Monsoon and dust signals recorded in Dasuopu glacier, Tibetan Plateau

Abstract

During summer 1997, a 15 m firn core was recovered from Dasuopu glacier (28°23' N, 85°44' E; 7000 m a.s.l.) on the northwest margin of Xixabangma Feng in the central Himalaya. Oxygen isotope values and concentrations of Ca2+, Mg2+, NH4+, SO42- and NO3- were measured over the 10 years of snow accumulation captured in the firn core. The seasonal variations of δ18O values and major-ion concentrations in the Dasuopu core indicate that summer monsoon and dust signals are clearly recorded in Dasuopu glacier. Annual variations in δ18O values are controlled by the amount effect, with more negative (i.e. lighter) δ18O values representing summer monsoon precipitation characteristic of tropical regions. Higher concentrations of Ca2+, Mg2+ and SO42- reflect the influx of mineral aerosols from the vast arid and semi-arid desert regions to the north and west during the spring dust-storm period. High spring concentrations of NH4+ and NO3- appear to reflect changes in regional biogenic-source strength.