No abstract

This research is based on multiyear in-situ observations, analysis of satellite and aerial imagery, meteorological data, and mass balance index calculations. Presently, 659 glaciers cover a total area of 322.1 km 2 . We identified four favorable, two neutral, and five unfavorable longer intervals of glacier development since 1940. A decelerating of glacial retreat took place in the 1960s and in the late 1980s/early 1990s. The strong decline in glacial mass between 1995 and 2009 resulted in a fast reduction of the glacial area (0.9% year −1 on the northern slope of Tavan Bogd, 1.5% year −1 at Mongun-Taiga), mostly due to the degradation of small glaciers; after 2009, the glacial loss slowed down. Large valley glaciers behaved asynchronously until recently, when their retreat accelerated rapidly reaching in some cases over 40 m·year −1 . Degradation of the accumulation zone and separation of the debris-covered parts of the glaciers are characteristic for the glacial retreat in the region of research. The time of reaction of the fronts of four valley glaciers of Mongun-Taiga and the northern slope of Tavan Bogd on climatic fluctuations is estimated between 11 and 20 years. Over the next decade, high rates of glacial degradation are expected.

Purpose: The present work focuses on cold alpine soils of the Altai Mountains (Siberia, Russia). Permafrost is widespread and often occurs at a depth of about 100 cm. The area is characterised by extremely cold winters and cool summers: the aim was consequently to find out whether weathering could be more intense on thermally less unfavoured conditions or whether the abundance of water could be a more important factor. Materials and methods: We investigated 10 soils in a very small area close to a local glacier tongue. Five of the investigated soils were south-facing and the other five north-facing. The soils have the same parent material (mica-rich till), altitude, topography and soil age. The vegetation is alpine grassland that is partially intersected with some juniper and mosses. Soil chemical properties such as organic C, N, soil organic matter quality (using DRIFT), pH value, (oxy)hydroxides, total elemental contents (XRF) and soil micromorphology and mineralogy (using diagnostic treatments and XRD) were determined. The age constraint of the site was given by geomorphic studies together with 14C dating of a nearby peat bog and the stable organic matter fraction of the soils. Results and discussion: The soils have a Holocene age. The results showed astonishingly clearly-similarly to the European Alps-that the north-facing soils have a higher weathering state. This is expressed by lower pH values, higher oxalate and dithionite extractable Fe, Al, Mn and Si contents, higher C and N concentrations and stocks when compared to the south-facing sites. No statistically significant differences with respect to weathering indexes could be detected. The geochemical evolution of the soils seems to be enhanced at north-facing sites, even though very severe climatic conditions prevail. Furthermore, biodegradation seems to be less pronounced on north-facing compared to south-facing sites as poorly degraded organic matter is accumulated. This gives rise to more organic ligands that promote metal binding and their subsequent eluviation along the soil profile. Conclusions: We consequently must assume that weathering is not limited by low temperatures in the active layer but is rather controlled by soil moisture that seems to be higher during the warmer period in the north-facing soils. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 -2 - Abstract 27Purpose The present work focuses on cold-alpine soils of the Altai Mountains (Siberia, 28Russia). Permafrost is widespread and often occurs at a depth of about 100 cm. The area is 29 characterised by extremely cold winters and cool summers: the aim was consequently to find 30 out whether weathering could be more intense on thermally less unfavoured conditions or 31 whether the abundance of water could be a more important factor. 32Materials and methods We investigated te...

The Tavan Bogd mountains (of which, the main peak, Khuiten Uul, reaches 4374 m a.s.l.) are situated in the central part of the Altai mountain system, in the territories of Russia, Mongolia and China. The massif is the largest glacierized area of Altai. The purposes of this study were to provide a full description of the scale and structure of the modern glacierized area of the Tavan Bogd massif, to reconstruct the glaciers of the Little Ice Age (LIA), to estimate the extent of the glaciers in 1968, and to determine the main glacial trends, and their causes, from the peak of the LIA. This work was based on the results of long-term field studies and analysis of satellite and aerial data. At the peak of the LIA, Tavan Bogd glaciation comprised 243 glaciers with a total area of 353.4 km2. From interpretation of Corona images, by 1968 the number of glaciers had decreased to 236, with a total area of 242 km2. In 2010, there were 225 glaciers with a total area of 201 km2. Thus, since the peak of the LIA, the glacierized area of the Tavan Bogd mountains decreased by 43%, which is somewhat less than for neighboring glacial centers (i.e., Ikh-Turgen, Tsambagarav, Tsengel-Khairkhan and Mongun-Taiga mountains). The probable causes are higher altitude and the predominance of larger glaciers resistant to warming. Accordingly, the smallest decline in Tavan Bogd occurred in the basins of the Tsagan-Gol (31.7%) and Sangadyr (36.4%) rivers where the largest glaciers are located. In contrast, on the lower periphery of the massif, where small glaciers predominate, the relative reduction was large (74–79%). In terms of general retreat trends, large valley glaciers retreated faster in 1968–1977 and after 2010. During the 1990s, the retreat was slow. After 2010, glacial retreat was rapid. The retreat of glaciers in the last 50–60 years was caused by a trend decrease in precipitation until the mid-1970s, and a sharp warming in the 1990s and early 2000s.

Little is known about the extent of glaciers and dynamics of the landscape in southeastern Russian Altai. The effects of climate-induced fluctuations of the glaciers and the upper treeline of the Mongun-Taiga mountain massif were, therefore, reconstructed on the basis of in-situ, multiannual observations, geomorphic mapping, radiocarbon and surface exposure dating, relative dating (such as Schmidthammer and weathering rind) techniques and palaeoclimate-modelling. During the maximal advance of the glaciers, their area was 26-times larger than now and the equilibrium line of altitude (ELA) was about 800m lower. Assuming that the maximum glacier extent took place during MIS 4, then the average summer temperatures were 2.7℃ cooler than today and the amount of precipitation 2.1 times higher. Buried wood trunks by a glacier gave ages between 60 and 28 cal ka BP and were found 600-700m higher than the present upper treeline. This evidences a distinctly elevated treeline during MIS 3a and c. With a correction for tectonics we reconstructed the summer warming to have been between 2.1 and 3.0℃. During MIS 3c, the glaciated area was reduced to less than 0.5 km² with an increase of the ELA of 310-470m higher than today. Due to higher precipitation, the glaciated area during MIS 3a was close to the current ELA. Exposure dating (¹Be) would indicate that the maximum glacier extension was 24 ka BP, but the results are questionable. From a geomorphic point of view, the maximum extent can more likely be ascribed to the MIS4 stage. We estimate a cooling of summer temperature of-3.8 to-4.2℃ and a decrease in precipitation of 37-46% compared to the present-day situation. Samples of wood having an age of 10.6-6.2 cal ka BP were found about 350m higher than the present treeline. It seems that the summer temperature was 2.0-2.5℃ higher and annual precipitation was double that of the present-day. For that period, the reconstructed glaciation area was 1 km² less than today. Three neoglacial glacier advances were detected. The glaciers covered about double the area during the Little Ice Age (LIA), summer cooling was 1.3℃ with 70% of the present-day precipitation. The reconstructed amplitude of climatic changes and the shift of the altitudinal zones show that the landscape has reacted sensitively to environmental changes and that dramatic changes may occur in the near future.