Glacier Retreat in the Himalayas

Glaciers in the Himalaya are receding faster than in any other part of the world and the reason is primarily attributed to faster rising temperature in the high-altitude areas due to increased emissions of greenhouse gasses owing to anthropogenic activities.

Glacial melting/retreating in the Himalayas will not only impact river flow but will also give rise to disasters like Glacial Lake Outburst Floods, landslides, and avalanches.

Climate Change Impact on Himalayan Glaciers

The Himalayan glaciers are naturally vulnerable to climate change due to their geographical location. At the base of the Himalaya, tropical climate prevails which is characterized by constant high temperatures.

Climate change has a strong influence on precipitation over the Himalayas as well as melting response of glaciers or snow cover in Himalayas, affecting the runoff patterns of rivers originating from glaciated regions of Himalaya mountains flowing through the Asian continent and draining into the Indian Ocean (Arabian Sea and Bay of Bengal).

Also Read : Impact of Climate Change on the Himalayas.

The retreat of Himalayan glaciers and erratic monsoon patterns — two most visible impacts of climate change in and around India — are going to make life more difficult in the coming days, according to a report released at COP27 in Egypt.

Glaciers in the Himalayas support mighty Ganga, Brahmaputra and Indus rivers.

About 15,000 glaciers are found in the Greater Himalayan region which supports mighty perennial rivers such as the Indus, Ganga and Brahmaputra which, in turn, are the lifeline for millions of people in South Asian countries as well as for other species thriving in the region. 

The Gangetic basin alone is home to 500 million people, about 10% of the total human population in the region. The Himalayan rivers also play an important role in electricity production of both hydro as well as thermal through dams/power plants established in the Indo-Gangetic Plains, ensuring energy security for India. (The Third Pole and TERI).

Ice and snow in the HKH region are important sources of water for rivers flowing through 16 Asian countries providing fresh water for 240 million people in the mountain regions and another nearly 1.6 billion in the downstream regions of these rivers.

Factors Contributing To Glaciers Melting

There are a number of factors that are contributing to glacier melting in the Himalayas.

Black Carbon

Accumulation of black carbon is accelerating the melting of glaciers in the Himalayan region as it absorbs the significant sunlight and raises the surrounding air temperature. 

Black carbon is basically a soot emitted from fires in the surrounding areas, particularly in the Indo-Gangetic Plain. (Air pollution from the Indo-Gangetic Plain is main contributor to the deposition of black carbon on the mountains)

Deforestation

High population density near mountain areas led to deforestation and land-use changes which adversely affected the glaciers in the region.

Rising Temperature 

This rising temperature in the upper reaches of the Himalayas coupled with increasing rainfall and decreasing snowfall pattern is contributing to glacial retreat. The temperature is increasing at a faster rate in the upper reaches of the Himalayas as compared to the global average. The glacial shrinkage will speed up if global warming and drying continue.

Pollution

These glaciated regions are also inhabited by local people, so local pollution also impacts the melting response of these glaciers.

Today, the rapid pace of globalization, urbanization and mass tourism is threatening mountain ecosystems, resources, and communities. These factors contributing to an increase in pollution level are posing a threat to the stability of glaciers.

Effects of Glaciers Melting in the Himalayas

Affect River Regime

Glacial retreat affects river regime and may lead to reduction in amount and flow of water in the rivers originating in the Himalaya region. This will affect the Indus region more as it depends more on meltwaters as compared to the Ganga and Brahmaputra basins. 

The Indus river basin is particularly vulnerable to the long-term changes in river runoff as snow and glacial melt contribute more than 60% of runoff in the Indus river, mainly flowing through Pakistan and Northwest India. 

The Ganga and Brahmaputra basins receive significant contribution from monsoon rainfall also, decreasing their dependency to glacial melt to some extent. However, meltwater from glaciers in the Himalayas flowing into the Ganga and Brahmaputra rivers is very significant during dry seasons. 

Since the hydrology of glaciated regions is thermally controlled, the temperature rise mostly affects the timing of runoff.

Impacts Groundwater Recharge

As glaciers retreat, the amount of meltwater flowing into rivers would decline which may lead to a substantial drop in the rates of groundwater recharge in some regions as surface and groundwater systems are interconnected. (Ref– https://www.orfonline.org/research/retreating-glaciers-and-water-flows-in-the-himalayas-implications-for-governance)

Flood Outbreak

Retreat in glaciers can destabilize slopes and may give rise to catastrophic landslides which dam streams and can sometimes lead to outbreak of floods.

Excessive melting of ice and snow during rainfall can trigger flash floods and debris flows. Flooding may potentially become a major issue for development. (Compound impact of glacial retreat and changing monsoon patterns may lead to extreme weather events which put the people, particularly living in low-land coastal areas, in danger)

GLOF Formation

Glacial melt in the eastern and central Himalayas leads to formation and development of glacial lakes dammed by moraine and expansion of existing lakes. Sudden breaches in such lakes can potentially lead to events like Global Lake Outburst Floods (GLOF), sudden discharge of huge volumes of water and debris, leading to catastrophic flooding in downstream areas with huge damage to life, property, forests and infrastructures.

For example, In the 2013 Kedarnath flood disaster, a moraine-dammed glacial lake outburst created havoc downstream of Mandakini and its tributary river valleys in the region.

In 2021, a glacial burst in Chamoli district of the Uttarakhand led to flash floods in Dhauliganga river resulting in death of about 170 people.

GLOF can destabilize hydro Projects

Rapid growth of pro-glacial lakes and possibility of GLOFs events can have a widespread impact on hydrology, ecosystems and socio-economic activities. 

GLOFs can destabilize the hydropower projects in downstream Himalayan regions. Hydropower projects will reduce dependency on fossil fuels, which are main drivers of climate change.

Altogether 3624 glacial lakes have been mapped in the basins of Koshi, Gandak and Karnali rivers in India, China and Nepal. Of them 47 lakes are identified as critically dangerous that could burst, flooding in downstream regions, according to a joint report of ICIMOD and UNDP (United Nations Development Program). 

Water supply will be decreased in long-term

Increased glacial melting due to the impact of climate change would result in more water availability in rivers originating from the Himalayas, but it will be in forms of floods rather than steady flow. Eventually, water supply will dwindle due to reduction in melt water storage, posing a significant threat to the communities dependent on water from snow and glacial melt for agriculture, fishing and domestic needs.

Affect the Ecology of Himalayas

Melting of glaciers would have adverse impact on the ecology of the Himalayas, leading to shift of tree lines in the Himalaya and changing the phonology of plants. It may also have a negative impact on biodiversity conservation and ecosystem services that the region provides.

Snow lines can move upward as glacial retreats.

Glaciers in the Eastern Himalayas are melting faster than in Western Himalayas.

The eastern Himalayas are more vulnerable to climate change when compared with western Himalayas which have larger glaciers. There are evidences of glacial melting in the eastern and central Himalayas While glaciers in the western Himalayas, Hindu Kush and Karakoram range appear to be more stable, and even advancing in some regions for example, glaciers in the Karakoram Mountain range are stable and some of them are growing due to stable snowfall from westerlies.

Reason : Regional Climate Differences

The glacial melt pattern may have to do with regional climate differences, ICIMOD said. 

Climate of the Himalayas is not uniform and differs in the eastern and western Himalayas, especially in timing and type of precipitation and glacier behaviour. 

Precipitation in the eastern part of the Himalaya is strongly influenced by summer monsoon, resulting in more rainfall than snowfall While precipitation in the western Himalaya is dominated by mid-latitudes western disturbances (westerlies), resulting in more snowfall than rainfall.

These glaciers' response to climate change varies due to the diverse climate across the Himalayas.

The climate of the HKH region is changing because temperatures across the region are increasing and will accelerate in coming decades. 

What will happen if temperature continues to rise?

Many more glaciers will retreat in the Himalayas in coming decades.

Fourth assessment report of IPCC said that there is a high confidence that in the coming decades many glaciers in the region will retreat, while smaller glaciers may disappear altogether.

For example, Gangotri is the largest glacier in the Uttarakhand Himalaya which is about 30.2 km long and has been receding alarmingly in recent years.

The Gangotri glacier, from which the holy Ganga river originates, retreated by 1700 meters between 1935 and 2022, according to a study of the Wadia Institute of Himalayan Geology (WIHG). 

Reason : Reduced snowfall, and more rainfall apart from faster rising temperatures in the upper Himalayas has been attributed to this retreat. Increasing rainfall in the region is leading to faster melting of the Gangotri glacier and currently, snowfall is insufficient to replenish melting ice every year.

The Pensilungpa Glacier in Ladakh's Zanskar Valley is retreating as a result of rising temperatures and falling winter snowfall, According to recent research conducted by WIHG.

Small glaciers will be disappeared.

Small glaciers are predicted to disappear as the Himalayan glaciers are highly sensitive to temperature rise.

More than 90% of (Indian) glaciers distributed among three river basins - Indus, Ganga, Brahmaputra are small (<5 sq km) to very small (<1 sq km) in size, according to the Geological Survey of India. Only few are bigger than 10 sq km such as Siachen, Gangotri and Zemu glaciers.

Small glaciers have been estimated to show larger signs of climate change impacts and more mass loss will occur in the region, influencing water supply for the downstream regions. Even some of the small glaciers are predicted to disappear and larger glaciers will continue to shrink in coming decades.

The Himalayan glaciers are located on the southern-facing slopes of the mountains, very close to the tropics at low latitudes. Thus, there is a natural build-up of high heat content in this area.