Italy was dealing with a prolonged heat wave before a huge chunk of an Alpine glacier broke off and killed hikers on Sunday, and experts say climate change will make such hot, destabilizing conditions more common.
Seven hikers died and several others are missing after large chunks of ice and rock from the Marmolada Glacier hurtled down the mountain in an avalanche. Warmer temperatures combined with below-average winter snowfall were among the factors that may have triggered the event, experts said.
The exact role of climate change in specific events is complex, and large chunks of ice can break off Alpine glaciers naturally. But climate change is fueling higher temperatures that may lead to more melting of ice and snow, said Brian Menounos, a professor at the University of Northern British Columbia who researches climate change and glaciers.
“Glaciers are responding directly to a warmer climate, a warmer planet,” Menounos said. “They can respond to long-term changes, but they can also respond to these extreme events,” like heat waves.
The Marmolada Glacier is located in the Dolomite Mountains, a series of steep, dramatic peaks in northeastern Italy. The area is already being altered by climate change. Between the late 19th and early 21st centuries, temperatures in the Alps rose twice as fast as the global average, according to Copernicus, the European climate modeling team. The UN has identified the Mediterranean basin that includes Italy as a climate change hotspot prone to heat waves. Glaciers are retreating across Italy, the Alps and around the world.
The government’s National Research Council said the Marmolada glacier has been shrinking for decades and could disappear in 25 to 30 years.
Before the avalanche, daytime temperatures at the glacier elevation were around 50F (10C) when they usually don’t rise much above freezing. The prolonged hot season at high altitudes created a special set of conditions, said Tobias Bolch, who researches glaciers at the University of St. Andrews in Scotland.
Guglielmina Adele Diolaiuti, a professor at the University of Milan who studies glaciers, said images of the ice that remains part of the glacier tell a story of what might have happened.
The upper two-thirds of the ice surface appears slightly dirty, indicating that it was exposed to air.
“It is clear that this section of vertical ice rock was the inner part of a crack,” he said. A crevasse is a deep opening in a glacier.
The bottom is bluer, indicating it was stuck, Diolaiuti said.
Water may have accumulated in the crevasse, adding weight and pressure to the glacier. It may also have loosened the glacier’s grip on the sheer rock it was sitting on, experts said.
Anyone who has tried to shovel ice off a cold road knows that it sticks to the pavement, said Richard Alley, a Penn State professor who studies sheets of ice. But when the weather warms, the ice loosens.
“All of a sudden, oh, you can take it off,” Alley said.
A local official said the damaged section was estimated to be 220 yards (200 meters) wide, 85 yards (80 meters) high and 65 yards (60 meters) deep. It hurtled down the mountain at nearly 200 miles per hour (300 km/h).
The hikers were probably taken completely by surprise.
In addition to the heat, there was below normal snowfall this winter. Northern Italy is struggling with its worst drought in 70 years. When there is less snow, the ice is exposed and impurities can collect on the surface of the glacier, turning the surface a darker color that traps more heat. The extra heat melts ice and snow faster, said Bolch of St. Andrews.
On Tuesday, rescue efforts recovered equipment and body parts. After rain made the rescue difficult on Monday, the sun reappeared on Tuesday.
According to Daniel Farinotti, professor of glaciology at ETH Zurich and WSL Birmensdorf in Switzerland, climate change may reduce the risk of some avalanches. Glaciers need cold weather and snowfall to grow. If glaciers grow on a steep slope, ice pushed over ledges can break off and trigger avalanches. But as temperatures rise, glaciers are retreating and smaller glaciers pose fewer risks, he said.
In the case of Sunday’s avalanche, melting ice and snow is the likely culprit, experts said.
“Ice, snow, are very sensitive to temperature increases, so we expect these types of events to increase in frequency and intensity in the future,” said Roberta Paranuzio, who researches climate change at Italy’s National Research Council. .
While some avalanches occur in isolated areas, the area around the Marmolada Glacier is popular with hikers.
“The very warm weather was one of the reasons why the event happened, but on the other hand, this very warm weather made it attractive for climbers to climb it,” Bolch said.
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