As we passed the town of Saint-Gervais-Les-Bains on the French highway, en route to a sampling campaign, Mont Blanc’s glaciated terrain suddenly emerged above the spring foliage. Breaking the silent awe, Patrick remarked that indeed, “Mont Blanc is still there.”
The Mont Blanc Massif towers over us as we drive towards Chamonix, France (Photo Credit: Kara Sampsell, May 2025)
The humor won’t be lost on anyone familiar with the massif. Its unquestionable, human-minimizing presence colours the regions’ cultural and economic character. Alpinists have pursued its summits since the 1700s and it remains a global hub for mountain sports. However, the terrain calls to more than just athletes. The Mont Blanc Massif is also the focus of researchers in France and beyond.
Novel approaches which combine microbiology and chemistry in glacial environments shake up paradigms that don’t group ice and life together. In doing so, there is a lot to be learned. From the base of Mont Blanc’s glaciers to its highest ice-covered peaks, researchers explore how microbial life and chemical traces in snow, ice, and sediment reveal stories of past and present ecological change.
We enter a subglacial cavity beneath Glacier d’Argentière and glacial rock flour sediment can be seen on the ceiling of ice (left). Dr. Catherine Larose stands between the bedrock and glacial ice with a sediment sample in hand (right). (Photo credits: Kara Sampsell, February 2024)
My own PhD research took me beneath Glacier d’Argentière in search of fine glacial sediment in February 2024. We aimed to learn what kind of microbes inhabit the sediment and what genes they have. As glaciers melt with global warming, ice-free glacial forefield areas expand and glacial sediments are deposited there. One of our goals is to understand whether microbes make the sediment-rich land more hospitable to advancing flora by increasing nutrient access. To answer this, we needed to sample the subglacial rock sediment known as glacial flour which is produced beneath the glacier.
Our pursuit of the samples began in what appeared to be a normal building, but we quickly found ourselves in a system of rock enclosed tunnels. This subglacial network is part of the hydroelectric infrastructure capturing energy from Argentière’s meltwater. Yet, as our guide led us into a glacial cavity where its velocity is continuously recorded, any pretense of human control over the environment evaporated. The light from our headlamps gleamed off the undulating blue-hued ceiling of basal ice. We were in the belly of a beast.
The bright orange of the tent isn’t a challenge to spot with clear weather at the Col du Dôme. (Photo credit: Kara Sampsell, May 2025)
After studying diagrams of subglacial dynamics at my desk, I finally found myself at the interface where the movement of the ice makes flour from rock. We excitedly collected the fine sediment directly off of the basal ice surface. Back at the lab, I extracted DNA from the glacial flour and used next generation sequencing to learn which types of microorganisms colonize sub-glacial glacial rock flour and how they may be able to influence the ecosystem.
Just as microbes from beneath the glacier may shape future ecosystems, those preserved within the ice tell us about ecosystems long past. Decades of chemical traces and DNA from airborne microbes trapped in glacial ice form a layered archive of past atmospheric conditions. To study this archive, our lab’s goal was to drill an ice core from the Col du Dôme (4,250 m a.s.l.).
The team unpacks drilling equipment (left) and sets up the ice core drill (right). The CNRS’s Vallot refuge where the main drilling team would be sleeping during the drilling period can be seen in the distance beyond ski tracks (left). (Photo Credits: Kara Sampsell, May 2025)
Along with the primary drilling team, several loads of gear to set up the drilling operation were transported to altitude by helicopter. Two days later we were joining them for the morning to get a taste of how the work is done. With the howl of the helicopter, views of the cozy valley quickly gave way to the majesty of crevassed glacial terrain. The bright orange drilling tent became visible between smooth white snow and shocking blue sky as we descended.
Seasonal snow accumulation found in the first few metres of cores is the focus for Francesca Schivalocchi. Through her PhD research at Col du Lautaret (France), she infers sources of sugars in the snow related to the surrounding environment like vegetation or biomass burning. As she put it, “The goal of this (Col du Dôme sampling) is to sample snow from a higher altitude than Col du Lautaret (2000 m a.s.l.). It offers a different environment with distinct seeding sources”. The difference in environmental constraints and inputs may lead to distinct patterns of microbial activity which influence community structure, carbon cycling, and broader ecosystem processes in the snow.
“Can you hold these screws?” The materials for drilling need to be assembled and checked at the site before drilling begins (left). Once the team has successfully drilled and documented the ice cores, they are stored in these styrofoam boxes and transported by freezer truck to a freezer warehouse for long-term storage (right). (Photo Credits: Kara Sampsell, May 2025)
Over time, snow becomes ice at Col du Dôme. This ice is at the heart of Catherine Larose’s project (ERC-funded Paleo-MARE) and the PhD research of Marie Labat Saint Vincent. The chemical and microbiological archive in the ice enables investigation of whether these anthropogenic pollutants like heavy metals may have driven evolution of antibiotic resistance through long-term selective pressure.The paired chemical and microbiological archive also underlies the project of Marie, who says that for her, “It is a question of evolution”. Her research explores whether the frozen microbial communities reflect those once present in the atmosphere. With next generation DNA sequencing, she compares microbial communities from ice core samples to those from historical atmospheric filters to understand how microbial diversity and functions evolve under environmental pressures. This approach allows a glimpse at past ecosystem evolution–no time travel needed.
The drilling mission team (left to right): Dr. Patrick Ginot, Harpreet Singh, Olivier Alemany, Dr. Bruno Jordain, Stephanie Dumont, Dr. Catherine Larose, Marie Labatt Saint Vincent, Kara Sampsell, Francesca Scivalocchi (Photo Credit: Stephanie Dumont, May 2025)
Aside from the popular aesthetic and physical explorations of Mont Blanc, these scientific explorations help us better describe Earth’s biogeochemical evolution–both present and past. Samples of the massif that we bring back from the field like sediment, snow, and ice enable this pursuit. The importance of collecting and studying these materials only grows as global warming accelerates the loss of rich glacial archives and the rate of ecosystem change in the massif.
Written by Kara Sampsell, edited by Lucia Layritz
