European Space Agency, 25 May 2022

Rain fell on the highest region of the Greenland Ice Sheet for the first time ever recorded during the summer of 2021. Several intense “atmospheric rivers” in combination with a heatwave swept along Greenland, elevating summer temperatures above freezing. Atmospheric rivers are warm, meandering air currents filled with moisture from the tropics. When they flow near Greenland, they push warm air above the ice sheet and accelerate the melting of surface snow and ice, as well as turning snowfall into rainfall. Last summer, these warm winds completely removed the surface layer of snow across the lower third of the ice sheet. Loss of the insulating snow cover, in addition to the formation of meltwater ponds exposed more of the dark surface of the ice to the sun. Together, these factors created a positive feedback loop that accelerated ice loss and meltwater runoff into the ocean. As global temperatures rise, the frequency and magnitude of Greenland heatwaves becomes greater, increasing the likelihood of similarly unprecedented rainfall events in the future.