Caroline Taylor, Rachel Carr

Supraglacial ponds are characteristic of debris-covered glaciers and can greatly enhance local melt rates. They can grow rapidly and coalesce to form proglacial lakes, presenting a major hazard. Here, we use Sentinel-2A satellite imagery (10 m) to quantify the spatiotemporal changes of 6,425 supraglacial ponds for 10 glaciers in Everest region of Nepal between 2015 and 2018. During the study period, ponded area increased on all glaciers, but showed substantial temporal and spatial variation. The rate of pond growth accelerated compared to 2000-2015 (Watson et al., 2016). Both Imja and Spillway Lake expanded and Khumbu Glacier continued to develop a chain of connected ponds. 54% of ponds were associated with an ice-cliff, but the proportion of ponds without cliffs decreased during the study period. Pond location generally corresponded to areas of lower surface velocity. Ideal conditions for pond formations have advanced up-glacier, and are now predominantly found at mid-elevations. Results indicate high-resolution imagery (< 10 m) is essential, as using Landsat data would miss 55–86 % of the total ponds found. Finally, glaciers were classified by stage of development (Komori, 2008; Robertson, 2012), with two transitioning between 2015 and 2018, suggesting lakes in the region are evolving rapidly. Furthermore, some glaciers displayed characteristics of multiple classes, so we propose an adapted classification system. Overall, our results demonstrate a trend of pond expansion in the Everest region and highlight the need for continued monitoring for hazard assessment.