Recent periglacial debris flows driven by climatic warming in the southeastern Tibet

Glacier retreat and snow melting promote periglacial debris-flow occurrence in the Tibetan Plateau and surrounding mountains. We collect data of 32 historical events in the Zelunglung, Xueka, Tianmo catchments of the southeastern Tibet by retrospective analysis and on-site investigations. It is found that sedimentation on the Zelunglung debris flow fan reduces to pre-earthquake level about 40 years after the 1950 Assam Earthquake. In recent decades, debris flow occurrence lags behind the average annual temperature/summer temperature peaks by 2 to 3 years, indicating that the debris flows have shifted from being earthquake-driven to climate-warming-driven. 11 historical runoff-generated debris flow events were identified from 1940 to the present using dendrochronological analysis at the Xueka catchment, indicating the positive feedback between debris flow and climate warming. Large-scale debris flows transformed from ice avalanches or glacier collapse often result in dammed lakes and subsequent outburst floods that impose long-term impacts on downstream infrastructures and landscape evolution.