Permafrost thaw, a ticking time bomb beneath our feet

Permanently frozen terrain covers 22% of the Earth's surface. This area is more than 112 million square kilometres. People call it permafrost, akin to a ticking time bomb beneath our feet. Global warming is causing this permafrost to thaw, leading to potentially catastrophic consequences for the climate. This, in turn, could put the future of life on the planet in jeopardy.

Permafrost, the permanently frozen layer of soil, rock, or sediment that covers nearly a quarter of the Earth’s land surface, is now starting to thaw. This phenomenon, largely unnoticed by the public, has potentially disastrous consequences for our climate.

The Intergovernmental Panel on Climate Change gave considerable attention to Permafrost in their fifth assessment report, but much of the focus lies on studies from the European Alps, according to Stoffel. It also mentions that data on the Hindu-Kush Himalayas, where many people live in areas that either have permafrost or will be impacted by its melt, is absent."

Global warming, primarily due to heat trapped by carbon dioxide from burning fossil fuels, has thawed permafrost in recent decades. The National Oceanic and Atmospheric Administration reports that Arctic warming has been rising at twice the global average rate since 2000. This increase is accelerating the thaw of permafrost, causing the organic carbon within it to break down and release carbon dioxide, thereby exacerbating climate change.

What is Permafrost?

People find permafrost in northern polar regions and at high altitudes, covering 22% of the Earth’s land surface. Permafrost is most common in regions with high mountains and in Earth's higher latitudes, near the North and South Poles.  Permafrost occurs when the mean annual temperature is −2 °C (28.4 °F) or below. In the coldest regions, the depth of continuous permafrost can exceed 1,400 m (4,600 ft). 

When permafrost melts, the land above it sinks or changes shape, and the shifting ground could potentially damage buildings and infrastructure such as roads, airports, and water and sewer pipes. It also causes landslides, slope collapse, and glacial lake outburst floods (GLOFs) and topples trees.

First impression of permafrost in India

A team in India studied permafrost in the region, focusing on the areas where it exists and where it’s nearing its melting point. The latter is critical as it heightens the risk of rock fragmentation and debris flow.

The study employs various methods such as satellite imagery to identify potential permafrost features like tongue-shaped rock glaciers, and mapping areas with active and fossil permafrost features. People see rock glaciers, or frozen rock debris bound by ice, as key indicators of permafrost.

The scientists will also merge permafrost analysis with hazard assessment to create a framework for evaluating risks and vulnerability to natural hazards in the Himalayas.

Areas downstream are also susceptible to the effects of permafrost thawing. As N.B. Kishore Tripura, secretary, Ministry of Chittagong Hill Tracts Affairs, Bangladesh, stated at an international conference, the melting of Himalayan permafrost could lead to river floods downstream in neighboring Bangladesh.

While the Indo-Swiss study will provide insights on a local level, another project by the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD) aims to offer a comprehensive view of permafrost in the entire Hindu-Kush-Himalayan region. They began this project in 2013 and have set it to conclude in mid-2015.

Hindu Kush's Climate & Permafrost

The cryosphere, the frozen part of the Earth’s surface, is highly sensitive to climate change. This sensitivity is evident in the widespread retreat of mountain glaciers. Similarly, climate change also affects subsurface ice contained in permafrost, leading to lasting impacts on both natural and human systems.

Unlike glaciers, we cannot spatially observe permafrost, often resulting in overlooking its presence and potential changes. Consequently, we know little about the permafrost in the mountains of the Hindu Kush Himalaya (HKH) region, even though the permafrost area exceeds that of glaciers in nearly all countries in this region.

Based primarily on evidence and insights from other global permafrost areas, this review provides a synopsis of the knowledge or inferred facts about permafrost in the HKH region. Due to the extreme nature of the environment, we expect the diversity of conditions and phenomena found in permafrost to exceed what researchers previously described and investigated.

Predictions suggest that climate change, combined with increasing development, will cause diverse permafrost-related impacts on vegetation, water quality, geohazards, and livelihoods. We need a deeper understanding of high-elevation permafrost in subtropical latitudes and the pathways connecting environmental changes and human livelihoods to better anticipate and mitigate these effects. This understanding will play a crucial role in developing strategies to deal with the changes that the thawing of permafrost causes in the HKH region.

Permafrost thawing also makes downstream areas vulnerable to its impacts. "The melting of Himalayan permafrost would also contribute to river floods downstream in neighbouring Bangladesh," N.B. Kishore Tripura, secretary, Ministry of Chittagong Hill Tracts Affairs, Bangladesh, informed an international conference on mountain people adapting to climate change. They held the conference in Kathmandu in November.

Landslides, floods and loss of wildlife habitat

The UNEP report warns that widespread degradation of permafrost could permanently alter local hydrology, leading to an increase in fire and erosion disturbances. This could also affect critical habitats, especially for migratory birds.

The report further warns of increased risks associated with rock fall and erosion, particularly in cold mountain areas. Damage to critical infrastructure like buildings and roads could lead to significant social and economic costs.

Experts from ICIMOD suggest that glacial lakes or hydropower dams near mountains with permafrost could see an increase in rockfall hazards. This could lead to outburst floods with serious downstream consequences.

Arun Bhakta Shreshtha, regional programme manager, river basin development, in ICIMOD, said, “Permafrost is the least studied part of the three components of the Himalayan cryosphere – the frozen part of earth. Most of the attention is on the other two components: glaciers and snow, as they are visible and one can observe their changes.”

He added, “Glaciers also have a dramatic aura about them, while snow cover is huge, and so any changes in them can be not only observed long-term but also updated regularly. “Rock glaciers have a substantial amount of ice, and move at the rate of 1-2 decimetres to 1-2 metres every year. But in the last three or four years, they have been observed to be moving at a rate of 100-150 metres every year, which is being attributed to rising temperatures.”

When permafrost in moraines and debris slopes thaw, they deposit the sediments in the lower reaches of rivers. This could occur as a slow and steady process, or as a catastrophic event combined with extreme precipitation, destroying downstream infrastructure such as houses, bridges, and roads.

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