Current state and changes of glaciers in the Tavan Bogd Mountains (Mongolia)

Abstract

This study is the first stage of detailed investigation of large glaciers located in the Tavan-Bogd Mountains. The main task of this work is to estimate a current state and dynamics of glaciers and to update glacier and rock-glacier inventory. Basing on results of 2013 field survey together with remote sensing data the main glaciers located on eastern slopes of the Tavan Bogd mountain massif in the Tsagan-Us and Tsagan-Gol river basins are described (these glaciers are Potanin, Alexandra, Grane, Kozlov, and Krylov ones). In order to monitor regime of glacier systems the geodetic survey of glaciers and rock-glacier edges was carried out using Trimble GNSS system and the ranging mark system. The Landsat satellite images made taken in August-September of 1989, 2006, and 2013, their spatial resolution 15-30 m, were used to map areas of debris-free glaciers and to estimate the glacier changes between 1989 and 2013. Pictures were taken from the USGS site, the ArcGIS software was used for this work. In addition, the high-resolution satellite pictures with resolution of 0.5–2.5 m made at the end of the ablation season if 2008 (CARTOSAT-1) and 2010 (Geoeye-1 and SPOT-5) were also used to analyze current conditions and changes of the above glaciers and to improve visual estimation of the Landsat imagery. In 2013, the study included 26 glaciers with the debris-free glacier area of 67 km 2 in the Tsagan-Gol river basin and 37 glaciers with area of 30 km 2 in the Tsagan-Us river basin. According to our estimates, areas of these glaciers did not significantly changed since 1989 however a certain regression of the glacier tongues had been fixed. The Kozlov glacier retreated with average rate of 21 m/year between 2001 and 2013. Retreat of the Potanin glacier was slower and between 1989 and 2001 the average rate was equal to 5 m/year, but between 2001 and 2013 it became more active and its average rate reached 24 m/year. One of the largest One of the largest rock-glacier of the Tavan Bogd Mountains was found in the Tsagan-Us valley on its south-eastern slope, its area was estimated 1.2 km 2 , length – 3 km, steep front height – 20–25 m. Indirect indicators of its activity such as transverse and longitudinal furrows were noticed. Using data of local weather station data we calculated some climatic characteristics needed to monitor equilibrium line for end of the 2013 ablation season. Mean summer temperature on the weighted mean equilibrium line of five glaciers (3250 m a.s.l.) was defined as 1.0 °С. Ablation–accumulation value was estimated 110 g/cm 2 and the mean annual snowfall on the equilibrium line as 785 mm.