Monitoring Glaciers at the Top of the world

While water is an essential resource for the inhabitants of the Himalays, it also brings its share of risks. Glacier melt, which is accelerating due to global warming, has created new high-altitude lakes and filled up existing ones. In the event of earthquakes and especially landslides, waves can suddenly cause lakes to empty, thereby threatening local populations.

This plane, which usually transports trekkers to Mount Everest, is also how scientists travel to their location of study. Lukla airport, located at an altitude of 2,840 m, is one of the world's most dangerous airports.

The team of scientists needs fifteen days of gradual acclimation in order to work atop the glacier, at an altitude of 6,350 m. Everything must be carried up by humans or yaks. Here they must take this snowy pass, before climbing even higher to take samples and measurements.

Once atop Mera Peak glacier, at an altitude of 6,350 m, Patrick Wagnon drills ice cores to measure the accumulation of snow over the course of the year. The bamboo stalks that were set a few meters in the ground the previous year are now practically buried in snow, and now serve as a marker for collecting samples.

As they do every year, scientists spread blue powder on the surface of the snow cover. A bamboo stalk is driven 2 to 3 meters into the ground and georeferenced in order to mark the spot. It will be partially covered in snow when they return the following year. Here in the southern Himalayas, the height of snow accumulated varies from year to year. No trend is detectable for the moment.

All of this collected data is connected with that gathered by weather stations in various locations. This provides a good view of the climate in this part of the Himalayan Range. In the south, the foothills act as a barrier, and receive much more rain than the mountains to the north. Here ethanol is being poured into a rain gauge to avoid freezing, while oil prevents the evaporation of precipitation.

It is not only possible to study the glaciers of today, but also those of the past. Why did they advance or retreat at certain periods? To this end Vincent Jomelli takes rock samples from moraines, natural piles of rocks that sometimes encircle glacial lakes. Once in the laboratory he analyses the beryllium isotopes formed by cosmic radiation, a good indicator of when the rocks were released by the glacier and exposed to air.

All of these measurements help to better understand the impact of climate change on glaciers, and the risks they pose for local populations. In this highly touristic valley, the village of Dingboche is directly threatened by Imja Tsho Lake. Nepalese authorities partially emptied it in 2016, lowering its level by 3 m. This costly operation took 6 months, and offered greater security to the local population.