Satellite-observed surging dynamics of North Kunchhang Glacier I in the Eastern Karakoram

Abstract. Frequent glacier surges are a distinctive characteristic of Karakoram glaciers, with their increased occurrence profoundly impacting glacier morphology and dynamics. However, limited and short-term observations have constrained our understanding of surging dynamics and their underlying mechanisms. This study employs extensive multisource remote sensing data to investigate long-term, multi-phase changes in flow velocity, surface elevation, and terminus position of North Kunchhang Glacier I (NKG I) in the Eastern Karakoram. By examining 25 years of changes, we identified the timing of glacier surges, estimated mass transfer during surging events, and analysed spatiotemporal correlations among key variables. Historical interpretation of terminus dynamics dating back to 1972 revealed a prior main trunk surge around 1980, enabling an exploration of potential climate change impacts on surge behaviour. Our results indicate that the 2017 main trunk surge lasted four years (June 2015‒June 2019), transferring ~ 0.45 Gt of glacier mass, inducing significant downstream elevation gain, and leading to a delayed terminus advance starting in 2018, three years after the surge initiation. In contrast, the 2004 surge of NKG V (within the NKG basin and connected to NKG I after surge) lasted 2.5 years (November 2002‒April 2005), transferring ~ 0.23 Gt of glacier mass, destroying a proglacial lake, and raising its surface elevation by ~ 180 m. Flow velocity, surface elevation, and terminus position derived from various sources exhibit strong consistency in both trends and values, confirming the reliability of our results. Notably, the 2017 surge exhibited a shorter rapid advance period compared to the 1980 surge, suggesting that climate change may be influencing surge mechanisms, leading to smaller-scale but more frequent events. These findings provide new insights into the surging dynamics of NKG I and contribute to a deeper understanding of Karakoram glacier behaviours. The integration of multisource remote sensing demonstrates its critical value in deciphering complex glacier dynamics and their responses to a changing climate.