Surface pond energy absorption across four Himalayan Glaciers accounts for 1/8 of total catchment ice loss

Glaciers in the high mountains of Asia provide an important water resource for millions of people. Many of these glaciers are partially covered by rocky debris, which protects the ice from solar radiation and warm air. However, studies have found that the surface of these debris-covered glaciers is actually lowering as fast as glaciers without debris. Water ponded on the surface of the glaciers may be partially responsible, as water can absorb atmospheric energy very efficiently. However, the overall effect of these ponds has not been thoroughly assessed yet. We study a valley in Nepal for which we have extensive weather measurements, and we use a numerical model to calculate the energy absorbed by ponds on the surface of the glaciers over 6 months. As we have not observed each individual pond thoroughly, we run the model 5,000 times with different setups. We find that ponds are extremely important for glacier melt and absorb energy 14 times as quickly as the debris-covered ice. Although the ponds account for 1% of the glacier area covered by rocks, and only 0.3% of the total glacier area, they absorb enough energy to account for one eighth of the whole valley's ice loss.