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- Climate scientists observed a peculiar cooling trend in Himalayan glaciers 10 years ago.
- They now think the trend may be the result of intensifying winds that can reach over 100 mph.
- Mountaineers can't catch a break as climate change makes the mountains increasingly more dangerous.
As climate change drives up global average temperatures, glaciers around the world's tallest mountains are actually getting slightly colder during the warm season, according to new research published in the peer-reviewed journal Nature Geoscience.
Located on the southern face of Mount Everest along the Khumbu Valley about 3.1 miles above sea level, sits one of the world's few high-elevation science labs, called the Pyramid International Observatory.
It's been collecting hourly data on measurements like the mountain's air temperature, total precipitation, humidity, and wind speed since the early '90s. With nearly four decades of data in hand, scientists saw a strange pattern.
They found that the maximum daytime temperature during the warmer months from May to October had decreased by around 0.040 °C per year over the last 15 years.
Was it a mistake? The researchers cross-checked the data with other weather stations around the southernmost stations of the Tibetan plateau. They realized that the cooling trend wasn't just limited to the glaciers around Mt. Everest; it was across the entire Himalayas.
But how could this be? After all, a report published last year found that Himalayan glaciers melted faster between 2010 and 2019 than in the previous decade, suggesting the glaciers were getting warmer along with the rest of the world.
Blame the wind
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Researchers think that this cooling trend is the result of a well-understood phenomenon called katabatic winds.
On warm days, as sunlight heats the glaciers, the air just above the glacier's surface warms and rises. This creates a vacuum causing the cold air around the snowy peaks to rush down due to gravity.
As the phenomenon intensifies, it creates local katabatic winds which typically peak in the afternoon and can reach speeds of over 100 mph.
As average global temperatures rise worldwide, due to climate change, katabatic winds are growing more intense because the more heat that's warming and rising from the mountain's surface, the more it forces cold air down. That's what's causing the cooling trend over the last 15 years, the researchers reported.
Moreover, the researchers think the chilly winds may have partly helped in slowing the melting of these glaciers which otherwise could have been even worse.
But there is a catch.
The study also found that the lowest nighttime temperature during cold months (November to April) is on the rise. As the coldest nights are becoming less cold and warm month days are getting mildly cooler, the average temperature tends to balance out, giving a deceiving impression of the temperature trend.
That said, glaciers will continue to melt in the face of climate change because glacial melting is not just linked to air temperature close to the ice.
Glaciers will continue to melt as global temperatures rise
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Ice can act like a buffer, absorbing some heat before increasing in temperature.
During the warm daylight hours, the glacier ice absorbs heat from the surrounding air. Then at night, the ice releases some of that stored heat energy, preventing the air temperature from dropping too low.
So the ice damps down the daily heat peaks and cold dips in the area right around the glacier.
That's why temperatures farther away from the glacier better reflect the true daily peaks and nighttime cooling which ends up influencing the melting processes.
"Understanding this whole process was a great relief," said Franco Salerno, lead author of the paper and an environmental scientist at the National Research Council, Institute of Polar Sciences, Milan.
His team had noticed the decreasing temperature trend in warmer months nearly 10 years ago but couldn't pin down the exact phenomenon. Now, more studies can focus on this local weather phenomenon.
Most importantly, the finding shows the role of glaciers in shaping local mountain climates. And that has had a huge impact on climbers.
Rising risks for businesses
Lhakpa Sherpa
The frigid, dense, high-speed katabatic winds can easily intensify — even reaching hurricane speed. As a result, these winds have a big impact on the local weather of the mountain.
As a result "climbing has become much trickier as our guides have to asses the route to the summit in each trip," said Gordon Janow, director of the mountain climbing guide service Alpine Ascents, who has been in the mountaineering industry for nearly four decades.
The terrain has also gotten more technical as melting glaciers open up huge crevasses.
"We have to go 100 yards to the right then cut back to the left then cut to the right," he said.
What was once a 10-hour journey to the summit can extend to 12 or even 14 hours. "Then, all of a sudden we may come across a glacier that we can't cross," Janow added. As a result, many mountains are not even climbed anymore.
The melting of glaciers triggered by such local weather phenomena has brought trouble to not only the Himalayas but mountains all over the world.
Mount Rainier, for example, has traditionally served as a training ground for many mountaineers. "I have had people come in saying things like, 'My grandfather climbed Mount Rainier by himself in 1957. We're gonna do it.'," he said.
"But people fail to realize it's not your grandfather's mountain anymore," he said.