Duo Chu,Caiwang Dunzhu,Lawang Dunzhu,Suolang Tajie,Pingcuo Sangdan,Zhaxi Duoji,Mingma Ciren,Cuo Ping
Sentinel-2 is a high-resolution optical Earth observation mission within the GMES (Global Monitoring for Environment and Security) programme, which is renamed Copernicus in 2012, jointly implemented by the EC (European Commission) and ESA (European Space Agency) for global land observation with high revisit capability to provide enhanced continuity of data so far provided by SPOT and Landsat. Copernicus is the most ambitious Earth Observation programme to date. It provides accurate, timely and easily accessible information to improve the management of the environment, understand and mitigate the effects of climate change and ensure civil security. At present, Sentinel-2 is one of the most important data source for remote sensing monitoring and application research, and has been widely used in monitoring natural disasters such as floods,forest fires, landslides, volcanic eruptions, and emergency response and humanitarian crises around the globe,and there are also great potentials in detecting glacier and ice and supporting relief efforts for cryospheric disaster.In this study, the glacier and ice avalanches occurred in Arutso Lake basin in northwestern Tibet and Sedongpu basin in southeastern Tibet in 2016 and 2018 were investigated using Sentinel-2 images and field surveys, and the evolution process of two events were reproduced, which has important reference significance for monitoring cryospheric hazard, emergency relief and management in other mountain regions on the world.Study shows that Arutso No. 53 glacier avalanche completely melted away in July 2018 after lasting for two years from occurrence to final disappearance, while the area of Arutso No. 50 glacier avalanche is 0.58 km2 left on June 22,2021 because of more thickness compared to Arutso glacier No. 53. Four large-scale ice-rock ava lanche and debris flow events in the Sedongpu basin in 2017 and 2018 not only had significant impacts on the river flow, landscape and landform in the basin, but also caused great disasters in the basin and downstream.Two glacier and ice avalanche events were caused by climate warming and local heavy precipitation, acting on specific topographic and geomorphic structure of glacier properties in high mountains. Specifically, Arutso glacier avalanche was caused by climate- and weather-driven external forcing, acting on specific polythermal and soft-bed glacier properties and is an unprecedented large catastrophic instability of low angle mountain glaciers. Glacier and snow melting caused by climate warming and heavy rainfall are main triggering factors for ice and rock avalanche in the Sedongpu basin, which is a typical hazard cascades originating from cryosphere, followed by rock fall, debris flow, dammed lake, and lake outburst flood disaster. It often occurs in the Sedongpu basin and will continue to occur for a long time in the future, and the high mountain ridge covered with ice and snow in the right side of back of the basin is still a high-risk area for ice and rock avalanches in the future.