"
It's the driest winter since 1959.
"
The Minister for Ecological Transition and Territorial Cohesion, Christophe Béchu, declared on Wednesday February 22 that France was
"in a state of alert"
.
And if the rain should return this Wednesday, after 32 days without precipitation, we are already worried in the mountains about the consequences of this exceptional drought for the glaciers.
The ice that sits enthroned at high altitude has already suffered last summer when all melting records were beaten.
"
In the Swiss Alps and in the Mont-Blanc massif, the glaciers have lost an average of 6% of their volume
", indicates Ludovic Ravanel, geomorphologist who heads the joint research unit Edytem (University of Savoie Mont-Blanc, CNRS ).
And the phenomenon concerned all the French mountains, adds the scientist.
A melt greater than the year 2003 of the great heat wave and the very hot summer of 2015.
After a murderous season, the glaciers therefore had the opportunity to restock with the precipitation of this winter.
“
They accumulate snow at altitude, and generally reach their maximum thickness at the end of February
,” says Ludovic Ravanel.
Glaciers melt mainly in summer, but this accumulation plays a very important role in summer mass loss.
Read alsoAntarctica: first deep dive to study the melting of a giant glacier
“
Winter and spring precipitation brings very white snow, which, depending on the albedo effect, reflects solar radiation back into the atmosphere
,” explains Emmanuel Thibert, INRAE glaciologist.
If the sun beats down on bare ice, or on old layers of snow that lose their ability to reflect solar energy as they turn to ice over a few years, the melting is much faster.
First measurements in spring
Today, the glaciers are therefore not replenished over their usual period and the summer season is likely to be complicated.
“
The mass balance could once again be very negative
,” fears Ludovic Ravanel.
"
It looks bad
," confirms Emmanuel Thibert.
The first field measurements will be taken at the end of spring and will be able to precisely determine the damage caused by this drought.
In the meantime, spring could hold surprises in terms of snow cover.
It is common to have heavy snowfall in the mountains in April and May.
“
It is difficult to recover in any case
, indicates Ludovic Ravanel.
I tried to reassure the mountaineers, because there was hope at Christmas, but the snows at the end of the year did not continue at all
”.
The practice of mountaineering in certain high mountain sectors is strongly conditioned by the good health of the glaciers.
When they are poorly filled, the snow bridges that mask the crevasses can give way.
A mountaineer thus made a fatal fall of 15 meters in a crevasse on February 8 in the Mont-Blanc massif on the Rognons glacier.
For about three decades, the glaciers have entered a phase of shrinkage.
They had increased in volume during a little ice age which had ended in the 1850s. After new episodes of growth in the 1920s and 1980s, they are now constantly melting under the effect of global warming.
