- Of the estimated 200,000 glaciers in the world, the Himalaya-Karakoram range is home to 39,660. Of these, only 24 have been consistently monitored for their glacier mass balance which indicates whether a glacier is growing or shrinking.
- It is crucial to monitor glacial health to understand the relationship of glaciers with climate and hydrology in the region. But high elevation and challenging atmospheric and climatic conditions make it difficult to monitor.
- While it may not be possible to monitor every glacier, experts suggest demarcating micro-climatic regions and monitoring a glacier in each of them as a representative of the whole region.
The Himalaya-Karakoram (HK), a 2,500 kilometre-long mountain range, straddles the border between India in the east and across Bhutan, Nepal, northern India, and Pakistan in the west. This region is home to over 39,660 glaciers, covering 42,525 square kilometres across three river basins: Indus, Ganges and Brahmaputra.
Researchers say that the HK region has a much higher number of glaciers than any other mountain range on Earth.
When snow falls and accumulates new layers over time, it gets compressed into large, thick masses of ice, forming glaciers. The upper part of the glacier — called the accumulation zone — receives precipitation in the form of snow, which accumulates over time. But in the lower part of the glacier — called the ablation zone — there is more melting of the snow and ice than accumulation. The balance between the accumulated and melted snow is known as the glacier mass balance, which determines the health of the glacier. Glaciers are crucial for downstream communities as they provide drinking water, or water for irrigation. Alternatively, nutrients present in glacier melt support marine life and food chains. Glaciers also regulate river flow and counter global warming.
Knowledge of the climate-glacier relationship is still partial, notes a 2018 paper published online by Cambridge University Press. Hence, studying and monitoring glaciers, especially in remote areas such as the HK, is crucial. However, only 24 glaciers in the HK range are currently being monitored.
“We don’t need all the glaciers to be monitored but we need at least one long-term series of measurements in every one of these Himalayan regions to be able to understand what’s happening,” Inés Dussaillant Lehmann, a glaciologist at the World Glacier Monitoring Service (WGMS), University of Zurich in Switzerland, told Mongabay-India.
Read more: Himalayas losing glaciers and snow
Need to monitor glaciers
To understand how glaciers evolve — if glacier mass is growing, shrinking, or remaining the same — glaciologists say it is important to monitor glaciers on a yearly basis. The snow accumulation and the snow melt is measured throughout the hydrological year, to determine the glacier’s health.
Of Nepal’s glaciers, which fall under the Central Himalayas, less than ten (only seven glaciers) are being monitored. Three of these — Mera glacier, Changri Nup glacier and Pokalde glacier — are located within the Dudh Koshi basin, in Nepal’s Khumbu area, home to Mount Everest.
WGMS has classified the Mera and Pokalde glaciers as benchmark glaciers — glaciers that have more than 10 years of ongoing field-based measurements.
Mera glacier has been monitored since 2007 at least once a year (in November). “Its mass balance series is the longest continuous field-based series in the Central Himalayas and second longest in the entire Hindu Kush Himalayan region,” said Dibas Shrestha, an assistant professor and field glaciologist at Tribhuvan University, Nepal.
“It [Mera Glacier] can tell us what is happening with the surrounding glaciers,” said Dussaillant. According to her, in the last two years, there has been no accumulation of snow at the top of Mera peak (6,476 metres), which means that the glaciers are not getting new snow but are just losing ice. “This measurement is telling us that the melt of the glaciers has been accelerating in the last years,” she warns.
Researchers aim to continue measurements of Mera glacier for at least 30 years to make it a reference glacier.
As most glaciers in the Himalayas are located at high elevations and challenging atmospheric and climatic conditions, it becomes difficult to gather data.
“It is not only hard to reach these locations, but this fieldwork also requires ample resources and highly motivated people,” said Shrestha. “Measuring glaciers is not easy because we need to go to the same glaciers at least once or twice a year.”
Due to the complexity of the Himalayan topography, glacial measurements cannot be regionalised, for the entire range. “We cannot say that the entire Himalayas behave like that [in similar ways],” explained Dussaillant.
Instead, she suggests demarcating micro-climatic regions across the Himalayan range and monitoring a glacier in each of them as a representative of the whole region.
Impact of monsoon
According to a 2017 paper in the Journal Of Glaciology, the three glaciers — Mera, Changri Nup and Pokalde — studied between 2007-2015, are “sensitive to precipitation, and occasional severe cyclonic storms originating from the Bay of Bengal.”
There are two air circulations that dominate the Himalayas, explains Mohd. Farooq Azam, glaciologist and an associate professor at IIT, Indore. The Western Disturbances dominate the Western Himalayas, Karakoram and Hindu Kush in the winters. The South Asian Monsoons — which includes the Indian Summer Monsoons — mainly dominate the eastern and central Himalayas in the summers. “The Indian Summer Monsoons, that reach the HK, mainly come from the Indian Ocean, Bay of Bengal and Arabian Sea, affecting the Eastern Himalayas and Central Himalayas — Sikkim, Bhutan and Nepal,” he shared.
According to Fanny Brun, researcher at the University of Grenoble and the author of the 2017 paper, the maximum precipitation in this region happens “during the monsoons or pre-monsoons, from April until the end of September.”
When monsoon approaches, it sheds precipitation as it moves. “The moisture coming from the Bay of Bengal hits the Himalayan foothills. It rains and leads to cooling or decompression of air which triggers precipitation,” explained Brun. This results in the maximum rainfall intensity closer to the foothills and in what is known as the orographic effect, the air lifts and dries as it moves to higher elevations.
“When you go along the big valleys like Khumbu, it [the air] gets drier when at a higher elevation. There is still a lot to understand on what happens to the air parcels that travel along the valley,” Brun said.
The amount of precipitation glaciers receive differs based on multiple factors like glacier location, altitude, accumulation area, microclimate and topography. Glaciers that are hit by monsoons first will receive more precipitation than glaciers that are in the far interior.
“The three glaciers we study behave differently because Mera [glacier] is higher than Pokalde [glacier] and Changi Nup glacier. And it’s also located in a wetter region, so we record more precipitation at the location of Mera,” said Brun. “This is mostly due to the fact that Mera is more to the south of the mountain range. The air has more moisture.”
Read more: [Interview] Glaciologist Anil Kulkarni on shrinking glaciers
Delayed rains and increasing cyclones
In recent years, the India Meteorological Department (IMD) has issued multiple warnings for cyclones, the most recent being Cyclone Remal in May 2024.
“If there is frequent cyclonic activity in the Bay of Bengal or Arabian Sea, it will have a positive impact [on the glaciers],” explained Shrestha. This is because the precipitation brought by cyclones increases glacier mass balance.
Cyclones last about two to three days but bring a huge amount of precipitation in liquid form (rain) in the lower elevations and solid form (snow) in the high elevation basin. The cyclone Phailin, which made landfall in India in October 2013, was more active in eastern Nepal. “It produced a strong accumulation of snow at the Naulek automatic weather station (5,360 metres) on Mera glacier — one metre of snow in 48 hours,” said Shrestha. The cyclone caused one of the least negative annual-specific MB (mass balance) of Changri Nup and Pokalde glaciers, and one of the most positive MB on Mera glacier.
But when Indian summer monsoons get delayed, the late precipitation affects glaciers’ mass balance. Normally, delayed monsoons are related to strengthening El Nino conditions over the equatorial central Pacific in May, explained Shreshtha. This is the condition when the sea surface temperature over the West Pacific is colder than normal condition. This is a periodic phenomenon that occurs every 5-7 years, he added.
Compared to glaciers in the Alps and Alaska, glaciers in the Central Himalayas are summer accumulation glaciers. “80% of annual precipitation occurs during the summer months from June to September,” said Shrestha. According to him, if precipitation is reduced during the monsoons, there is less snowfall in the accumulation area of the Himalayas, and that will impact glacier mass balance.
“A delayed monsoon extends the period of intense solar radiation, allowing for a longer window of time for glacier melt. Moreover, the absence of fresh snow on the glacier surface further amplifies melting,” Shrestha explained.
For the glacier system to function, it needs input, that is snowfall. Year after year, this snow accumulates and turns into ice. When glaciers move downwards and reach areas with high temperatures, it provides meltwater for communities that live downstream.
But, according to Dussaillant, “High temperatures are going to make [the] ice melt much more so the [glacier mass] balance will be negative instead of positive, and we will be losing these water towers faster.”
The reporting for the story was supported by the Himalayan Climate Boot Camp 2024, held in Khumbu, Nepal, between May 1-14.
Banner image: Researchers monitor the Rikha Samba glacier, elevation range 5,420-6,440 metres in Nepal’s Langtang valley. Image by Dibash Shrestha.
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