Above the poles
Towed by a sailboat in Greenland’s fjords, an atmospheric measuring balloon overlooks the turquoise sea. Its designer describes how it works and how it aims to document the link between melting ice and cloud formation.
Photo: Roman Pohorsky
With its two masts pointing towards the sky, the schooner glides quietly among the floating ice of the Ikersuaq fjord, at the southwestern tip of Greenland. Above this wild arctic setting is a compendium of engineering. It’s a balloon inflated with helium and stabilised by a wing, and it’s attached to the boat by a discreet rope. On board the balloon is a mini-research station: Avatar. Roman Pohorsky, who designed it, submitted this shot immortalising its first flight during the Greenfjord project to the SNSF Scientific Image Competition 2026.
In the summer of 2025, Pohorsky – an EPFL postdoc specialising in atmospheric sciences – set out on the sailboat Forel, travelling the Arctic with six scientists and six crew members. He was apprehensive about Avatar’s first launch: “I’d planned an hour and a half for take-off, in anticipation of problems”. From a stuck winch to a torn printed circuit board connecter, there had been no shortage of possible issues. “In the end, it only took five minutes!”, he says smiling. The new automated prototype works: it has an on-board computer managing the winch to regulate altitude and measurements in the sampling chamber, all according to a pre-established flight plan. “After you press ‘Start’, unless you want to change something along the way, it’s good until it’s come back down”. That meant Pohorsky could spin up a drone and take pictures of Avatar whilst its onboard lasers measured the number, size and composition of aerosols and droplets in the air.
The goal is to compare the aerosols above fjords which end with the mainland and those which end with glaciers. Where there are more of these particles, it favours the formation of droplets, and hence the condensation that initiates cloud formation. “It is essential to anticipate the consequences of melting ice on atmospheric phenomena at the poles, which can in turn impact the global climate”, says Pohorsky. His system has not concluded its work yet: one unit will leave for the Arctic aboard the Tara Polar Station in July 2026 while another will fly over Antarctica from 2027 off the Polarstern ship.
