In total 1.5 billion cubic metres of ice was lost from the 20 Swiss glaciers measured during the period October 2016 to September 2017, said the Swiss Academy of Natural Sciences in a statement on Monday.
The calculation is the difference between the volume accumulated due to snow and the amount lost due to melting.
“Glacier melt was extreme during summer 2017 – at a national level glaciers lost more ice than they did during the heatwave of summer 2015 and nearly as much as in 2011,” the Academy said.
The figure is enough to fill one 25 metre swimming pool for every household in Switzerland and is among the three biggest losses since records began a century ago, after 2003 and 2011.
The near-record ice melt was partly due to a mild winter with less snow than normal, said the Academy.
Last December was the driest and least snowy in 150 years. Though snow did fall in January, February was also too dry. That was followed by a hot summer, with mountains losing snow cover around a month earlier than normal.
Only a wet August – marked by a huge landslide on the Piz Cengalo mountain in Graubünden – and a colder than average September prevented the glaciers from losing even more volume, it added.
Glaciers melted more than normal across the country, said the Academy, though some in the Valais and the Bernese Oberland suffered particularly high losses, of around 2-3 metres of their thickness.
Among those mentioned by the Academy is the Tsanfleuron glacier, where in July the remains of a local couple who went missing in 1942 were finally discovered.
Shifting ice also led to the discovery, in August, of the body of a German hiker who went missing in 1987 on the Hohlaub glacier near Saas-Grund in the Valais.
In September, residents of nearby Saas-Fee were evacuated shortly before the tongue of the Trift glacier collapsed. Geologists had been monitoring it for a while and had detected significant movement, up to 130cms a day.
The melting of the mighty Aletsch glacier – the longest in the Alps – is causing the land next to it to slip at dramatic rate, scientists discovered in January.
Prior to 1995 adjacent land at Moosfluh moved at an average rate of less than one centimetre a year; after that point it began moving at 30 centimetres a year, they said.
Some 150 years ago the Aletsch was around three kilometres longer and 200 metres higher than it is now.
Meteorologists said on Monday that the month of October was around 1-3 degrees warmer than normal in Switzerland, extremely dry and the sunniest on record in some parts of the country.