A shallow ice core re-drilled on the Dunde Ice Cap, western China: recent changes in the Asian high mountains

A 51 m deep ice core was re-drilled on the Dunde Ice Cap of western China in 2002, 15 years after the previous ice core drilling in 1987. Dating by seasonal variations in delta O-18 and particle concentration showed that this 51 m deep ice core covered approximately the last 150 years. The stratigraphy and density showed that more than 90% of the ice core was refrozen ice layers, which comprised less than 5% of the annual accumulation in the older core. This indicates that the ice cap had experienced a more intense melting since 1987, possibly due to climate warming in this region. Mean net accumulation since the last drilling (2002-1987) was 176 mm a(-1), which was considerably smaller than that obtained from the 1987 core (390 mm a(-1), 1987-1963), indicating a significant decrease of net accumulation on the ice cap in the more recent period. The delta O-18 record showed an increasing trend in the late 19th century and the highest in the 1950s, which is consistent with the previous core findings. However, there has been no significant increase in delta O-18 during the last two decades, in contrast to the warming trends suggested by the melt features and other climate records. This discrepancy may be due to the modification of delta O-18 records by melt water runoff, percolation, and refreezing on the ice cap. Results strongly suggest recent significant mass loss of glaciers in the Asian high mountains and serious shortage of water supply for local people in this arid region in the near future.