HR: 1340h
AN: A13B-0109    [Abstracts]
TI: Permafrost Degradation in the Tien Shan Mountains, Central Asia
AU: * Marchenko, S
EM: ffssm1@uaf.edu
AF: Geophysical Institute, UAF, POB 757320, Fairbanks, AK 99775 United States
AU: Gorbunov, A
EM: permafrost@nets.kz
AF: Permafrost Institute, RAS, POB 310, Almaty, 480000 Kazakhstan
AU: Romanovsky, V
EM: ffver@uaf.edu
AF: Geophysical Institute, UAF, POB 757320, Fairbanks, AK 99775 United States
AB: The climatic processes during the 20th century and especially during the last three decades have a significant impact on the thermal state of mountain permafrost. Geothermal observations in the Tien Shan Mountains indicate that during the last 30 years permafrost temperatures have increased by 0.2-$0.3\deg$C for undisturbed sites, and up to $0.6\deg$C of those affected by human activities. In the Northern Tien Shan, the average active layer thickness increased by 26% in comparison with the early 1970s. At the same time, most glaciers in Central Asia have a substantial loss of their masses. The glaciated area of the Zailiysky Alatau (Northern Tien Shan) has been reduced by 29.2% during 1955-90 (Vilesov and Uvarov, 2001). Mountain permafrost and associated periglacial landforms contain large quantities of stored ground ice. The moraines, rock glaciers and other coarse blocky material have especially high ice content (40-90% by volume). Coarse blocky debris of various origins is widespread in the Tien Shan and occupies a large area of high-mountain territory. Convective mass and heat transfer, especially during the cold period, are very typical for the blocky material because of its high porosity. The mean annual temperatures inside coarse debris are typically 2.5-$4.0\deg$¥ colder than the mean annual air temperatures. Melted and condensed water penetrates into coarse debris, then freezes and cements the debris. The result is an ice-block mass with high ice content up to 50% by volume. The approximate evaluation shows that the quantity of water stored as ground ice in the Tien Shan is comparable with the volume of modern glaciers in the region. The total volume of surface ice over the Tien Shan Mountains is about 423 km$^{3}$ (Vilesov and Belova, 1989). The estimated ground ice volume is about 320 km$^{3}$ (Gorbunov and Ermolin, 1981). Under continuing warming and recession of glaciers in Central Asia, the ground ice could increase future water supply, and the melt waters from permafrost could become an increasingly important source of fresh water in this region in the near future. Gorbunov, A. and Ermolin, E. 1981. Ground Ice of Central Asian Mountains. Glac. Studies, Moscow, 41:59-62 (in Russ.). Vilesov, E. and Uvarov, V. 2001. The evolution of modern glaciation of the Zailiysky Alatau in the 20th century. Almaty, 252 p. (in Russ.). Vilesov, E. and Belova, I. 1989. Reserves of ice and general features of modern glaciation of the Tien Shan. Geocryological Research in the Mountains of USSR, Yakutsk, 117-130 (in Russ).
DE: 1655 Water cycles (1836)
DE: 1823 Frozen ground
DE: 1620 Climate dynamics (3309)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting