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Past and Prospective Change in State of Central Asian Glaciers

Congress: 2008
Author(s):

Keyword(s): Central Asia, long term glaciers fluctuation, extreme and average glaciers runoff
Article: Poster:
AbstractData on long term change of glaciers size are necessary for modeling and forecasts water resources in numerous river basins located in the High Asia Mountain Regions like Tien-Shan, Pamir, Hindu Kush, Kunlun, Himalaya, etc. Total area of glacier and its morphological components (accumulation and ablation fields, bare ice and moraine cover) are main characteristics for hydrological computations and analyzing relationship between climate change and fluctuation of glaciers size. Knowledge on temporal variability of glaciers area at regional scale is rather poor and restricted. For example, in the Aral Sea Basin such data are available in general for one-two temporal cuts only during end of 50-ies and 1980. Large gap of information for the considered area is filled by author for upstream of Amudarya river basin both computational methods and processing remote sensing images of Pamir and Hindu Kush mountain areas obtained at 2000-2001 from LANDSAT 7 ETM+ and TERRA satellites. Amudarya is largest river in the Aral Sea Basin which provides 64.3% of total runoff in the region. The paper presents information on change Central Asian glaciers area on four temporal cuts during 1961- 2000 years. Future state of glaciers is also projected by 2020. Scientific background which was used to get these data consists of several independent components. (a) Adjusting of glaciers area values to the selected unified terms. It was done by simple linear interpolation or extrapolation when we had at least two estimations of area. (b) Determination glaciers area F outside of known empirical temporal range. Firstly it could be done by linear extrapolation and secondly by means of equations: Fi+1=Fi-dF/dT×T, dF/dt=f(IAc,IAb) or dF/dt=f(TS), where T is time interval, IAc and IAb are indexes of yearly accumulation and ablation. Instead of IAc was used sum of precipitation for characteristic season and instead of IAb - mean summer air temperature TS. (c) Recognition and digitizing glacier contours on remote sensing images and processing sets of such contours by means of known GIS software. Finally the following conclusions were obtained. 1. Data on long term variability of glaciers area during 1961-2000 should be considered as rather reliable because percentage of results based on using large scale maps, air-photo survey, and remote sensing images for monitoring glaciers change equaled by years: 1961 – 100%, 1980 – 66%, 2000 – 74%. 2. Data on glaciers shrinkage coordinate well with other known similar information in mountain regions of Asia and Europe. 3. Extreme and average contributions of total melting volumes in glaciers area to the annual and seasonal runoff in the Aral Sea Basin stress vital role of glaciers water resources there. 4. Projected value of glaciers area by 2020 was obtained by linear extrapolation of dF/dt during 1991-2000 and it turned out larger in comparison the same one but after using trend equation for 1961-2000 years. 5. Statistical distribution of total melting values is essentially asymmetrical and differs from binomial curve at Cs=2Cv.
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