藏南冰前湖枪勇错近百年沉积速率变化及冰川进退反演

Continental glaciers on the Tibetan Plateau are sensitive to regional and global climate change. Since the industrial revolution, with the acceleration of global warming (especially in the Northern Hemisphere), glaciers in most parts of the Tibetan Plateau have shrunk significantly over the past century. The sediments in proglacial lakes are one of the direct record carriers of glacial fluctuations, but little is known about how their sedimentation rate (SR) responds to glacier and climate changes, particularly under the background of global warming. In this study, the ²¹⁰Pb and ¹³⁷Cs activities were used to constrain the age of a core (QY5) from Qiangyong Co in southern Tibet and to calculate the SRs of the core sediments at different depths. By comparing the SRs of the core (QY5) with those of the QY-3 core from central Qiangyong Co, the history of glacial fluctuations and its relationship with air temperature during the last century were revealed. The results show that the average SR of upstream of Qiangyong Co (QY5) is 0.21 cm/a, about double of the centre of the lake (QY-3), but with the same patterns. High SRs are corresponded to warm temperatures, as a direct response to the glacial retreat within the Qiangyong catchment: (1) from 1900s to 1960s, the SR of Qiangyong Co increased and fluctuated greatly as a result of the glacial retreat, corresponding to increased temperature in Tibet between 1890s and 1950s; (2) during 1960s-1985 when temperature decreased, the SR was low and stable, indicating stable Qiangyong glacier; (3) since 1985, the SR in Qiangyong Co increased gradually, as a direct response to glacier retreat under the acceleration of the global warming. Over a short time scale, the change of the Qiangyong glacier revealed by the SR in the proglacial lake is mainly controlled by air temperature, rather than by precipitation. However, there is a 5 to 10 years delay of glacier retreat to increased temperature. Due to global warming and the delayed response of glacier retreat to temperature, the melting rate of the Qiangyong glacier may accelerate in the next decades, and the Asian water tower will face a new challenge.