Extreme climate effects on the occurrence and frequency of glacial debris flows: evidence from the Parlung Tsangpo Basin, Southeastern Tibetan Plateau

Under ongoing climate change, glacial debris flows are becoming a more important cryospheric hazard in high mountain areas, yet the effects of extreme climate on their activity remain insufficiently understood. This study investigates the spatiotemporal relationships between extreme climate and glacial debris-flow activity in the Parlung Tsangpo Basin, southeastern Tibetan Plateau, over the four decades from 1985 to 2024. Specifically, an inventory of glacial debris-flow activity was compiled using historical spaceborne photographs and Landsat imagery, and seven extreme temperature and precipitation indices were derived from two gridded meteorological datasets. The contributions of extreme climate indices to glacial debris-flow occurrence probability and frequency were then modeled separately at the decadal scale using logistic and zero-truncated negative binomial regression models, and their spatial correspondence with hotspots of the dominant extreme climate indices was finally examined. The results show that extreme warming and precipitation exert differentiated effects on glacial debris-flow activity. Temporally, the warm spell duration index (WSDI) makes the strongest contribution to glacial debris-flow occurrence probability (2.16%), whereas the maximum consecutive 5-day precipitation amount (Rx5day) contributes most strongly to glacial debris-flow frequency (2.57%). Spatially, WSDI hotspots exhibit little overlap with glacial debris-flow hotspots, whereas Rx5day hotspots display much stronger co-location. Overall, the study highlights that prolonged warm extremes mainly enhance long-term predisposition, while multi-day precipitation extremes are more closely associated with triggering conditions, implying that regional hazard assessment and early warning of glacial debris flows should account for both short-term extreme wet conditions and preceding periods of sustained anomalous warmth.