Summer monsoon and dust signals recorded in the Dasuopu firn core, central Himalayas

Abstract

In September 1997, a 15-m firn core was recovered from an elevation of 7 000 m a. s. I, from the Dasuopu Glacier in the central Himalayas. The analysis of 6Is0 values and major ion ( Ca2 + , Mg2 + , NH,' , SO:- and NO, ) concentrations shows that average annual accumu- lation is 0.75 m (water equivalent) in the Dasuopu firn core. The seasonal variations of 6180 values and major ion concentrations in the core indicate that present summer monsoon and dust signals are recorded with high-resolution in the Dasuopu Glacier. 6180 in precipitation are con- trolled by amount effect in summer monsoon season, more negative 6180 is representative of summer monsoon signal in snow layers. Higher concentrations of Ca2 + , Mg2 + , SO: - and NO; are dominated by spring dust storm imput derived from the arid and semi-arid desert regions in central Asia. Also EOF analysis verifies that high spring concentrations of major ions are consis- tent. Due to the possibly different sources, the secondary variations of NH,' and NO, are neg- atively relevant with that of Ca2+ and Mg2 + . CAUSED by the variations of summer monsoon strength and arid and semi-arid environment, the change of precipitation in monsoon area and atmospheric dust is closed to human being life. Ice core records with high-resolution may provide luxuriant infonnation about the monsoon and dust change. Due to its high el- evation, the Himalayas acts as a boundary between the Indian summer monsoon region to the south and the cold and arid Qinghai-Tibetan Plateau controlled by continental climate to the north, and therefore ice core records from such sites can provide insight into the change of summer monsoon and atmospheric envi- ronment.