Ludo Ravanel is a researcher, glaciologist and geomorphologist, mountain guide at the Chamonix Guides Company and science communicator. He comes from one of the oldest families in the Chamonix valley, whose roots can be traced until the 1300’s. Behind him there are several generations of guides, including his father, and the high mountains are an environment where he was immersed since an early age. Young, he used to visit the chalet in the Aiguilles Rouges Reserve, trying to learn as much as he could about mountains. He studied geology and geomorphology, to better understand the environment where he loved to practice rock climbing and alpinism. After doctoral and post-doctoral contracts in France and Switzerland, he joined the CNRS in 2014. Today, his work is 100 % dedicated to understanding the high mountains environments, especially in the context of climate warming.
This interview was taken mid-august 2020 at the Montenvers Train Station overlooking the largest glacier in the French Alps, Mer de Glace. Around the train station, situated at 1913 m altitude, rise Les Drus, Les Grandes Jorasses, Les Grands Charmoz and in the background, the Aiguille de Blaitière.
[A.B.- Anca Berlo]: Can you describe your work as a high mountains researcher?
Ludo Ravanel: A part of my work takes place in the mountains; however, it is not the most important. I do field work pretty much all throughout the year, but between the end of August and the end of October this work becomes more intense, as I observe, measure, take data and do sensor maintenance. These data are then processed, analysed and discussed at the EDYTEM lab in Chambéry, which is dedicated to the study of dynamic of mountain territories. What follows, and I consider an important part of my work, is communicating this scientific information, in both the science world as well as towards the public at large. I do this via popularisation papers, conferences, terrain visits, etc.
[A.B.]: Which is your role here at Montenvers Train Station, above Mer de Glace?
Ludo Ravanel: Glaciologists have been hired for the past 10 summers by Compagnie du Mont-Blanc to explain visitors the evolution of the mountains and the fast evolution of the glacier. Often, tourists are very disappointed by what they see here.
Some tourists had visited the glacier 20 years ago, saw it white and beautiful and do not understand its present state. Some tourists have never been here but have expectations based on images from the 80’s that continue to circulate. We are here to explain what happens, to educate and to raise awareness towards the effects of climate change.
Mer de Glace Glacier / Chamonix Mont-Blanc
[A.B.]: Mer de Glace is losing 4,3 m of ice per year in depth and several tens of meters in length. Will it eventually disappear?
Ludo Ravanel: In terms of loss of length and depth, it is worse, because 4 m per year is the average in terms of loss in depth during the first years of monitoring. But these last years we have witnessed a multiplication of summer heat waves – 2015, 2017, 2018, 2019 – and every time we lose around 6 to 8 m. It is a very fast process and what we know is that around 2050 the two glaciers that feed Mer de Glace – Tacul and Leschaux Glaciers – will disconnect, therefore, Mer de Glace, as we toponymically see it on maps, will not exist anymore. Two lakes will take their places – one small, in the lower part and one bigger, higher up. So the scenery will change a lot.
[A.B.]: Is the warming process we now experience, normal?
Ludo Ravanel: During the past 12.000 years we have been in an interglacial period, called the Holocene, which has seen climate fluctuations with warmer periods than the one we go through, as well as colder periods.
The last small cold age was between 1250 and 1850. In this Little Ice Age, it was colder, there was more snow, so the glaciers regained volume mostly comparing to the Middle Ages, as they were a bit smaller than today. In 1644, glaciers were even destroying villages.
We are now in a period of natural climate warming. However, an added greenhouse effect linked to human activities adds up, which accelerates this warming. By studying the atmosphere, we are able to identify which gasses with greenhouse effect come from natural sources and which have an anthropic origin. Today we know that the anthropic climate warming is more important than the natural climate warming. It is this greenhouse effect linked to human activities that makes the heating happen too fast.
[A.B.]: How long will this climate warming cycle last?
Ludo Ravanel: Year 1970 was very important. Had we stopped all of a sudden all the greenhouse emissions the natural character of the climate would have continued. Today, even if we stopped all greenhouse emissions, which is not possible, the climate would continue to warm artificially for several decades, even centuries. The best we can do is to limit the climate warming. We can not reverse it.
Aiguille du Midi / Chamonix Mont-Blanc
[A.B]: What is permafrost and why is it important?
Ludo Ravanel: We talk a lot about glaciers, but actually we have another problem, the degradation of the permafrost, which is all the ground materials that are permanently frozen. It keeps ice in cracks and this ice has a cementing role. When permafrost disappears, whole mountains sides can destabilise. This is what we study in the French Alps, since 2005, especially at Aiguille du Midi, which has become for us a real laboratory.
The permafrost is a thermal state, that is not seen, and if we want to identify where it exists, we first have to measure the rock temperature, to better understand what drives this temperature so then we can model the data. Today, we have a map of the distribution of permafrost in the Mont Blanc massif and this is due to temperature measurements done at Aiguille du Midi.
First, we have installed temperature sensors at the rock surface to try to better understand the distribution of permafrost. However, we did not contend to install temperature sensors only at the surface. Today, when we talk about laboratory I mean we have a large variety of methods, we have temperature sensors in depth, in 3 boreholes, 10-m-deep each, in the North, South, and East faces and all along these 10 m we have installed 15 temperature sensors in each borehole. We measure the temperature since 2009. We have 10 years of data which have allowed us to evaluate how permafrost evolves and if we make the average at 10 m depth on the 3 boreholes, we see that it warms by 1 – 1,5°C each 10 years. This is enormous and it is more that the warming of air temperature. It creates problems because the ice in the cracks melts and we have witnessed for the past 2-3 decades a multiplication of rockfalls in high volume. This creates the risk of infrastructure destabilisation – refuges, cable cars, risks for alpinists, as well as risks for the valleys through what we call “cascading effects”: a rockfall triggers a snow or ice avalanche which can reach a valley. It was the case, at the end of August 2017, when during the end of a summer heatwave, in the Switzerland Alps, in the Canton of Grisons, 3.1 millions m3 have fallen, taking with them a glacier. It all moved 6 km, sweeping away a village. Fortunately, we were expecting this phenomenon, the mountain was being monitored, and that allowed people to be evacuated in time.
To return to Aiguille du Midi and to our present work there – we do high resolution topographical measurements to see if the rock moves, we do extensiometric measurements – there are sensors at crack level which allow us to see if the fracture opens or closes and it offers pretty interesting results. We also do geophysics – cables are stretched from the summit, descended on the South, East, and North faces, a bit like a squid, they are connected to the rock, then we pass electricity through the wall, and depending on the electrical signal received (resistivity), we manage to deduct the temperature and ice contents in the cracks.
[A.B.]: Two days ago, we had rock falls on the Mont Blanc ridge, while generally that happens only on the Grand Couloir. Last week, a snow bridge collapsed on the Vallée Blanche and the small village of Val Ferret on the Italian side is evacuated again due to risk of collapse of the Planpicieux glacier. What exactly is going on?
Ludo Ravanel: For a few decades, we have witnessed a period of climate warming, we see this in the mountains, with an increase in rock destabilisation, but also glacier destabilisation and in the heart of this climate warming are summer heatwaves that multiply. During these conditions, the permafrost degrades, especially from the surface through what is called the “deepening of the active layer”.
The active layer is the one that unfreezes every year, and the more canicular episodes we have the thinner it becomes, which eventually provokes a multiplication of rockfalls, like the ones we see in the Grand Couloir of Goûter, which can be dangerous for climbers. On glaciers, we see the snow bridges become less and less resistant, and tragic accidents can happen. Just a few days ago, a colleague and guide died because an enormous bridge sank.
In the case of the Planpicieux glacier, its evolution is also linked to this climate warming, reinforced by this canicular episode that we just had. What happens is that ice is melting in large quantities, producing liquid water which lies underneath the glacier. This water will allow the lubrication of the base of the glacier, facilitating its sliding, and as glaciers are retreating on steep slopes they can destabilise easily, which may happen in this specific area of the Mont Blanc massif.
[A.B.]: Can we estimate when a serac will fall?
Ludo Ravanel: A serac is an ice tower surrounded by a certain number of crevasses and, unfortunately, there are not too many ways of knowing when a serac will fall, because a fall of a serac is something normal in the vertical part of a hanging glacier. It happens independent of the climate change. It is just our experience that will tell us that a certain configuration, on a downstream, under-hanging face, will fall, so we will try to avoid to pass underneath it.
[A.B]: How does climate change affect alpinism?
Ludo Ravanel: Alpinism is the traditional activity in the high mountains. In 2015 we celebrated 150 years of the golden age of alpinism, since 1865 when a significant number of first ascents were made. All along the history of alpinism, we had changes, notably linked to social causes and technical – equipment related reasons. Nowadays alpinism is facing the climate challenge, because the warming has changed the alpinists’ playground. With the retreat of glaciers, the disappearance of ice covering the North faces, the degradation of the permafrost which in turn multiplies the rockfalls in the walls, alpinists must quickly adapt. We have identified 33 ways of adapting, which are presented in the PhD thesis of Jacques Mourey*, and we can group them in 5 categories:
- SEASONALITY. First, there is a change in seasonality, the traditional alpinism that we practiced at the end of July-August is now moved to spring or even full winter, so that the mountain is in good conditions.
- ACTIVITY CHANGE. We see a change in activities, less traditional alpinism, more canyoning, more via ferrata, more activities not so high up in the mountains.
- REACTIVITY. More reactivity is needed from alpinists to good conditions, which means that we can still have good conditions but in shorter periods of time and in less classical moments of the year. For example, in 2015 we had a summer heatwave, but in September weather was very bad, therefore conditions in the North face of Grandes Jorasses became excellent.
- MOBILITY. It means that when conditions and not good in Écrins Massif we move to Mont Blanc massif, or in the Valais, or in the Bernois Oberland. This is paradoxical, as this adaptation method produces movement, and in turn greenhouse effects.
- EQUIPMENT. Sectors which are now dangerous due to rock fall can be avoided by new routes, by installing equipment. We think mostly of access to high mountain refuges. Here at Montenvers, Mer de Glace basin gives access to 5 refuges which become harder and harder to access, we have today almost 700 m in stairs in order to be able to reach the refuges. So we can still equip the high mountain, but until when, this calls for responsibility, financial involvement and environmental thought.
* “L’alpinisme à l’épreuve du climat dans le massif du Mont-Blanc : évolution des itinéraires de haute montagne, impacts pour les pratiquants et outils d’aide à la décision”.
PhD thesis author: Jacques Mourey.
Thesis coordinator: Ludo Ravanel.
Interview “Ludo Ravanel – Alpinism is now facing the climate challenge” by Anca Berlo
Chamonix Mont-Blanc 13/08/2020