As soon as the sun sets in the Himalayas and the temperature drops, an eerie noise is heard in the depths of the glaciers around Everest.
Researchers led by glaciologist Yevgeny Podolsky found that the sounds of breaking and fragmenting high-altitude glaciers are caused by a sharp drop in temperature after dark, which causes the ice to crack.
The team determined the cause of the sounds in 2018 after spending more than a week trekking through the Nepalese Himalayas to test for seismic activity in the Trakarding-Trumbau glacier system.
Dr. Podolsky and his team spent three weeks shivering on the glacier, not knowing what caused the night sounds, but confirmed they were due to extreme cold when they returned to sea level and checked the seismograph data.
Their study was the first to show such a large amount of seismic activity due to a thermal break in the ice, based on a wide range of studies on the behavior of glaciers as the effects of climate change constantly warm the planet.
Dave Hahn, an expedition leader who has completed 15 races on the summit of Everest, said that at night when he and his fellow climbers were resting, he heard strange sounds, including “falling ice and rocks in various places in the valley.”
“It’s hard to sleep,” he added.
When Dr. Podolsky and his team traveled to the Nepalese Himalayas to test the seismic activity of the Truckarding-Trumbau glaciers, they landed about three miles above sea level, within sight of Mount Everest, which is about 29,000 feet high.
“It was a great experience because it’s a great area to work in. I mostly dine while looking at Everest,” said Dr. Podolsky, who works at the Center for Arctic Studies at Hokkaido University in Japan.
During the day, Dr. Podolsky and his team can work comfortably in shirts.
But as night falls, temperatures can drop to around -15 degrees Celsius or 5 degrees Fahrenheit.
After dark, he and his team heard “that noisy explosion,” adding, “We noticed our glacier cracking or tearing at night.”
The team placed sensors on the ice to measure vibrations deep in the glacier, using the same method used to measure the magnitude of earthquakes.
The researchers collected seismic vibration data and compared it with temperature and wind data, which helped establish a strong link between temperature fluctuations and nighttime noise.
“The local ice has been shown to be very sensitive to such a high rate of change,” Dr. Podolsky and colleagues write in Geophysical Research Letters.
The study could help more teams of glaciologists and climate experts better understand the behavior of glaciers in remote regions, such as deep in the Himalayas, where one of the largest ice storage sites on Earth is located.
The Himalayan glaciers are melting at a devastating rate, putting millions of people and the economies of South Asia at risk. The region’s massive ice sheets have been shrinking 10 times faster in the last four decades than in the previous seven centuries.
A 2021 study published in the journal Scientific Reports found that Himalayan glaciers have lost about 40% of their area over the past hundreds of years, or 390 to 586 cubic kilometers of ice – enough to raise global sea levels from 0.92 to 1. 38 mm.
Source: Daily Mail
