What are mountain glaciers and why do they matter?

When a social media post about the rapid loss of glacial ice went viral, it highlighted people's shock over the impact of global heating on cherished landscapes.

The post on X by Duncan Porter, an environmentalist from Bristol in England, pictured him with his wife at Rhone glacier in Switzerland. It was 15 years since they had been photographed in the same location. The severe loss of ice in that time profoundly affected him.

"Not gonna lie, it made me cry," he wrote in a post on X.

And he is not the only one who cares. 

Mourning disappearing glaciers 

Glaciers are epic ice-flows that have carved out mountains and valleys over millennia — the oldest in South Africa dates back 2.9 billion years.  

But these ancient forces of nature, which hold enough fresh water for around two billion people, are melting. At least half of the world's mountain glaciers are likely to disappear by 2100 as the world heats up due to climate change.  

Cold climate cultures are struggling to deal with this loss.In 2019, a funeral ceremony was held at Iceland's Okjökull Glacier, said to be the first lost to global heating. 

Mourners unveiled a plaque announcing that all the country's main glaciers are expected to follow in the next 200 years.

While there is a cultural attachment to mountains and their "multitude of different ecosystems," glaciers make these landscapes "unique in people's imagination," noted Giovanni Baccolo, a glaciology expert at theen University of Milano-Bicocca in Italy. He also posts photos in social media comparing glaciers of today to a century ago.

"Glaciers are literally another world," he added of vast ice crystals which, based on a single mineral, are classified as a rock. "[They are] icons of mountains." 

Once these ice caps melt, future generations will not draw alpine mountains "with a white hat," he added.

How glaciers are formed — and give life

The glaciation process begins as snow accumulates and turns to ice, which then expands as annual snowfall outweighs summer melting. 

Mountain glaciers around the globe accumulated massively during ice ages. They moved downhill under their own weight and cut out towering canyons like those found in the Yosemite Valley in California or the New Zealand alps. 

As the world's 200,000-odd mountain glaciers thaw during the warmer months, they release fresh water into rivers and tributaries that sustain crops, communities and ecosystems for around  25% of the world's population. 

But while glaciers have served as water resources for hundreds of years, this can only continue as long as the meltwater is replenished every winter by enough new snow.  And in most areas, thats no longer the case.

Now that many of these gigantic "water towers" are receding in the face of global heating, drought comes fast to the regions that rely on them. This includes South America, where some glaciers in the Andes stretching across Bolivia and Peru and have declined over 50% of their mass since the 1980s. The result is permanent water scarcity for agriculture and human settlements. 

There are anomalies, however. In the Karakoram Range bordering Pakistan, India, Afghanistan and through to China, some glaciers have slowly expanded in recent decades. Experts say this is due to unique regional weather patterns – and that a warming climate will also catch up to the Karakoram, which contains some of the world's tallest mountain peaks.

An accelerated meltdown of mountain glaciers

In the European Alps, glaciers are receding much faster than they can accumulate, say researchers.

In the skiing haven of Switzerland, glaciers lost a record 10% of their volume in just two years between 2022 and 2023. The two-year loss was equivalent to 30 years of retreat between 1960 and 1990. Previously, a 2% retreat in one year was described as "extreme." 

Such rapid glacial decline was blamed on extreme heat, reduced snow and a protracted summer melt, with 2022 the hottest year on record in Europe. 2023 and 2024 have continued the trend, with both likely to be the world's warmest ever.

Studies have shown that anthropomorphic climate change is the "biggest cause" of accelerated glacial retreat.  

At current rates, vast glaciers in the Swiss Alps like Morteratsch, which dates back to the start of the Little Ice Age around 750 years ago, will lose over 70% of its volume within 40 years.

Glaciers cannot grow when they lose their protective snow cover that reflects the sun. Instead, the ice melts even faster.

Can the 'icons of the mountains' be saved?

Some are determined to save what is left. Swiss glaciologist Felix Keller and his engineering team have created a cabling system that can recycle glacial melt water to create a reflective snow layer that can protect Morteratsch Glacier.

"I have tried to do something. I want to be part of the solution and not the problem," said Keller in the documentary film, "Saving Glaciers." 

Other researchers are also looking into methods to slowing down melting. Some ski resorts have begun to use reflective tarpaulins, also called geotextile, to protect the ice from melting in the summer, with mixed results. 

And the huge problem is scaleability. The Swiss Aletsch glacier for instace covers some 78 square kilometers of mountain territory. And the melting ice of Jostedalsbreen in Norway, Europe's largest glacier, is spread across more than 500 square kilometers. While putting a blanket over a small area might work to reflect enough sunlight to protect a small portion of a glacier, but covering the rugged surface of a whole glacier would be very hard to do and quite expensive. 

In a study that looked at efforts to combat glacier melting in the Alps, the researchers concluded that it would be far too costly to protet the world's more than 250,000 square kilometers of mountain glaciers with such methods.  

Meanwhile in the Himalayas of India, so-called ice stupas —a large cone of ice that looks vaguely like Buddhist ceremonial burial mounds called stupas — have been developed by redirecting water from high-altitude streams down to valley communities and refreezing it. 

The technique has since been adopted in Kyrgyzstan, Chile, Mongolia and other countries where they have helped villages cope with water scarcity caused by glacial retreat.  

But scientists say that as the world warms, these artificial mini-glaciers will ultimately suffer the same fate as their huge natural cousins and melt.

The only long-term solution will be to slash the greenhouse gas emissions that fuel climate change.

Nonetheless, if humanity can limit global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) — a best-case scenario — half of our existing glaciers are still expected to disappear by century's end.