arctic front and regeneration of its polar-front cyclones. Cyclonic bursts coming from the South take place along the eastern coast of North America (the Atlantic Ocean) and Asia (the Pacific Ocean). Some cyclones reach the Arctic Ocean (Novaya Zemlya Island and the Kara Sea). ECM 3 and 13w make it possible to reduce accumulation values. During subtype 3 which is characteristic of a warm half a year period, the Mountainous Altai is in the field of high pressure formed by the local conditions. The negative relationship can be accounted for by the fact that this subtype is typical of the warmer periods which are the most common ones in summer, thus, determining the ablation. When ECM 13w occurs, a powerful stationary anticyclone occupying almost the entire Eurasian continent creates a strong blocking to the western flow in the temperate latitudes, thus, preventing precipitation. Processes of 7as subtype are favourable for the intensive glacier ablation. During 7as an active cyclonic activity at the polar front takes place. This ECM also has a high repetition during the ablation period. On the contrary, 5d ECM prevents the thawing processes in summer because it mainly occurs during the colder period with the availability of the stable and extensive winter Siberian anticyclone exhanced by the Arctic influence in the eastern Asian direction [6]. At the same time, 5d process has a positive link while 7as process has a negative connection with the annual balance. Fig. 2. Dynamic ECM schemes: 1 - generalized cyclone trajectories; 2 - the same for anticyclones; 3 - demarcation lines [6] Instrumental (1962-2010) and reconstructed (1900-1961) data on performance characteristics of glaciers Aktru have been used [1-3] for the following circulatory conditions of the dynamics of glacier balance mass constituents are revealed. The period of ct rise from the early of the XXй1 century up to the maximum value 138 g/cm2 in 1921 was characterized by a high regularity of the northern meridional circulation (11a ECM in particular) during the colder periods of the year, having their major maxima in 1917, 1919, 1921. Between 1922 and 1935 the decrease of both characteristics of ct and ECM in a pre-spring period and winter was observed. From 1985 to 1995 the number of days relating to 11a sub-type also increased as well as the glacier balance mass constituents. Annual mass balance of the glacier which is closely associated with amount of the accumulation decreases with the increase of zonal circulation. On the contrary, glacier ablation during summer depends on the activity of zonal flows (ECM 7as). One can observe their overall increase in the first half of the XXth century. During the second half of the period the observed zonal processes weakened. This tendency relating to at values had been observed until 1985. at increase over the last decades is evidently due to the global warming which is accompanied by the southern meridional circulation increase. Warming which began in the mid 1910s has resulted in precipitation increase during the colder period and accumulation values intensity. The links revealed between the changes in the characteristics of the Malyi Aktru glacier mass balance and overall atmospheric circulation make it possible to regard the ECM as good indicators and objective signs of climatic variability of the region concerned. Glaciological and Climatic Indicators The link between glaciation and the climate expressed by the dependence Glaciers = f (climate, topography) can be specified by glaciological and climatic indicators which are better designed for the Aktru basin mountain glacier [8] . Some of the basic glaciological and climatic characteristics are the following: the amount of overage daily above zero air temperatures Ц+0, indicators in the 1° temperature value ablation, duration of ablation period (PA), the annual number of days with snow cover, vertical gradients of meteorological elements, indicator-equivalents (e.g. summer air temperatures decrease by 1°, the increase of solid precipitation) etc. These indicators as climatic ones are widely used in glaciology for balance estimations and they refer to the first type of glaciological and climatic indices. Based on these indicators M.V. Tronov and A.N. Krenke [9] compared them with agroclimatic indices bearing in mind that the conditions of heat and humidity which plants need are also important for glaciers. The difference lies only in the nature of impact (favourable or unfavourable) and the time required for such a manifestation. These indicators relate to the dates of daily average air temperature transition at fixed values (0°C, 10°C), duration periods with positive temperatures, the accumulated amount of positive temperature, hydrothermal coefficient, etc. Our research deals with the thermal regime characteristics (glaciological and climatic parameters) according to the meteorological observations (of daily and monthly resolution) made from 1939 to 2009. The dates of the stable daily transition temperature 0°C (D), the PAI positive temperature duration period, the sum of positive temperatures during the stable transition period at 0 °C (2(+t)y). The sum of positive temperatures from March to November (2(+t)) was also taken into account. Fig. 3. illustrates the dynamics of the regime characteristics of the Malyi Aktru glacier. The climatic parameters are shown in Table 2. On the basis of these results one can state that the PAt longest period is observed at the Kosh-Agach station, while the shortest period is seen at the Kara-Tureck station. The calculation is not statistically provided by the available daily observation amount of data. PAJ amplitude over the area of the district is 48 days which further points to the significant impact of local conditions. Assessment of the trends points to an earlier transition through 0 °C in spring and later to the autumn transition which is reflected in the PAt positive trend. These trends may present part of the cyclical processes which are characteristic of the climatic system. Fig. 3. Time course of the at, ct, b in Malyi Aktru glacier Table 2. Glacioclimatological indicators Rate of change Station(s) (observation period) P D„ STD D. 2(+

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