How permafrost thaw triggered by global warming is damaging the Himalayas
Mt Everest Credit: File

It is late April 2022. At Namche Bazaar, a town in the Everest region of Nepal at an elevation of 3555 metres above sea level (m a.s.l), life, and business have not been the same since the COVID-19 outbreak. Located on the way to the Everest south base camp, this bustling market has seen reduced footfall because of the pandemic.

  • Permafrost thaw, one of the changes to the mountain cryosphere in the Himalayas, triggered by global warming is causing irreparable loss and damage to the valley.
  • Considered the largest terrestrial carbon sink on Earth, an estimate suggests that currently, permafrost is a reservoir of up to 1600 billion tons of carbon – that’s more than what the world’s soils store.
  • Scientists fear that the IPCC recommendation of limiting global warming to 1.5 degrees Celsius may not be enough to stop the permafrost from thawing.

Setbacks are not new to the residents of Namche Bazaar; however, the last two years seemed worse, admitted Dilkumari Rai from the Solu region of the Solukhumbu district, who runs a small Nepalese and Chinese eatery. “The business is not profitable,” she said. The pandemic has added to the effects of constantly changing weather that worry the local communities. Avalanches, landslides, and unseasonal rains are becoming terrifyingly frequent.

The local people point to the mountains cast in sombre brown. “These mountains used to be white with snow at this time; they have only a few streaks of snow now. Last year, we had unnaturally heavy snowfall in winter. Summers are a lot warmer now,” said Kapindra Rai, a programme officer at Sagarmatha Pollution Control Committee, a non-profit that manages waste in the Everest region.

Warm winters, warmer summers, landslides, avalanches, and GLOFs (glacier lake outburst flood) — the Himalayan region is increasingly witnessing the vagaries of global warming. At its mildest, it manifests as irregular rains or snowfall, warmer winters, etc., but the valley residents live in constant fear of things escalating any day.

The year 2013 saw the devastating Kedarnath floods on the Indian side of the Himalayas, followed by back-to-back avalanches on Mount Everest in 2014 and 2015. In 2021, 72 people were killed and over 200 went missing in flash floods in India’s Chamoli district of Uttarakhand. In the same year, the Melamchi river overflow and flooding in the Sindhupalchowk district of Nepal killed over 20 people. Over 100 homes were washed away and 400 households displaced; six highway bridges and 12 suspension footbridges were swept away.

An avalanche rescue operation. Avalanches and landslides are increasing in the Himalayan mountains. Photo by Press Information Bureau/ Wikimedia Commons.

Chamoli and Melamchi disasters are “cascading hazards” — a primary trigger such as heavy rainfall, seismic activity like an earthquake, or unexpected snow melting, followed by a web of consequences that cause subsequent hazards influenced by a mix of preconditions and vulnerabilities. High Mountain Asia, researchers say, is highly vulnerable to these cascading hazards. They are now looking into the role of permafrost and its slow thawing under the influence of global warming in triggering disasters like Chamoli and Melamchi.

Permafrost or permanently frozen ground is defined as the ground (soil or rock and the included ice and organic material) that remains at or below zero degrees Celsius for at least two consecutive years.

In the Himalayas, permafrost is “discontinuous” and is found at an elevation of (and above) 4000 m a.s.l, and in warmer places, it is located above 6000 m a.s.l. “Compound extreme events, such as the Chamoli disaster in India and Melamchi disaster in Nepal in 2021, could be potentially linked to permafrost thawing,” said Prashant Baral, a permafrost research consultant at The International Centre for Integrated Mountain Development (ICIMOD) in Nepal.

John Mohd Wani, a researcher who studies permafrost in the Western Himalayan Region, said that preliminary investigation into the Chamoli disaster showed a temperature increase between 2012 and 2016 in the region that warmed at least 40 metres below the ground over four years.

“This most likely thawed permafrost in the region, which led to the event along with other processes such as precipitation increase. Chamoli disaster is a combination of complex processes involving local geology, snow, glacier, permafrost processes and recent warming of the local climate,” he said.

Some of the other impacts of permafrost thawing include changed frequency and unexpected location of landslides and changes to vegetation, run-off patterns, and water quality.

Permafrost, a carbon sink larger than Earth’s soils

Permafrost is overlain by a layer of seasonally frozen and thawing ground known as “the active layer”. Under the active layer, permafrost can be from three feet to 4,900 feet thick. It stores carbon-based remains of plants and animals that froze before they could decompose. For example, one million square kilometres of Siberia, Canada, and Alaska contain pockets of Yedoma — thick deposits of permafrost from the last ice age, reports Nature.

Yedoma contains 130 billion tonnes of organic carbon — the equivalent of more than a decade of global human greenhouse-gas emissions and these deposits are 90 percent ice, making them extremely vulnerable to warming.

Infographic by Labonie Roy/Mongabay.

Scientists estimate that the world’s permafrost holds 1,600 billion tons of carbon, almost double the amount of carbon that is currently in the atmosphere. Oceans and soils, considered Earth’s large carbon reservoirs store up to 40,000 billion tons and 1500 billion tons of carbon followed by vegetation that stores up to 650 billion tons of carbon, making permafrost one of the largest terrestrial carbon sinks on Earth. Its thawing, hence, could release more planet-heating carbon than any other emissions in the world.

During and after a heatwave in 2020 in Siberia, climate scientists warned that warming temperatures are releasing a massive amount of methane, a more potent greenhouse gas than carbon.

ICIMOD in its Hindu Kush Himalaya Assessment Report in 2019 said that even if global warming is kept to 1.5 degrees Celsius as per the IPCC recommendation, warming in the Hindu Kush Himalayan (HKH) region will likely be at least 0.3 degrees Celsius higher. This means that 1.5 degrees Celsius warming in the rest of the world translates to an estimated 1.8 degrees Celsius rise in temperature across the region and up to 2.2 degrees Celsius in the mountains. The report revealed that for the past five to six decades, extreme warm events have been increasing while extreme cold events have been declining in the region.

Permafrost and glacier distribution in the HKH. In this map (above) the permafrost probability map (Obu and others, 2019) is used for indicating permafrost probability distribution and the Randolph Glacier Inventory 6.0 (RGI, 2017) is used for indicating glacier distribution. The graph (below) shows percent-wise distribution of permafrost and glacier in different elevation ranges in the HKH.

“The number of cold nights reduced by one night per decade and the number of cold days reduced by 0.5 days per decade, while the number of warm nights increased by 1.7 nights per decade and the number of warm days increased by 1.2 days per decade,” the report said.

“Permafrost responds directly to global warming; even the mildest variation matters,” Simon Keith Allen, senior scientist, Institute for Environmental Sciences at University of Geneva who studied permafrost in the Indian Himalayas in 2015 told Mongabay-India. “It extends to huge depths beneath the surface. This means that near the surface (top 10 metres or so) the permafrost is thawing very quickly in response to global warming, a reason why we can see small rockfalls occurring immediately during a hot summer, for example. However, it takes much longer (even hundreds of years) for permafrost deep in the ground to slowly respond to global warming.”

“So, even if we limit global warming to 1.5 degrees, deep inside the mountains, it will continue to thaw over many hundreds of years. So large rock avalanches (like what happened in Chamoli) potentially linked to thawing permafrost are a long-term problem and need to be considered under risk assessment strategies for infrastructure in the Himalayas,” he said.

Economic loss and damage to lives and livelihoods

Permafrost thawing can result in huge economic loss in the Himalayan region since the cryosphere lies at the source of many rivers in South Asia and influences a variety of activities from irrigation and fisheries to hydropower, apart from taking care of the water needs of people.

Prashant Baral said permafrost degradation is responsible for substantial changes in regional and continental hydrological systems. “In Tibetan Plateau, there is evidence that permafrost thawing has induced changes in wetlands, ponds, groundwater storage, and vegetation,” he said.

It destabilises slopes triggering landslides. “Some of our roads like Khardung La Pass and Chang La Pass in the Ladakh region pass through higher elevations permafrost zones. In this region, I can say that the permafrost degradation in the ground below the road poses a significant engineering challenge in maintaining these roads,” said John Mohd Wani.

Permafrost thaw can lead to GLOFs, like the one that happened in Gya in Ladakh in September 2014, since most of these lakes are found at elevations where permafrost can exist. In Pakistan, destabilising rock glaciers located in regions with warming permafrost are found responsible for blocking or diverting mountain rivers thus resulting in outburst floods, said Baral.

Pangong glacial lake, Ladakh. Permafrost degradation is responsible for substantial changes in hydrological systems. Photo by Wajahat Iqbal/ Wikimedia Commons.

Moreover, he said, studies say if global mean annual temperatures are 1.9-3.6 degrees Celsius warmer than today, “about 60% of alpine permafrost could thaw, releasing about 85 petagrams of thawed carbon into the atmosphere. That is more than two times the water Three Gorges Dam, considered the world’s largest dam on the Yangtze river in China, can hold.”

At the rate at which permafrost is thawing, as some of the studies suggest. and global warming being its main driver, is the IPCC recommendation of limiting global warming to 1.5 degrees Celsius enough?

A 2021 paper suggests a 1.5 degrees Celsius rise would affect about 18% of permafrost area (an area the same size as India) distributed in the Northern Hemisphere under the Representative Concentration Pathway (RCP) 4.5, a moderate emission scenario that limits global warming to 2-3 degrees Celsius by 2100.

The RCPs are the IPCC’s greenhouse gas emissions trajectories that predict human behaviour to understand how climate may change in the future. The paper states that additional degradation of permafrost area distributed in the Northern Hemisphere is likely under global warming of 1.5 degrees Celsius if we don’t make concerted efforts to cut greenhouse gas emissions (RCP8.5).

“Based on this evidence, it is unlikely that the IPCC recommendation of keeping the temperature below 1.5°C would be enough to let the permafrost areas remain intact,” said Baral.

Drivers of permafrost thawing and mitigation measures to be adopted

While global warming remains the primary driver of permafrost thawing, changes in air temperature, snow cover, vegetation, rainfall and soil moisture, and environmental disturbances (eg. wildfire, human activities like building infrastructure, farming, etc) and thermal properties of soil material, such as organic layer thickness, play an important part.

Since the phenomenon has far-reaching implications, understanding it is the first step to mitigation, they said. “Permafrost characteristics and its distribution is a crucial knowledge gap in the cryospheric system studies of the Indian Himalayan Region. There is no information or literature about the engineering challenges of permafrost in the region. Furthermore, a detailed permafrost distribution map and its characteristics are missing from the region,” said Wani.

He suggested long-term monitoring of permafrost and setting up a unified database like the Swiss Permafrost Monitoring Network (PERMOS) as the preliminary step.

Baral suggested that apart from geophysical investigations and studies, early identification of human settlements and infrastructures in regions at risk is necessary. “If feasible, these settlements and infrastructures need to be relocated to safer zones,” he said.

Another important area of concern is the dams in the permafrost regions that face the threat of being damaged in the event of permafrost thaw which would have a devastating impact on the region.

Dams and hydropower stations in these regions are at the risk of being damaged if the thawing of permafrost intensifies. Allen informed Mongabay-India that dam structures hold back water, but dams can slump due to melting and causing damage.

Tehri, Uttarakhand. Dams and hydropower stations in these regions are at the risk of being damaged if the thawing of permafrost intensifies. Photo by India Water Portal/ Flickr.

“We need dams for hydropower but going forward, more attention can be given to comprehensive risk assessments, mitigation strategies, and early warning systems to avoid disasters,” he said.

National policies of the countries that share the Himalayan mountain ranges must focus on bringing down GHG emissions by various means like limiting the use of fossil fuels, increasing forest cover, encouraging green technology, and developing renewable energy sources.

“These countries need to come together to present the evidence on global fora (e.g. COP27) and make a strong point together that globally all nations should work on implementing mitigation measures. Thawing has real-life consequences for people in the region, which are now already visible. Nobody will react if documentation and communication don’t happen,” Wani said.

By Arathi Menon

This article is republished from Mongabay.

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