ISOTOPIC MEASUREMENTS OF PRECIPITATION ON CENTRAL-ASIAN GLACIERS (SOUTHEASTERN TIBET, NORTHERN HIMALAYAS, CENTRAL TIEN-SHAN)

The glacial regions of central Asia considered in our study are influe nced by tropical monsoons and western extratropical cyclones. Isotopic delta(18)O and delta D data were obtained over 3 years in three clima tic regions: Gongga massif of southeastern Tibet (windward slope of su mmer monsoon), Xixibangma massif on the northern slope of the Himalaya s (leeward of summer monsoon), and the massifs of Pobeda-Khan Tengry i n the central Tien Shan (exposed to western airstreams). The survey re ported here provides information from atmospheric precipitation, snow pits and a 23 m ice core. The significant differences of oxygen isotop ic ratios (from -25.1 per mil to -9.5 per mil) indicate that the India n and Pacific Oceans as well as the Atlantic Ocean ate sources of mois ture on the northern slope of the Himalayas and southeastern Tibet. Sh arply changing isotopic ratios in precipitation corresponded to changi ng wind direction and were associated with different sources of air ma sses on the northern slope of the Himalayas and southeastern Tibet. St eady isotopic ratios in atmospheric precipitation and the absence of c hanging delta(18)O composition in a 23 m ice core suggest only one sou rce of moisture in central Tien Shan. The relatively heavier oxygen is otopic ratios in atmospheric precipitation and ice core indicate the m oisture from which the precipitation was derived originated over the C aspian or Mediterranean seas. Within the Eurasian continent, air masse s developed over the Atlantic Ocean advance farther than those from th e Pacific and Indian Oceans.