气候变化领域集成服务门户

delta O-18 measurements based on systematic sampling and isotopic modeling have been adopted to study the controls of stable isotopes in lake water in two lake basins (lakes Yamdrok-tso and Puma Yum-tso) at two different elevations on the southern Tibetan Plateau. Temporally, delta O-18 values in precipitation and lake water display a seasonal fluctuation in both lakes. Spatially, delta O-18 values in the two lake basins increase by 10 parts per thousand from the termini of glaciers to the lake shores, by similar to 1 parts per thousand from the lake shores to the lake center and by 0.4 parts per thousand from the water surface to depth in these lakes. The clear annual delta O-18 variations indicate that lake water mixes sufficiently in a short time. Model results show that glacial meltwater and surface lake-water temperature are not the dominant factors in the balance process of stable isotopes in lake water. Equilibrium delta O-18 values decrease by 0.8 parts per thousand for Yamdrok-tso lake and 0.6 parts per thousand for Puma Yum-tso lake when glacial meltwater contributions to these lakes shrink by 60%. delta O-18 ratios increase rapidly during the initial stages and take a longer time to approach the equilibrium value.