Mont Blanc, the tallest mountain in the Alps, has shrunk by 2.2 metres since 2021 to its lowest height in recent memory.
The mountain, which is capped by a ridge of ice covering the rock, was measured by a team of surveyors from the Haute-Savoie regional administration, aided by a drone.
The results, published on Thursday, suggest the new official height of Mont Blanc is 4,805.59 metres. The previous reading, taken two years ago, recorded the summit at 4,807.81 metres, which was in turn almost a metre less than the measurement taken in 2017.
Describing 2023 as a “somewhat exceptional year”, one of the surveyors involved, Denis Borel, told the French televisions channel TF1 that the mountain had lost “3,500 cubic metres of ice and snow compared to the volume measured in 2021, representing roughly the volume of an Olympic swimming pool”. Borel said the loss was “quite considerable compared to the measurements of previous eras”.
Climate and glaciology experts cautioned against linking the shrinking of Mont Blanc’s summit to the loss of glacial ice cover in the Alps.
“Even if we see that there is a slight downward trend – around 15 to 20cm since 2001 – of this snowy summit of Mont Blanc, climatologists and glaciologists tell us that it takes approximately 50 years of measurement to be able to draw conclusions on possible global warming at this altitude of 4,800 metres,” said Borrel. Ice cover at the summit of Europe tended to experience variation, depending on wind and precipitation, he said.
“This is not representative of global climate warming, because the climatic conditions at the summit of Mont Blanc are rather polar,” said Luc Moreau, a glaciologist from Chamonix.
Moreau described a process called ablation in which wind accelerates evaporation. “It is mainly the wind and the snow which will influence the altitude of the summit. The wind will remove the snow or not,” he said, adding that the summit dome of Mont Blanc is more like a “dune complex” with strong winter winds stripping snow from the summit.
The 2.22-metre decline could be down to lower precipitation during summer, said Jean des Garets, chief geometer in the Haute-Savoie department of south-eastern France. “Mont Blanc could well be much taller in two years,” when it is next measured, he added.
The mountain’s rocky peak measures 4,792 metres above sea level, but its thick covering of ice and snow varies in height from year to year depending on wind and weather.
Researchers have been measuring it every two years since 2001, hoping to garner information about the impact of climate change on the Alps.
“We’re gathering the data for future generations, we’re not here to interpret them, we leave that up to the scientists,” des Garets said.
“After these measurement campaigns, we have already learned a lot: we know that the summit is in perpetual movement both in altitude with variations of almost 5 metres, and in position.”
The impact of global warming has been well documented in the Alps. Its glaciers have lost a third of their volume in recent years and the mountain range has also lost permafrost – soil and rocky material that stays frozen continuously for at least two years and acts as a glue for major mountain features – above an approximate height of 2,200m.
