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Figure 15. Relationship between the average area of the glaciers in different river basins of Tavan Bogd at the LIA peak and glacial reduction (%) between the LIA peak and 2010. 2. The aspect of the slopes had little effect on the degree of glacier shrinkage. At the same time, there is a clear negative correlation between the size of the glaciers and the rate of degradation, evidenced by the glaciers of the relatively low-altitude periphery of Tavan Bogd, which have decreased to the greatest extent. This is clearly seen in the example of the relationship between the average area of glaciers in river basins in the Tavan Bogd area in the LIA and the proportional reduction of their area (Figure 15).

Figure 15 Relationship between the average area of the glaciers in different river basins of Tavan Bogd at the LIA peak and glacial reduction (%) between the LIA peak and 2010. 2. The aspect of the slopes had little effect on the degree of glacier shrinkage. At the same time, there is a clear negative correlation between the size of the glaciers and the rate of degradation, evidenced by the glaciers of the relatively low-altitude periphery of Tavan Bogd, which have decreased to the greatest extent. This is clearly seen in the example of the relationship between the average area of glaciers in river basins in the Tavan Bogd area in the LIA and the proportional reduction of their area (Figure 15).

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Figure 1. Geographical location of the Tavan Bogd mountain range.
Figure 1. Geographical location of the Tavan Bogd mountain range.
Table 1. Satellite and aerial imagery used in the study of Tavan Bogd glaciers. Every scene was radiometrically normalized and geographically referenced using orbital parameters. The automatic and systematic geometric correction of raster data was applied, based on a mathematical model of the view angles of the satellite camera and its position at the moment of the image collection (i.e., a rigorous model). UTM/WGS 84 projection (zone 46) was identified as the reference frame for georeferencing. The imagery has been orthorectified using 30 m SRTM 1 Arc-Second Global (DEM) downloaded from the USGS EROS Data Center [62] and treated with a moderate-sharpening filter for graphic quality preservation. All aerial photographs were also geographically referenced using ground control points (GCP
Table 1. Satellite and aerial imagery used in the study of Tavan Bogd glaciers. Every scene was radiometrically normalized and geographically referenced using orbital parameters. The automatic and systematic geometric correction of raster data was applied, based on a mathematical model of the view angles of the satellite camera and its position at the moment of the image collection (i.e., a rigorous model). UTM/WGS 84 projection (zone 46) was identified as the reference frame for georeferencing. The imagery has been orthorectified using 30 m SRTM 1 Arc-Second Global (DEM) downloaded from the USGS EROS Data Center [62] and treated with a moderate-sharpening filter for graphic quality preservation. All aerial photographs were also geographically referenced using ground control points (GCP
Figure 2. Delineation of the Little Ice Age (LIA) moraine, Postigiyn-Gol basin, using a Geoeye-1 image. feature is the presence of the ice core of glacial origin. Starting in the late 1990s, an intensification of thermokarst processes on the LIA moraines has given rise to numerous thermokarst depressions, thermoerosional forms and landslides [6], which stand out in steep areas of dumped moraines in the form of sharp and contrasting dark bands visible in images with a resolution better than 15 m.
Figure 2. Delineation of the Little Ice Age (LIA) moraine, Postigiyn-Gol basin, using a Geoeye-1 image. feature is the presence of the ice core of glacial origin. Starting in the late 1990s, an intensification of thermokarst processes on the LIA moraines has given rise to numerous thermokarst depressions, thermoerosional forms and landslides [6], which stand out in steep areas of dumped moraines in the form of sharp and contrasting dark bands visible in images with a resolution better than 15 m.
Table 2. Glacier inventory of Tavan Bogd for 2010.
Table 2. Glacier inventory of Tavan Bogd for 2010.
L—maximal length, km; H1—the lowest point altitude, m; H2—the highest point altitude, m; M—morphologic type; S—area, km; ELA—average equilibrium line altitude, m; a—average slope angle, m; Al—average accumulation zone azimuth, °; A2—average ablation zone azimuth, °. Indices A, B after the same number of glaciers mean different slope aspects of parts of flat summit glaciers. Table 2. Cont.
L—maximal length, km; H1—the lowest point altitude, m; H2—the highest point altitude, m; M—morphologic type; S—area, km; ELA—average equilibrium line altitude, m; a—average slope angle, m; Al—average accumulation zone azimuth, °; A2—average ablation zone azimuth, °. Indices A, B after the same number of glaciers mean different slope aspects of parts of flat summit glaciers. Table 2. Cont.
Figure 3. Glacial areas (river basins) of Tavan Bogd. 1—Kalguty, 2—Ak-Alaha, 3—Sangadyr, 4—Budiuhanasthe, 5—Postgiyn-Gol, 6—Arshan-Gol, 7—Mogotiyn-Gol, 8—Ikh-Hatugiyn-Gol, 9—Baga-Hatugiyn, 10—Nalia-Gol, 11—Tsagan-Gol, 12—Ikh-Oigoryn-Gol, 13—Shepk-Oygoryn-Gol.
Figure 3. Glacial areas (river basins) of Tavan Bogd. 1—Kalguty, 2—Ak-Alaha, 3—Sangadyr, 4—Budiuhanasthe, 5—Postgiyn-Gol, 6—Arshan-Gol, 7—Mogotiyn-Gol, 8—Ikh-Hatugiyn-Gol, 9—Baga-Hatugiyn, 10—Nalia-Gol, 11—Tsagan-Gol, 12—Ikh-Oigoryn-Gol, 13—Shepk-Oygoryn-Gol.
Figure 4. Distribution of the quantity and total area of glaciers in different intervals of areas.
Figure 4. Distribution of the quantity and total area of glaciers in different intervals of areas.
Figure 5. Distribution of the number of glaciers in 2010 by morphological types
Figure 5. Distribution of the number of glaciers in 2010 by morphological types
Figure 6. Distribution of glacial area in 2010 by morphological types.
Figure 6. Distribution of glacial area in 2010 by morphological types.
Figure 7. The aspect distribution of the number and area of glaciers in 2010. Nevertheless, the aspect distribution of glacial area (Figure 7) is more complex, with several peaks in the north-western, north-north-eastern, east-north-eastern (main) and southeastern (the least pronounced). Such a distribution, obviously, is determined by the complex geomorphological configuration of Tavan Bogd mountain massif, with varying lengths and heights of the slopes of different orientations.
Figure 7. The aspect distribution of the number and area of glaciers in 2010. Nevertheless, the aspect distribution of glacial area (Figure 7) is more complex, with several peaks in the north-western, north-north-eastern, east-north-eastern (main) and southeastern (the least pronounced). Such a distribution, obviously, is determined by the complex geomorphological configuration of Tavan Bogd mountain massif, with varying lengths and heights of the slopes of different orientations.
$3500—area with altitudes over 3500 m a.s.l. Table 3. Glacio-geomorphologic features of different river basins of Tavan-Bogd.
$3500—area with altitudes over 3500 m a.s.l. Table 3. Glacio-geomorphologic features of different river basins of Tavan-Bogd.
Figure 8. Distribution of the quantity and total area of glaciers at the peak of the LIA in different intervals of areas.
Figure 8. Distribution of the quantity and total area of glaciers at the peak of the LIA in different intervals of areas.
Figure 9. The aspect distribution of the number and area of glaciers at the peak of the LIA. The morphology of the glaciers in the LIA maximum did not differ much from the current morphology. Valley and flat top glaciers constituted a somewhat larger proportion of the total quantity and total area of the glaciers (5% difference for the valley glaciers, for both quantity and area), which reflects the greater development of large glacial forms (Figures 10 and 11). After the LIA, some valley glaciers divided into smaller glaciers of other morphological types or simply transformed into cirque-valley glaciers.
Figure 9. The aspect distribution of the number and area of glaciers at the peak of the LIA. The morphology of the glaciers in the LIA maximum did not differ much from the current morphology. Valley and flat top glaciers constituted a somewhat larger proportion of the total quantity and total area of the glaciers (5% difference for the valley glaciers, for both quantity and area), which reflects the greater development of large glacial forms (Figures 10 and 11). After the LIA, some valley glaciers divided into smaller glaciers of other morphological types or simply transformed into cirque-valley glaciers.
Figure 10. Distribution of the number of glaciers at the peak of the LIA by morphological types.
Figure 10. Distribution of the number of glaciers at the peak of the LIA by morphological types.
Figure 11. Distribution of glacial areas in the LIA by morphological types.
Figure 11. Distribution of glacial areas in the LIA by morphological types.
Table 4. Glacial shrinkage in different river basins after the LIA peak.
Table 4. Glacial shrinkage in different river basins after the LIA peak.
Figure 12. Glacial shrinkage after the LIA peak in the north-east of Tavan Bogd. In the north-eastern periphery of Tavan Bogd, large glaciers were absent even at the time of the LIA peak (Figure 12). Glacial recession here was mostly expressed by the disappearance of small hanging and cirque glaciers (31 after the LIA peak). If the rates of glacial retreat that took place in 1968-2010 continue into the future, the glaciers here will disappear completely by 2060.
Figure 12. Glacial shrinkage after the LIA peak in the north-east of Tavan Bogd. In the north-eastern periphery of Tavan Bogd, large glaciers were absent even at the time of the LIA peak (Figure 12). Glacial recession here was mostly expressed by the disappearance of small hanging and cirque glaciers (31 after the LIA peak). If the rates of glacial retreat that took place in 1968-2010 continue into the future, the glaciers here will disappear completely by 2060.
@ Paleo reconstructions and aerial images analysis, > aerial and satellite images analysis, © satellite images analysis, 4 analysis of satellite images and in situ observations of other authors [38], © analysis of satellite images and in situ observations, ‘ in situ observations. Table 5. Recession of the glaciers of the north slope of Tavan Bogd.
@ Paleo reconstructions and aerial images analysis, > aerial and satellite images analysis, © satellite images analysis, 4 analysis of satellite images and in situ observations of other authors [38], © analysis of satellite images and in situ observations, ‘ in situ observations. Table 5. Recession of the glaciers of the north slope of Tavan Bogd.
Figure 13. Glacial shrinkage after the LIA maximum in the central part of Tavan Bogd.
Figure 13. Glacial shrinkage after the LIA maximum in the central part of Tavan Bogd.
@ Paleo reconstructions and aerial images analysis, ° aerial and satellite images analysis, © satellite images analysis, 4 satellite images analysis and in situ observations of other authors [35], © satellite images and in situ observations analysis, f in situ observations, ® in situ observations of other authors [31] and paleo reconstructions, © in situ observations of other authors [31,32,35]. Table 6. Rates of retreat of Kanas (Halasi, Przewalski, No. 46, Figure 13) glacier. acier lost four large tributaries, the total area of Kanas glacial system decreased to 47.5 km? (a decline 29%), the glacial terminus was 3.1 km shorter, and its lowest point was 250 m higher. The patterr ‘retreat of Kanas glacial terminus (Table 6) is li ke the one revealed for the glaciers of the northerr ope: rapid retreat in 1968-1989, slower retreat in the 1990s, and an abrupt acceleration after 2006 celerating to extremely high rates in 2010-20 8. Also, a longer range of observations gave the portunity to reveal a generally slow retreat in 1820-1909, fast retreat in 1909-1916, and a slowdowr 1959-1968. In recent years, rapid glacial retrea acier and the loss of further tributaries, primari is a sign of the further disintegration of the Kanas y the lower south-western ones.
@ Paleo reconstructions and aerial images analysis, ° aerial and satellite images analysis, © satellite images analysis, 4 satellite images analysis and in situ observations of other authors [35], © satellite images and in situ observations analysis, f in situ observations, ® in situ observations of other authors [31] and paleo reconstructions, © in situ observations of other authors [31,32,35]. Table 6. Rates of retreat of Kanas (Halasi, Przewalski, No. 46, Figure 13) glacier. acier lost four large tributaries, the total area of Kanas glacial system decreased to 47.5 km? (a decline 29%), the glacial terminus was 3.1 km shorter, and its lowest point was 250 m higher. The patterr ‘retreat of Kanas glacial terminus (Table 6) is li ke the one revealed for the glaciers of the northerr ope: rapid retreat in 1968-1989, slower retreat in the 1990s, and an abrupt acceleration after 2006 celerating to extremely high rates in 2010-20 8. Also, a longer range of observations gave the portunity to reveal a generally slow retreat in 1820-1909, fast retreat in 1909-1916, and a slowdowr 1959-1968. In recent years, rapid glacial retrea acier and the loss of further tributaries, primari is a sign of the further disintegration of the Kanas y the lower south-western ones.
@ Paleo reconstructions and aerial images analysis [40], > aerial and satellite images analysis, © satellite images analysis, ¢ satellite images analysis and in situ observations of other authors, © satellite images and in situ observations analysis, f in situ observations, & in situ observations of other authors and paleo reconstructions, © in situ observations of other authors. Table 7. Rates of retreat of Alexandra (No. 203) and Potanin (No. 205) glaciers.
@ Paleo reconstructions and aerial images analysis [40], > aerial and satellite images analysis, © satellite images analysis, ¢ satellite images analysis and in situ observations of other authors, © satellite images and in situ observations analysis, f in situ observations, & in situ observations of other authors and paleo reconstructions, © in situ observations of other authors. Table 7. Rates of retreat of Alexandra (No. 203) and Potanin (No. 205) glaciers.
Figure 14. Glacial shrinkage after the LIA maximum in the south-east of Tavan Bogd. In the southeastern periphery of the massif (Figure 14), the glaciers from the LIA peak hav lost from 53 to 79% of their area. Disintegration of valley and cirque-valley glaciers has led to th present-day dominance of small hanging and cirque glaciers in this part of Tavan Bogd.
Figure 14. Glacial shrinkage after the LIA maximum in the south-east of Tavan Bogd. In the southeastern periphery of the massif (Figure 14), the glaciers from the LIA peak hav lost from 53 to 79% of their area. Disintegration of valley and cirque-valley glaciers has led to th present-day dominance of small hanging and cirque glaciers in this part of Tavan Bogd.
Figure 16. Changes of average summer temperature (relative to multiyear average) for three meteorologic stations of Altai and 5-year moving average curves.
Figure 16. Changes of average summer temperature (relative to multiyear average) for three meteorologic stations of Altai and 5-year moving average curves.
Table 8. Estimation of glacierized area of Tavan Bogd by different authors.
Table 8. Estimation of glacierized area of Tavan Bogd by different authors.
Figure 17. Changes of annual precipitation (relative to multiyear average) for three meteorological stations of Altai and 5-year moving average curves. 5. Discussion
Figure 17. Changes of annual precipitation (relative to multiyear average) for three meteorological stations of Altai and 5-year moving average curves. 5. Discussion
Figure 18. Comparison of the contours of glaciers in the basin of the Sangadyr river, obtained by us, with the contours from the “Second Glacier Inventory of China”. Upper left corner—a fragment of SPOT 5 satellite image (2010).
Figure 18. Comparison of the contours of glaciers in the basin of the Sangadyr river, obtained by us, with the contours from the “Second Glacier Inventory of China”. Upper left corner—a fragment of SPOT 5 satellite image (2010).
Remarks: A S (%)—changes of glacial area from the LIA. Other symbols see in Table 2. Table 9. Reconstructed LIA glazierisation of different glacial centers and their changes till present (2002-2013) [27].
Remarks: A S (%)—changes of glacial area from the LIA. Other symbols see in Table 2. Table 9. Reconstructed LIA glazierisation of different glacial centers and their changes till present (2002-2013) [27].
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