"
A new illustration of the impact of global warming
", "
a risk amplified by global warming
"... The day after the fall of the Marmolada glacier, which killed at least six people and injured eight, the press is unanimous: this dramatic accident is further proof that climate change can have disastrous conditions.
Italian Prime Minister Mario Draghi also pointed to “
the climatic situation
” as the main cause of this spectacular collapse.
Read alsoGlobal warming: the Alps are turning green and that does not bode well
This conclusion seems to be the easiest.
The largest glacier in the Dolomites massif, in northern Italy, the Marmolada suddenly collapsed, without any warning sign, even though this region of La Botte had just experienced a severe heat wave.
Popular route for hikers, it seemed secure.
Concretely, the glacier fractured at the level of one of the peaks of the massif, called Punta Rocca and located at 3309 meters above sea level.
So who else to blame, if not endemic heat?
An accumulation of melt water?
However, the culprit is probably a little too quickly denounced.
“
We still know relatively little about the causes of the collapse
”, tempers with Le Figaro Christian Vincent, specialist in the impact of global warming on glaciers at the Institute of Environmental Geosciences.
His transalpine colleagues gave him some preliminary information, but it is still too early to give any verdict.
For the time being, "
the origin of this serac fall is probably linked to meltwater from the surface, which penetrated the glacier and would have accumulated at the bottom
," says Christian Vincent.
As the melting progressed, the water pressure increased and reached the breaking point
”.
Like his Italian colleagues, the researcher does not yet understand how this water could have been trapped in the glacier.
"
In general, the water is retained inside the glacier because of its thermal regime: if the ice is at negative temperature, it is impermeable to water and forms a watertight dam
", explains our interlocutor.
In the case of the Marmolada, “
we can reasonably assume that its temperature is temperate, that is to say not negative, and therefore that the ice was not sealed
”.
But then, why was the water held back and not circulated?
This is what scientists are trying to determine.
Serac falls "
are not related to temperatures
"
If this hypothesis, linked to glacial hydrology, is accepted, it is indeed the ambient warming of the month of July that caused the surface ice to melt.
"
But not necessarily the global warming that caused the glacier to give way
," says Christian Vincent.
“
This region of Italy experienced two weeks of heat wave, which certainly led to an increase in melting.
But this heat wave is not unique in recent years.
Directly linking this rupture to global warming would therefore perhaps be a little abusive
, ”he develops.
In summary, establishing a direct link between this specific collapse and the climate which has been warming for several years could be like a shortcut.
Read alsoClimate guardians who have been reading glacier warnings for 50 years
Especially since serac falls are part of the usual operation of a high altitude glacier.
"
By definition, a glacier flows, and when it encounters a break in slope, it fractures
", recalls Christian Vincent.
In this specific case, “
the fracture occurred on a very steep slope
,” he adds.
In addition, serac falls “
are not linked to temperatures
,” insists the researcher.
They can happen at any time of the day and of the year
”.