Climate change has arrived decisively on the roof of the world on Mount Everest: the highest glacier on Earth’s highest mountain is losing decades of ice every year, according to a new study by researchers who have extracted a glacier ice core.
The study, published in the Nature Portfolio Journal Climate and atmospheric research, found that Mount Everest’s South Col glacier, which climbers cross to reach the summit, may have lost half its mass since the 1990s due to warming temperatures in the region. It could disappear entirely by the middle of this century.
The findings result from the 2019 National Geographic and Rolex Perpetual Planet Everest Expedition, which brought together 34 international and Nepalese scientists, several Sherpas and a series of logistical challenges.
The expedition was extensive and, in addition to the ice core, included collecting biological samples, creating a high-resolution map, and studying water quality and the history of Everest glaciers, said expedition leader and senior scientist Paul Mayewski. National geographic. The team also installed five weather stations (including two at the highest altitudes in the world for weather stations).
âIt was the most comprehensive scientific experiment ever conducted on the southern slope of Everest,â says Mayewski.
According to mountaineer Ryan Waters, who has summited Everest six times but did not participate in this study, the South Col Glacier offers an awe-inspiring view for climbers approaching the final stage of their ascent. âYou quickly admire the huge snow and ice from the glacier pouring down from Everest above the high camp,â he says.
This was one of the highlights of the expedition as mountain glaciers around the world rapidly declining due to climate change. But, says Mayewski, a glaciologist who is director of the Climate Change Institute at the University of Maine, there is relatively little information on glaciers at the highest elevations.
“And one of the questions was, when you go that high, obviously it’s a lot colder. So the Everest glaciers, even at 8,000 meters (26,250 feet), where South Col is , do they retreat?
Coring of the highest glacier
A key part of the research involved extracting a cylindrical piece of ice from the glacier, more than 1,000 meters (3,200 feet) higher than the previous tallest ice core ever collected. This involved adapting existing drilling equipment to be as light as possible so that it could be carried by hand up the mountain and operated in the air. Although the team conducted trials in extreme cold conditions in Maine, Iceland and the Himalayas, there was no guarantee that the equipment would work when it was needed most.
âIt was a lot of stress, actually,â says Mariusz Potocki, a glaciochemist and PhD student at the University of Maine who collected the carrot. “It was such a relief when it worked.”
The results, however, shocked Potocki and the team. When the 10-meter (33-foot) ice core was analyzed, radiocarbon dating revealed that the ice on the surface was around 2,000 years old. In other words, any ice that had settled on the glacier over the past two millennia had simply disappeared. The core contained layers of annual growth of ice – much like tree rings – and by measuring their thickness the team calculated that, assuming the rate of ice deposition remained the same over time , approximately 55 meters (180 feet) of ice was lost.
Based on measurements of warming and ice loss elsewhere in the Himalayas, the researchers infer that most of this loss has occurred since the 1990s. If this rate of ice loss continues, Mayewski says , the South Col glacier âwill probably disappear within a few decades. It’s a pretty remarkable transition.
While the magnitude of the change surprised scientists, it mirrors what climbers like Waters have noticed for years, not just on the South Col Glacier, but across the Himalayas.
“I have noticed since I first went to the Himalayas 20 years ago that many of the glaciers in and around the Everest region have changed a lot,” Waters says. “The Khumbu Icefall has also changed a lot over those years, so it’s not just the tallest of the glaciers, but apparently all of them.
How’s it going ?
The researchers say ice loss is likely greatly accelerated by a process called sublimation, in which snow and ice evaporate without passing through a liquid-water phase. Sublimation is common in cold, dry climates, particularly at high altitudes, but which experience plenty of sunshine and strong winds – all the boxes ticked by the South Face of Everest. And it’s exacerbated on the South Col Glacier, Potocki says, by an almost complete loss of snow cover on the glacier’s surface.
The snow has a top albedo– that is, it reflects most of the solar radiation back into the atmosphere. âIf you lose fresh snow, the ice itself is darker and just absorbs more solar radiation, so the melting and sublimation seem more intense and the ice loss increases,â he says.
âMariusz and I drill ice cores all over the world, and we developed the drilling equipment for this expedition knowing that it would probably end up drilling in snow and then in ice,â Mayewski explains. “It was a real shock to see this exposed ice surface.”
For Mayewski, the findings add to a growing catalog of evidence that climate change is now fundamentally altering even the most remote regions of the world.
âWe know the oceans are polluted, we know they are warming and acidifying,â he says. âWe know that there are times, even in the middle of winter, when warm air masses reach the North Pole and temperatures there exceed freezing. We know that there are certain times in the summer when the entire surface of the Greenland ice sheet melts.
âAnd now we have proof that even the tallest glacier on the world’s tallest mountain is rapidly losing its ice. So yes, this is a real wake-up call.