That vanishing act made the Alpine glacier the site of a publicity stunt on Friday: the creation of what organisers say is the world’s largest postcard.
Climate change activists hope it will convince more young people to get involved in keeping rising temperatures in check.
In all, 125,000 postcards with messages against climate change and sent by young people from all over the world have been assembled around 3,400 metres up on the Jungfraufirn, the upper reaches of the Aletsch glacier.
This collection, organised by the Swiss government’s Agency for Development and Cooperation among other groups, includes the message “WE ARE THE FUTURE GIVE US A CHANCE”.
Another message on the snow – “STOP GLOBAL WARMING #1.5 DEGREES C” – refers to a United Nations report released last month.
Its scientists concluded limiting the increase in the Earth’s temperature to 1.5° Celsius – rather than the 2°C target agreed at the 2015 Paris climate talks – would provide clear benefits, but it would requires rapid, unprecedented changes in how people use energy.
Experts at the University of Zurich fear the Great Aletsch glacier, visible from space, could disappear by 2100.
It still measures 23km (14.3 miles), but it has receded about 3km since 1870, and the pace is accelerating.
The Aletsch glacier has melted so much that in 2012 the receding ice laid bare the remains of three mountain climbers, brothers who had disappeared nearly 90 years earlier on an ill-fated mountain expedition.
That is a far cry from the situation back in 1678, Swiss historians say, when residents of the valley below the Aletsch glacier prayed to the Vatican in Rome for the ice mass to stop its inexorable expansion that was threatening their lives.
Organisers of the postcard say the project will be climate-neutral.