Melting glaciers in the Hindu Kush, Karakoram, and Himalaya mountains, combined with record-breaking monsoons, fed extreme flooding this year that killed over a thousand people, created a public health crisis and left a third of the country underwater. Pakistan’s climate change minister tweeted videos of the destruction and blamed “high global temperatures.”
In Nepal, a Himalayan glacier melted in 2021, triggering an avalanche that flooded and devastated the verdant Melamchi River Valley and destroyed a project to deliver tap water to the country’s capital, Kathmandu. It had opened just a few weeks earlier after 50 years of work and hundreds of millions of dollars of financing.
Glaciers are disappearing in the mountain ranges
Nearly 870 million people rely on the glaciers in the Himalayan and Karakoram mountain ranges to modulate the freshwater they use for drinking, irrigating crops, creating electricity, and providing ecosystem services. These massive bodies of ice are known as the “Third Pole” because the volume of ice is likely third to that of the polar regions. They serve as a “water tower,” and some 2 billion people benefit from glaciers in High-mountain Asia altogether. In addition to providing ecosystem services and daily needs, these mountains have tremendous cultural meaning in two of the world’s major religions, Hinduism and Buddhism.
A recent study found 40% of the area of many Himalayan glaciers has disappeared since the Little Ice Age 400 to 700 years ago. Duncan Quincey, Professor of Glaciology at the School of Geography at University of Leeds, and colleagues examined over 14,700 Himalayan glaciers, looking back to the Little Ice Age to reconstruct the glaciers and learn about how they have changed. “It’s important to put the current rates of recession in some sort of long term context,” Quincey says.
They found massively accelerating ice loss, with the authors writing, “The ten-fold acceleration in ice loss we have observed across the Himalaya far exceeds any centennial-scale rates of change that have been recorded elsewhere in the world.”
“I think we can be quite confident that at least within recent history the rates of recession we’re seeing at the moment are beyond precedence,” Quincey says. “There is a clear acceleration in mass loss and the concern there is for how long that can be sustained until there is some sort of threshold reached.”
Since the glaciers act as massive water towers storing vital freshwater, when they shrink less water is available for later, such as times of drought. Typically, the monsoon brings rain, which is then followed by snowmelt in the spring, followed by glacier melt.
“In a normal year, you get quite a lot of spring snow melt coming down,” says British Antarctic Survey glaciologist Hamish Pritchard. “And then as that ran out, the glacier would start contributing to ice melt as well, and that was keeping the rivers flowing.”
The glaciers are especially vital in drought years, and as they melt, less ice storage is available for the future, and people may lose a critical water source.
Melting glaciers can cause deadly flooding
Fast-melting glaciers also create hazards like the flooding that devastated Pakistan this year and wiped out Kathmandu’s tap water project. Glacial-lake outburst floods are a particular concern, as well as run-off floods and debris flows. These onslaughts of water not only cause death and destruction downstream but also destroy hydropower facilities in their path and compromise plans for future electricity development.
“Glaciers have an end moraine, and if the glacier retreats back and it leaves a hollow behind the moraine where the ice was, that can then fill up with water,” Pritchard says. “And the problem is that moraine dam is unstable. It’s just sediment, it’s not consolidated, not bedrock, not concrete. It’s just stones and mud. At some point it will fail mechanically if you’ve got enough force behind it, enough weight of water, and when that goes that can be really sudden, great volumes of water that flow downstream very fast, you have these flash floods hitting communities downstream, very large volumes very rapidly so they can wipe out bridges, and fields, and hydropower plants, and also railways.”
If unconsolidated sediment fails, a deadly flood could result. “You just need a failure of that unconsolidated sediment for there to be a catastrophic outburst flood which can wipe out villages and some of their lands in almost an instant,” Quincey says.
The region is not all melting at the same rate. East Nepal and parts of Bhutan are losing ice at the fastest rates, and a variety of factors come into play, including the albedo effect of glacial surface debris causing the ice to melt faster. While most of the glaciers in the area are losing mass, the Central Karakoram glaciers are changing less, and this is dubbed the “Karakoram anomaly.”
Four river basins in the Himalaya-Karakoram (Brahmaputra, Ganges, Indus, and Tarim) are expected to see “peak water” around 2050, according to a model set to the “moderate” greenhouse gas scenario of RCP4.5. The exercise found that by century’s end, only 32% of Himalayan glacier area (and 74% of the Karakoram glaciers) would remain.
Warming temperatures also mean more rainfall instead of snow, which could lead to additional winter runoff, flooding and a lack of water in the spring when winter snowpack would ordinarily melt. Water shortages, combined with flooding, can exacerbate socioeconomic and geopolitical impacts.
Pritchard, in his 2019 Nature article “Asia’s shrinking glaciers protect large populations from drought stress,” wrote that having summer meltwater available during droughts “reduces the risk of social instability, conflict and sudden migrations triggered by water scarcity, which is already associated with the large, rapidly growing populations and hydro-economies of these basins.”
Additionally, Pritchard notes the snow and ice are culturally important to many in the region, and the appeal of massive glacier-covered mountains also brings tourists to the area.
Protecting people from dangers of melting glaciers
Scientists point to the need for data collection in the area, to monitor and predict what is to come as well as to create a system to warn people downstream of imminent hazards like flooding. In the Nature Reviews Earth & Environment article, Pritchard and colleagues point to the need for a “widespread array of open-data weather stations, river-flow gauges and glacier mass-balance monitoring sites.” Instruments and warning systems could also give a few minutes warning to people downstream of imminent hazards.
“What that could buy you is life saving time to escape from that flash flood,” Pritchard says.
More than anything, what these glaciers need is reducing greenhouse gas emissions. While some have discussed building dams to help take on part of glaciers’ water storage role, Pritchard says that would be very expensive, and would introduce other potential risks, such as dam failure. “Really there aren’t very many good options just to increase water supply,” Pritchard says.
“Ultimately there is no solution that I can imagine that is better than keeping the glaciers there to whatever extent possible which means to avoid those high emissions scenarios because nothing can replace that,” Pritchard says.
Models have shown that 83% of the Karakoram glacier would survive to the end of the century in a RCP 2.6 scenario, along with 52% in the Himalayas. However, a RCP 8.5 scenario would lead to only 16% of the Himalayas remaining and 57% of the Karakoram by then.
Keeping emissions low may help slow the pace of the melting, and also give humans time to adapt and come up with solutions. This is significant on a massive scale.
“These glaciers have been in these environments for centuries, for ice ages on geological time scales and we’re now at a point where we risk seeing them almost disappear before our eyes,” Quincey says. “[Over] the last 10 years I’ve seen the changes on these glaciers year in year out. It’s going to be within the next generation they’ll start to see some of these areas completely devoid of ice cover. … It’s an iconic region of the world and the interplay between people and the environment is acute, direct, and at the moment we stand on the threshold of that ceasing to be the case because people will simply not be able to survive in the places that they’ve been able to previously.”