Rising Temperatures Have Doubled Himalayan Glacier Melt—Study

The Himalayas have a powerful impact on the lives of the people who live near them: They have cultural and religious sway, they play a role in determining regional weather patterns, and they feed major rivers like the Indus, the Ganges, and the Tsangpo-Brahmaputra that millions rely on for freshwater.

A new study published in the journal Science Advances by Ph.D candidate Joshua Maurer of Columbia University’s Lamont-Doherty Earth Observatory concludes that glaciers in the Himalaya melted twice as quickly from 2000 to 2016 than they did from 1975 to 2000. “This is the clearest picture yet of how fast Himalayan glaciers are melting over this time interval, and why,” said Maurer.

Walter Immerzeel, a professor in the University of Utrecht’s department of geosciences, told GlacierHub that “the novelty lies in the fact that they go back until 1975.” He said that scientists already knew “quite well” what the mass balance rates were for the last twenty years or so, but that looking further back and over a wider area provided interesting new information.

Spiti Valley, which means “The Middle Land,” is located in the northern Indian province of Himachal Pradesh in the Himalayas. 
Source: beagle17/Creative Commons

Maurer and his co-authors examined ice loss along a 2,000-kilometer-long transect of the Himalayas, from western India eastwards to Bhutan. The study area includes 650 of the largest glaciers in the Himalaya and confirms the results of previous studies conducted by researchers who looked at the rate of mass loss in the Himalaya. 

The new study makes a major contribution by indicating that regional warming is responsible for the increase in melting. The researchers were able to determine this because mass loss rates were similar across subregions despite variations in other factors like air pollution and precipitation that can also accelerate melting.

Immerzeel agreed with the findings. “It is mostly temperature change driving the mass balances,” he said. “It can be locally enforced by black carbon or modulated by precipitation changes, but the main driving force is a rise in temperature.” 

The analysis was conducted using images from declassified KH-9 Hexagon spy satellites which were used by US intelligence agencies during the Cold War. The satellites orbited Earth between 1973 and 1980, taking 29,000 images that were kept as government secrets until relatively recently when they were declassified, creating a cornucopia of data for researchers to comb through.

Maurer and his co-authors used the images to build models showing the size of the glaciers when the images were created. The historical models were then compared to more recent satellite images to determine the changes that occurred over time. Only glaciers for which data were available during both time periods were included in the study.


A diagram of a KH-9 Hexagon satellite that was used to create the images used in Maurer’s study. 
(Source: National Reconnaissance Office)

The new study received widespread media attention. National Geographic, CNN, the New Yorker, and The Guardian, among other major publications, highlighted the study’s conclusion that mass loss in Himalayan glaciers has doubled in the last forty years.

Tobias Bolch, a glaciologist at the University of St Andrews, told GlacierHub the findings should be approached with caution. “The statement about the doubling of the mass loss after 2000 compared to the period 1975-2000 should be formulated with much more care.”

“[Scientists],” he continued, “need to be very careful presenting results about Himalayan glaciers and should communicate them correctly specifically after the IPCC AR4 error, and the wrong statement about the rapid disappearance of Himalayan glaciers.”

Bloch is referring to an error that occurred in 2007, when the IPCC included in its Fourth Assessment Report an inaccurate statement predicting that all Himalayan glaciers would be gone by 2035.

“It is a promising data set, but due to its nature there are large data gaps which need to be filled which makes the data uncertain,” Bolch said.

He added that there is “clear evidence” that mass loss has accelerated in the Himalaya.

A recent report by the International Centre for Integrated Mountain Development, a regional intergovernmental organization in Nepal working on sustainable development in mountains, predicts that the Himalayas could lose 64 percent of their ice by the year 2100.

Maurer’s study examines only past melting from 1975 to 2016.  ICIMOD’s study provides additional dimension to Maurer’s results. 

A stretch of the Indus River. 
(Source: arsalank2/ Creative Commons )

The large amount of melting that may occur in the coming decades would result in greater quantities of meltwater entering rivers. The Indus River, which millions rely on for drinking water and agriculture, receives about 40 percent of its flow from glacial melt. An increase in meltwater could augment the risk of flooding of the Indus and other rivers in the region. 

Similarly, there may be a greater number of glacial outburst floods. Outburst floods occur when the moraine, or rock wall, which acts as a dam collapses. A collapse can take place for various reasons including if a great deal of water accumulates in a lake from a phenomenon like an increase in glacial melting. Depending on the size of the lake and downstream populations, among other factors, these floods have the potential to cause substantial damage. The largest of these floods have killed thousands of people, swept away homes, and even registered on seismometers in Nepal. 

Reflections in a glacial lake in Norway. 
(Source: Peter Nijenhuis/ Flickr)

Once glaciers have lost substantial amounts of mass and no longer have large quantities of water to release, the reverse will begin to cause problems: Rivers dependent on Himalayan glacial melt will diminish and drought may become more common downstream. This will negatively affect farming and development in the Himalayan region.

In both the short and long term, according Maurer and his colleagues, glacier melt in the Himalayas will have significant impacts on the livelihoods of those dependent on its towering peaks.

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Asia’s Water Supply Endangered by Third Pole Warming

It is well known that warming will deeply affect glaciers and ice at the poles. Many of the effects are observable today and will continue to impact wildlife, people, and their environments. Scientists are now beginning to better understand climate change in cold regions, such at the Andes and the Alps, outside the polar regions of the Arctic and Antarctica.

In a recent news article by Nature, researchers look at the climatological and glacial changes in the ‘third pole’, which encompasses the Himalayas, Hindu Kush, Karakoram and the Tibetan Plateau. They also consider the need for enhanced monitoring of the glaciers and water supply, to help scientist better understand the extent of glacier retreat now and in the future.

Third Pole Water in Sustaining Asian Societies

The Ganges river flows through India and Bangladesh. It is one of the most sacred rivers in Hinduism, and millions rely on its water for daily life. (Source: Travelbusy.com/Flickr)

The third pole is one of the major freshwater resources in Asia. Meltwater from glaciers feed into some of the major rivers in Asia, including the Ganges, Yangtze, and Brahmaputra rivers. According to the article, these river basins provide critical freshwater resources to about one-fifth of the world’s population.

Water is inextricably linked to the rise of Asian societies, bestowing them with rich agricultural output and ensuring stability and longevity in a sometimes brutal climate region.The struggle for water in modern history is a global story… But nowhere has the search for water shaped or sustained as much human life as in India and China” says Sunil Amrith in a feature by Quartz India.

A dependable, predictable supply of meltwater is the pillar upon which these societies rest. Climate change could topple that foundation. As groundwater and aquifers dry up in India, water resources from glaciers will become even more necessary. Analysts from NITI, a policy think tank in India, said to New Security BeatCritical ground water resources that account for 40 percent of India’s water supply are being depleted at unsustainable rates”. Hydropower is a growing clean and renewable energy resource for many sectors across China, and irrigation plays a substantial role in crop production for rural communities. The loss of glaciers and rivers could mean dire economic impacts on these regions.

Projected Changes in Climate and Peak Water

Climate patterns over the third pole are now shifting. As temperatures rise and glaciers continue to melt, more glacial lakes will form and river will begin to dry out. The authors cited recent research which indicated that a projected weakening of the annual Indian monsoon will bring significantly less precipitation and snow over the Himalayas. As a result, the current mass-balance of glaciers in the region will be offset by more runoff than snow accumulation.

Many of the world’s highest peaks can be found in the Himalayas, including Mount Everest. This region is considered to be active and prone to tremors, earthquakes, and landslides. Falling ice from glacier melt present an additional natural hazard. (Source: weinkala/Flickr)

The change in mass-balance results in glacier retreat, occurring faster today than historic rates of decline. Eventually, many glaciers will reach their peak water output, with some as early as 2020. Peak water is the level at which glacier melt water output is at its maximum, and it’s considered to be the “tipping point” of water supply. Societies may benefit from the peak water with temporary outflow of more meltwater in rivers, yet the long-term effects will be detrimental.

Although peak water is short-lived, it will be particularly advantageous to some areas projected to experience less precipitation. However, once glaciers reach this level, they will continue to output less and less water. Other regions such as the Andes will also experience peak water, with many glaciers having already have met this max water output level. The loss of glaciers and rivers could be disastrous to dependent societies.

Room for Improvement: Monitoring Retreat and Risks

The authors also wrote about the hazards and risks associated with glacier retreat. Communities living in mountainous regions face with the risk of collapsing debris from glaciers. According to the piece, in October 2018, glacier debris and the resulting landslide dammed the Yarlung Tsangpo River. This led to flooding downstream, affecting regions as far as Bangladesh. According to an article by AGU100, a prompt evacuation prevented any lives from being lost.

Glacial avalanches pose a considerable threat to millions along Asia’s vast network of rivers and streams. According to researchers from the article, only 0.1 percent of glaciers and lakes in the region have monitoring stations, and few high-altitude areas have weather stations. There are plans to install over 20 new stations in the third pole area, which is a big improvement from the current 10 stations in the area. Proper training is necessary to properly operate weather monitoring technology and adequate collection of data.

This map outlines the third pole region, depicting the distribution of monitoring stations, as well as some major glaciers and river networks. (Source: Gao et al./Nature)

The study also prioritized the importance of sharing this data with global and regional climate models, and making the needs of the local people central in climate change discussions. It is imperative that the changes in the third pole to be globally recognized, to better serve local communities and societies in safeguarding water security and cultivating sustainability.

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