A team of British glaciologists spent four weeks on Mount Everest's Khumbu Glacier — the world's highest — collecting data on the surface topography and temperature, and measuring rates of melt. They went looking for small puddles or ponds; what they found instead was a lake.
"We already knew that the surface of the Khumbu Glacier was pitted with supraglacial ponds," says Duncan Quincey, the Leeds University scientist who led the field study team. "And now, we've observed that the ponds on the eastern side of the lower section of the glacier have coalesced into a small lake the size of several football fields."
The Khumbu Glacier is a crucial one on Everest: It stretches for 10 miles on the southwest side of Everest's summit, and mountaineers follow the edge of the glacier on their trek to Everest Base Camp, which sits on the glacier itself. It also includes the Khumbu Icefall — located between Base Camp and Camp 1 — and the site of the 2014 avalanche that killed 16 Sherpa.
The appearance of lakes is worrisome for a number of reasons, including the fact that scientists aren't sure how such large swaths of meltwater pooling on the glacier will affect the villages downstream. "The lakes might act as a natural reservoir storing vital water resources or they might pose a hazard to the people living below, or maybe both," says Quincey.
Then there's the impact of melt on climbers. Mountaineers have recently begun to encounter challenges from glacial meltwater already. In 2014, Alan Arnette diverted his ascent of K2 to deal with a newly formed lake on the Baltoro Glacier. "An ice dam had broken between multiple ponds, creating a large lake," Arnette says. "We had to take a six-hour detour to establish a new route around it."
Furthermore, Quincey and team report that while the upper section of the glacier may not contain such large lakes, it is actually melting the fastest. Using satellite images acquired over the last few decades and a new technique called Structure-from-Motion (SfM), Quincey and team deduced that the section of the Khumbu Glacier at Base Camp was lowering at a rate of around 2 meters, or 6 feet, per year.
As the glacier continues to recede, Quincey and team hypothesize that it will ultimately become disconnected from the Khumbu Icefall, presenting a fresh set of risks and challenges for mountaineers attempting to summit Everest. "We don't know how long that will take," says Quincey. "But what we do know is that right now things are changing fast."
The team will return to Everest in May 2016 for additional data collection.