Melting danger: A dead glacier is a loss; a dying one a threat
As humans warm the planet, so much ice has been erased from around Mount Everest that the elevation at base camp in Nepal, which sits on a melting glacier, has dropped more than 220 feet since the 1980s
Representative image
The ice of the Himalayas is wasting away. Glacier-draped slopes are going bare. The ground atop the mountain range, which sprawls across five Asian countries, is slumping and sliding as the ice beneath it — ice that held the land together — disappears. Meltwater is puddling in the valleys below, forming deep lakes.
As humans warm the planet, so much ice has been erased from around Mount Everest that the elevation at base camp in Nepal, which sits on a melting glacier, has dropped more than 220 feet since the 1980s.
But this loss is not unfolding gradually.
Often it begins slowly, imperceptibly — and then it happens all at once, with catastrophic consequences for the people below. That was how it went on a warm August day last year.
Thame, a secluded village of 370 people, sits in a valley in the Everest region. Glacial melt had been pooling rapidly in a high spot above the village for more than a decade. The resulting lake was so remote that nobody had given it a name.
On Aug. 16, 2024, rocks from the surrounding mountains fell hundreds of feet into this lake, displacing an enormous amount of water. The water rushed down the valley and into another lake, heaving up more water. Soon, 100 million gallons was coursing downhill. Toward the village.
People in Thame heard a crescendoing roar.
By the time the water raged through, it was as if a swath of the village had never existed. The medical clinic, gone. The school, destroyed. Two dozen homes and trekking lodges, plus fields of potatoes — wiped out.
Months later, a scientist named Scott Watson was walking the flood’s path in reverse, up the steep valleys, up past mud-encrusted books in the ruined school, up to the unknown lake that had suddenly made itself very known.
All across the fast-warming Himalayas, melting glaciers are creating thousands of high-altitude lakes — and thousands of new opportunities for avalanches and earthquakes to cause destruction. When falling rocks or snow land on a frozen glacier, nothing much happens. But as the ice melts and forms a lake, those falling objects can set off a flood that menaces villages, tourist lodges, hydropower plants and anything else in its path.
Watson, a glaciologist at the University of Leeds, and his team trekked through Thame as part of an expedition in the Everest region to measure glacial lakes using sonar and drones.
Sitting on these lakes in an inflatable kayak, the scientists found them anything but placid. Ice cliffs leaked noisy streams of fresh meltwater. Rocks and debris tumbled in. Behind heavy clouds, unseen landslides rumbled all around, like rolling thunder.
The death of a glacier is a loss reversible only on geological time scales. But before a glacier is gone — while it is still dying — it represents a threat.
As a glacier shrinks, it sheds water that gathers in the earthen bowl where the ice once sat, forming a lake. The dirt and rock around this bowl are loose, crumbly. Maybe one day there is a landslide. Maybe a chunk of the glacier’s remaining ice breaks off and plummets into the water.
Picture doing a cannonball into an aboveground swimming pool, said Daniel Shugar, an expert on glacial floods at the University of Calgary — except you blow out an entire wall of the pool. “It would drain within seconds,” he said.
Water plunges down the valley, picking up sand, silt, gravel and boulders. It becomes a slurry so thick that it knocks down buildings.
But it isn’t just their capacity for devastation that makes these floods terrifying. It’s how hard it is to predict where, when and how they will happen.
The lakes that flooded Thame last year were small, not on anybody’s list of those most likely to cause a disaster.
When you think of a glacier, you probably imagine an expanse of white. Watson and his team crossed the face of Nepal’s longest glacier and found a river of dirt, boulders and milky-gray water.
Ice is still there, beneath the debris. But as it melts, puddles become ponds, ponds become lakes, and lakes join up, transforming the landscape into ribbonlike waterways.
One way to reduce flood hazards is by making lakes smaller. Nepal has begun lowering water levels at some high-risk lakes, though melting glaciers continue to feed them.
The New York Times
