Glacial lake evolution and glacier-lake interactions in the Poiqu River basin, central Himalaya, 1964-2017

Despite previous studies, glacier-lake interactions and future lake development in the Poiqu River basin, central Himalaya, are still not well understood. We mapped glacial lakes, glaciers, their frontal positions and ice flow from optical remote sensing data, and calculated glacier surface elevation change from digital terrain models. During 1964-2017, the total glacial-lake area increased by similar to 110%. Glaciers retreated with an average rate of similar to 1.4 km(2) a(-1) between 1975 and 2015. Based on rapid area expansion (>150%), and information from previous studies, eight lakes were considered to be potentially dangerous glacial lakes. Corresponding lake-terminating glaciers showed an overall retreat of 6.0 +/- 1.4 to 26.6 +/- 1.1 m a(-1) and accompanying lake expansion. The regional mean glacier elevation change was -0.39 +/- 0.13 m a(-1) while the glaciers associated with the eight potentially dangerous lakes lowered by -0.71 +/- 0.05 m a(-1) from 1974 to 2017. The mean ice flow speed of these glaciers was similar to 10 m a(-1) from 2013 to 2017; about double the mean for the entire study area. Analysis of these data along with climate observations suggests that ice melting and calving processes play the dominant role in driving lake enlargement. Modelling of future lake development shows where new lakes might emerge and existing lakes could expand with projected glacial recession.