Climatic records in a firn core from an Alpine temperate glacier on Mt. Yulong, southeastern part of the Tibetan Plateau

Mr. Yulong is the southernmost glacier-covered area in Eurasia, including C hina. There are 19 sub-tropical temperate glaciers on the mountain, control led by the southwestern monsoon climate. In the summer of 1999, a firm core , 10.10 m long, extending down to glacier ice, was recovered in the accumul ation area of the largest glacier Baishui No. 1. Periodic variations of cli matic signals above 7.8 m depth were apparent, and net accumulation of four years was identified bq the annual oscillations of isotopic and ionic comp osition. The boundaries of annual accumulation were confirmed by higher val ues of electrical conductivity, and pH, and bq dirty refreezing ice layers at the levels of summer surfaces. Calculated mean annual net accumulation f rom 1994/1995 to 1997/1998 tt,ns about 900 mm water equivalent. The amplitu de of isotopic variations in the profile decreased with increasing depth, a nd isotopic homogenization occurred below 7.8 m as a result of meltwater pe rcolation. Variations of delta O-18 above 7.8 m showed an approximate corre lation with the winter climatic trend at Lijiang station, 25 km away. Conce ntrations of Ca2+ and Mg2+ were much higher than those of Na+ and K+, indic ating that the air masses for precipitation were mainly from a continental source, and that the core material accumulated during the winter period. Th e close correspondence of Cl- and Na+ indicated their common origin. Very l ow concentrations of SO42- and NO3- suggest that pollution caused by human activities is guile low in the area, The mean annual net accumulation in th e core and the estimated ablation indicate that the average annual precipit ation above the glacier's equilibrium line is 2400-3150 mm, but this needs to be confirmed by long-term observation of mass balance.