Vik: Icelandic seventh-grader Lilja Einarsdottir is on an unusual field trip with her class: they're measuring the Solheimajokull glacier to see how much it has shrunk in the past year, witnessing climate change first-hand.

"It is very beautiful but at the same time it is very sad to see how much it has melted," says Lilja, bundled up against the autumn chill in a blue pompom hat.

Each October since 2010, now-retired schoolteacher Jon Stefansson has brought students aged around 13 from a school in Hvolsvollur a village about 60 kilometres away to the glacier to record its evolution.

The results are chilling: nestled between two moss-covered mountain slopes, Solheimajokull has shrunk by an average of 40 metres per year in the past decade, according to the students' measurements.

On this blustery October day, the youngsters armed with a GPS, a measuring tape and two yellow flags calculate the distances on foot from various spots, struggling against strong winds.

The numbers on the sign, pitched in black sand and steadied at the base by a pile of stones, indicate how many metres of ice have disappeared over the past years: "24", "50", "110".