A trip to Switzerland: looking for glacier basal ice
Article written by Lisa Ardoin, on the 16/06/2022
The focus of my thesis is the gas measurement concentration in a specific section of the ice core: the basal section. One of the specificities of this ice, is the presence of debris (ranging in size from few centimetres to clay) between the ice crystals. These debris make the measurements a bit touchy because most of the analytical techniques used in ice core sciences are specifically designed for ice, clear ice, without particles in it.
To develop an analytical method specific to the basal ice, I needed samples close to the ones from Antarctic ice cores but less precious to test what the best way is to release the gases trapped within the ice crystals and between the debris. This is how we came up with this idea to sample continental glacier basal ice in the Alps.
At that point, I was thinking that it would be an easy and short mission of 2-3 days… I was wrong! When we started to discuss the mission with my supervisors, F. Fripiat and J.L. Tison, they told me that we would need a whole week to prospect different glaciers and then to sample the most interesting ones. We decided to go to Switzerland, in the canton of Valais, where there are rock glaciers.
Map of the glaciers of interest
Then, came the logistic part: the choice of the vehicle, gathering the equipment in duplicate, finding a good accommodation from where we would be able to reach the different glacier valleys, bringing a fridge (and two generators) with us to preserve the samples on the way back to Brussels!
Our racing truck for the week, full of equipment
We left on May 21st, with a 11m3 truck full of material. During the first four days, we went on and on at the different spots: Tsijore Nouve, Moiry, Tsanfleuron, Grubben glaciers. We faced many difficulties in the field. The main one was finding the basal ice layer that is not always present or accessible. And we realised once on site, after 1 to 2 hours of driving in the mountains and a hike of at least 2 hours, that the snow abundance above 2800m high was still hiding the front of two glaciers we were aiming (Tsanfleuron and Gruben glaciers). Also, the road to reach Moiry glacier was closed because of avalanche risk, and it was not possible to bring the truck with the equipment close to the glacier. So, the Tsijore Nouve glacier, the first one we visited, was the only one sampleable.
Front of the rock glacier Gruben
On the two last days of our mission, our fridge and the icepacks were cooled down to -25°C: we were ready for sampling. We came back to Tsijore Nouve glacier and carry the equipment (chainsaw, cool bags full of icepacks to name only the heaviest material) until the spot we noticed few days earlier. We carried the material for 500m up, on 1km-distance, without a path, in the moraines. That was the easy part compared to the way back to the truck when we had a 30kg block of ice to carry in the cool bags off our backs!
The sample site (white arrow) at Tsijore Nouve glacier
We were able to bring 5 blocks of ice for a total amount of about 140kg of ice containing 2 basal ice sequences. A successful mission, rich in emotions and in physical exercises 😊
One of the basal ice blocks just after its extraction
A part of the sampling team, after we cut the last block of ice from back to front: F. Fripiat, L. Ardoin, J.L. Tison