Anticipating future ice-dammed lakes across High Mountain Asia

Over recent decades, a significant increase in the amount and the size of glacier lakes has been observed. These lakes enhance glacier mass loss but also present societal hazard as they may retain large volumes of water. When large lakes drain, the downstream valleys can severely be impacted by the resulting glacial lake outburst floods (GLOFs), potentially leading to infrastructural damage and ecological impacts. Most studies assessing the future evolution and potential hazards from glacial lakes focus on proglacial lakes, i.e. lakes that are dammed by either moraines or bedrock. Albeit typically more hazardous, ice-dammed lakes including supraglacial lake are generally neglected in such assessments. 

Here, we assess for the first time the formation and development of potential ice-dammed lakes for all glaciers in High Mountain Asia. To do so, we model the geometry of each glacier by linking past digital elevation models to outputs of the combined glacier mass balance, ice flow and debris evolution model GloGEMflow. We identify potential ice-dammed lakes in depressions at the surface and margins of glaciers, and model their geometrical evolution by accounting for the enhanced melt caused by the lakes’ presence. The model is calibrated and evaluated with independent datasets. 

To analyze the ice-dammed lakes’ sensitivity to climate change, we model the evolution of glaciers and their ice-dammed lakes under different Shared Socioeconomic Pathways (SSPs). Our results indicate that the total number of potential ice-dammed lakes will first increase through time, and then diminish as glaciers shrink, reducing confining barriers. Compared to 2000, a moderate warming scenario (SSP126) anticipates approx. 42% more lakes by 2050, whilst in a strong warming scenario (SSP585), the increase is of ~46%. By the end of this century, the number of ice-dammed lakes will diminish compared to the 2050 peak by approx. 16%  (SSP126) and ~42% (SSP585) due to glacier shrinkage. The same pattern is also expected for the lakes’ volume evolution, which is expected to increase compared to 2000 between ~79% (SSP119) and ~87% (SSP585) by 2050, for then diminish by about 8% by the end of the century for SSP585 compared to 2050.  Finally, by investigating the largest ice-dammed lakes, we highlight regions that could be of particular relevance when aiming at anticipating future GLOFs from ice-dammed lakes.