Research On Ice Core Dating Of Urumqi Glacier No.1in Eastern Tianshan Mountains, China

Glaciers ice core records the environmental informatio n of the history. Ice corehas its high resolution, information, the true, long time series and cleanliness, andbecome important in reconstructing ancient climate and environment change andmonitoring the modern climate and environment change etc. Glacier ice core, recordsthe historical period of the climate information environment. A suite of ice cores（T₀-T₃） were recovered from1991to1998at Urumqi Glacier No.1in easternTianshan Mountains, China, which are in the arid and semi-arid region in Central Asia,to explore the environmental information in the historical period in this area.This paper study mainly ice core T₂（80.1m） drilled in May1996by several icecore dating methods, to reveal climate change at the headwater of Urumqi in recentcenturies, The result was showed as following:（1） As basic knowledge for the ice core dating, annual net accumulation （28.4cmieq） was determined by identifying overlaps in chemical profiles of two ice coresdrilled in different year, which is higher than on site mass balance budget, suggestinga potion of ice mass came from higher reaches of the glacier through ice flow.（2） The study of formation process of light stable isotopic ratio and dust layer inthe ice core during the past several years made a great contribution to the ice coredating. This paper presents chronology establishment process of T₂（80.1m）. Crosscounting of seasonal variations in chemical species profiles was employed for datingthe top32m section. By comparing δ¹⁸O and Mg²⁺ profiles to temperature recordreconstructed from tree rings, obtained were dating results in lower part of the core（33m-77.25m）, which presents the age-depth relationship for the entire core,meanwhile, vertical formation velocity of visible dust horizons at drilling site leads toanother age-depth equation. The result indicates that T₂contained658years.