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Scientists say Himalayan glaciers could provide an unusual respite as temperatures rise

Scientists say Himalayan glaciers could provide an unusual respite as temperatures rise



CNN

Himalayan glaciers are melting fast, but a new report shows that a stunning phenomenon in the world’s highest mountain range could help slow the effects of the global climate crisis.

When high temperatures reach certain glaciers at high altitudes, it triggers a startle response that sends strong, cold winds blowing down the slopes, according to the study published Dec. 4 in the journal. Natural earth sciences.

Francesca Pellicciotti, professor of glaciology at the Institute of Science and Technology in Austria and lead author of the study, explained that a warming climate creates a larger temperature gap between the ambient air above the glaciers in the Himalayas and the cold air that is in direct contact with the surface of the glaciers. .

“This leads to an increase in turbulent heat exchange at the glacier surface and a stronger cooling of the surface air mass,” she said in a press release.

As cold, dry surface air becomes colder and denser, it sinks. Air mass flows down slopes into valleys, causing a cooling effect in the lower regions of glaciers and adjacent ecosystems.

With ice and snow from the mountain range fed by 12 rivers providing fresh water to nearly 2 billion people in 16 countries, it is important to know whether Himalayan glaciers can maintain a conservative cooling effect on themselves while the region faces potential warming. temperatures over the next few decades.

Salerno/Guignon/Pellicciotti/Natural Earth Sciences

A diagram of air cooling in regions around Himalayan glaciers as they interact with global warming.

June report Previously covered by CNN It showed that Himalayan glaciers melted 65% faster in the 2000s than in the previous decade, suggesting that rising temperatures are already having an impact in the region.

“The main effect of rising temperature on glaciers is increased ice loss due to increased melting,” said Fanny Brun, a research scientist at the Institute of Environmental Sciences in Grenoble, France. She did not participate in the study.

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“The underlying mechanisms are lengthening and intensifying the melt season. They cause glaciers to thin and retreat, degrading landscapes that tend to increase in air temperature (because) “The surface absorbs more energy,” Brun said.

Franco Salerno/Institute of Science and Technology Austria

Scientists are pictured here discussing findings during a field trip. From left to right: Nicola Guignon (IRSA-CNR), Francesca Bellicciotti (ISTA) and Thomas Shaw (ISTA).

The energy absorption on the surface is determined by something called Whiteness effect. Light or “white” surfaces such as clean snow and ice will reflect more sunlight (high albedo) than “dark” surfaces such as exposed land with retreating glaciers, soil, and oceans (low albedo). In general, Bron said this phenomenon is explained as Positive feedback loopor a process that promotes change, but is generally not well studied and difficult to quantify.

However, at the base of Mount Everest, overall average temperature measurements seemed strangely stable rather than increasing. Careful analysis of the data revealed what was really happening.

“While minimum temperatures have been steadily rising, maximum surface temperatures in summer have been steadily falling,” said Franco Salerno, co-author of the report and a researcher at Italy’s National Research Council, or CNR.

However, even the presence of these cold winds is not enough to fully counter the increasing temperatures and melting of glaciers due to climate change. Why these glaciers are melting so quickly is complex, said Thomas Shaw, part of the ISTA research group with Pellicciotti.

“The cooling is local, but it may still not be enough to overcome the larger impact of global warming and fully preserve the glaciers,” Xu said.

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Pelliciotti explained that the general scarcity of data in high-altitude regions around the world is what led the study team to focus on using unique ground observation records at a single station in the Himalayas.

“The process we highlight in the paper is potentially of global importance and could occur on any glacier around the world where the conditions are met,” she said.

Pelliciotti said the new study provides a compelling case to collect more long-term, high-altitude data that is much needed to prove the new findings and their broader implications.

The Pyramid International Observatory/Climate Station is located at a glacier elevation of 5,050 meters (16,568 ft), along the southern slopes of Mount Everest. The observatory has recorded detailed meteorological data for nearly 30 years.

It’s these granular meteorological observations that Pellicciotti, Salerno and a team of researchers used to conclude that high temperatures lead to so-called katabatic winds.

Cold winds, caused by air flowing downhill, usually occur in mountainous regions, including the Himalayas.

Franco Salerno/Institute of Science and Technology Austria

The International Pyramid Laboratory/Climate Observatory Station on Mount Everest has been recording hourly meteorological data for nearly three decades.

“Katabatic winds are a common feature of Himalayan glaciers and valleys, and have probably always occurred,” Pelliciotti said. “But what we observe is a significant increase in the intensity and duration of katabatic winds, and this is due to the fact that ambient air temperatures have risen in a warming world.”

Another thing the team noticed was that ground-level ozone concentrations rose in relation to lower temperatures. This evidence shows that katabatic winds act as a pump capable of transporting cold air from higher altitudes and layers of the atmosphere down to the valley, Pelliciotti explained.

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“According to the current state of knowledge, Himalayan glaciers are doing slightly better than average glaciers in terms of mass losses,” Brun said.

In the central Himalayas, glaciers have thinned by about 9 meters (29.5 feet) over the past two decades, Brun explained.

“This is much lower than the glaciers in Europe, which have diminished “It is about 20 meters (65.6 feet) in size over the same time period, but this is larger than in other areas in Asia (for example in the Karakoram region), or in the Arctic region,” Brun said.

Understanding how well these glaciers can locally counteract the effects of global warming may be crucial to effectively addressing our changing world.

“We believe that katabatic winds are a healthy response of glaciers to rising global temperatures, and that this phenomenon could help preserve the permafrost and surrounding vegetation,” said study co-author Nicolas Guignon, a researcher at the National Research Council in Italy.

However, further analysis is needed. The study team then aims to determine which ice properties favor the cooling effect. More long-term ground stations to test this hypothesis elsewhere are virtually absent, Pelliciotti said.

“Even if glaciers cannot sustain themselves forever, they may sustain their surrounding environment for some time,” she said. “Therefore, we call for more interdisciplinary research approaches to unify efforts toward explaining the effects of global warming.”

a Separate report in 2019 He found that even in the most optimistic case, where average global warming is limited to just 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial temperatures, the Himalayan region would lose at least a third of its glaciers.