Mont Blanc, the summit of Western Europe on the French-Italian border, was measured in September at 4,805.59 meters. The announcement was made this Thursday, October 5 by a team of French surveyors, leaving it to the scientists to “ explain this phenomenon “.
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Armed with cutting-edge tools and equipped for the first time with a drone, around twenty people divided into eight ropes climbed the white giant in mid-September in order to carry out point-by-point surveys for several days, as they do every two years since 2001.
This is the 12th edition of this operation which aims in particular to model the ice cap and collect scientific data on the impact of climate change on the Alpine mountains, specify the participants in this initiative, launched in 2001 by the chamber. expert surveyors from Haute-Savoie – a department bordering Italy –, which today brings together several partners.
“ I announce to you that this year the measurement of Mont Blanc was 4 805.59 meters. We have a variation of 2.22 meters » compared to the previous measure of 2021, indicated Jean des Garets, president of the chamber, during a press point in Chamonix. “ It is now up to climatologists, glaciologists and other scientists to exploit all the data collected and put forward all the hypotheses to explain this phenomenon. », conclude the experts, emphasizing that their own role is limited to “ accumulate data for future generations “.
Dune complex
During the last expedition of the same type, in 2021, the roof of the Alps was measured at 4,807.81 meters, almost a meter less than the measurement taken in 2017 – that of 2019, very low, had been kept secret, because it was considered unrepresentative. Conversely, it was in 2007 that the highest altitude was recorded at 4,810.90 meters. These variations are not surprising, warn the surveyors, because “ since the dawn of time, the altitude of Mont Blanc has continuously oscillated “.
The top ” rocky » of the mountain culminates at 4,792 meters, but it is the thickness of the layer of “eternal snow” which covers it, functioning like an enormous snowdrift, which “ varies depending on altitude winds and precipitation », They detailed in 2021. The altitude of the summit also varies according to the seasons, Mont Blanc being a dune complex where the wind, more violent in winter, scrapes the snow more than in summer. The summit is therefore higher at the end of the summer than in spring.
While the melting of glaciers is accelerating under the effect of global warming, which particularly affects the Alpine arc, one of the members of the team, Denis Borel, called for “ stay humble » and not « not draw hasty conclusions on measurements which have only been carried out since 2001 with the precision » current.
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Mont Blanc in three figures
2,426 toises. Or 4,728 meters above the Mediterranean. It is, according to XYZ, the journal of the French-speaking Association of Topography, the first known measurement of the altitude of Mont Blanc, carried out in 1695 by the Geneva surveyors Jean-Christophe and Nicolas Fatio de Duillier. Over the following centuries, many scientists made their measurements. The exercise became more precise from 1986 thanks to GPS. The summit is measured between 4,807 and 4,811 meters depending on the year. The altitude of Mont Blanc now stands at 4,805 meters and 59 centimeters, according to the new measurement unveiled this Thursday.
20,000 climbers per year. Each year, between 15,000 and 20,000 people attempt to climb Mont Blanc mainly in summer, according to the prefecture of Haute-Savoie, the department in eastern France where Mont Blanc is located. To avoid overcrowding, a maximum of 214 climbers per day is set for the summer of 2019 by the mayor of Saint-Gervais, the town from where the classic route to the Alpine giant leaves. This corresponds to the number of places available in the Mont Blanc refuges.
10.4°C. On June 18, 2022, this record temperature was recorded at the summit of Mont Blanc. During this heat episode, temperatures even remained positive for 11 consecutive hours, causing “prolonged melting at the summit of Mont Blanc”, according to the Regional Environmental Protection Agency (Arpa Val d’Aosta). The weather station which allowed these measurements has been installed since 2015 in the immediate vicinity of the summit, on Col Major (4,750 meters). The temperature rarely exceeds 0°C and regularly drops below -30°C in winter.
(With AFP)