A meltwater imbalance from Earth’s 3rd Pole

Earth's 3rd pole: Map of Hindu Kush Himalayas mountain range and the Tibetan Plateau.
Earth’s 3rd Pole, aka the Asian Water Tower, is the region that encompasses the Hindu Kush Himalayas mountain range and the Tibetan Plateau. This area is the 3rd largest reservoir of snow and ice on the globe after the Arctic and Antarctica. It supplies water to 25% of Earth’s population. The region has warmed at rates significantly higher than the global mean. Annual and seasonal temperatures have increased more at higher elevation zones across the 3rd Pole. Glaciers are retreating, permafrost degrading, and snow cover days decreasing at the 3rd Pole. Map via Caption via TPE.

Earth’s 3rd Pole is melting

The Hindu Kush Himalayas mountain range and the Tibetan Plateau are sometimes called Earth’s 3rd Pole. The region comprises the largest store of frozen water after Earth’s North and South Poles. This so-called Asian Water Tower supplies much of Asia – 25% of Earth’s population, about 2 billion people – with fresh water.

Scientists have known for some time that Earth’s 3rd Pole is melting and that flooding will become an issue, likely between 2030 (or earlier) and 2050, when annual glacier runoff will reach a maximum. Afterwards, water shortages will begin. This month (June 7, 2022) – while acknowledging that the region’s future “remains highly uncertain” – scientists released a new study suggesting that an imbalance in the way meltwater runs off will cause those north of the region to have a greater supply of water, in the short run, while those in the south will face more immediate and greater shortages.

The scientists are associated with TPE (Third Pole Environment). TPE has established an observation network which includes 51 sites tracking glacier thickness changes, 35 on glacier mass balance, 16 following permafrost changes, six on snow cover changes as well as 16 collecting hydrological and meteorological data. Initiated in 2009 by three scientists, TPE is part of UNESCO and calls itself:

… an international program for the interdisciplinary study of the relationships among water, ice, air, ecology and humankind in the Third Pole region and beyond.

The scientists published the new study in the peer-reviewed journal Nature Reviews Earth & Environment on June 7, 2022.

A section of Earth with a large glowing round white patch on a mountainous area: Earth's 3rd Pole.
Earth’s 3rd Pole. Graphic via TPE.

3rd Pole runoff from glaciers isn’t balanced

As the paper explained:

During 1980–2018, warming of the Asian Water Tower was 0.42 degrees C [about .8 degrees F] per decade, twice the global average rate.

They said their study:

… synthesize[d] observational evidence and model projections that describe an imbalance in the Asian water tower caused by accelerated transformation of ice and snow into liquid water. This phase change is associated with a south–north disparity due to the spatio-temporal interaction between the westerlies and the Indian monsoon.

In other words, although global warming itself is causing the overall melt, the westerlies (prevailing winds) and the Indian monsoon have created an imbalance. The researchers said that, as the transformation of ice and snow into liquid water accelerates, the amount of liquid water in the north will (temporarily) increase while the supply in the south will decrease. This imbalance will alleviate water scarcity in areas such as the Yellow and Yangtze River basins in the short term. On the other hand, they said, it will increase scarcity in the Indus and Amu Darya River basins.

Yao Tandong, lead author and co-chair of Third Pole Environment, said:

Such imbalance is expected to pose a great challenge to the supply-demand balancing of water resources in downstream regions.

The Asian Water Tower’s future

So these scientists think it’s possible that populations north of the Tibetan Plateau will have a greater supply of water, longer, while populations in the south will experience a greater demand for water more quickly. Scientists predict the highest demand for water will be in the southern Indus basin. The demand is largely due to irrigation for farmland. In fact, 90% of water usage in this region goes to irrigation to help feed the area’s great population. The Indus and Ganges Brahmaputra River basins are home to the world’s largest irrigated agricultural area.

The researchers said the north-south disparity will increase – in the coming decades of this century – as the climate warms. Piao Shilong of Peking University and the Chinese Academy of Sciences said:

Actionable policies for sustainable water resource management are greatly needed in this region.

The researchers also said more studies will help provide more information to the people of the region so they can anticipate the changes. Lonnie Thompson of the Ohio State University and co-chair of Third Pole Environment said:

We need more accurate predictions of future water supply to assess mitigation and adaptation strategies for the region.

Three of the scientists’ future goals are comprehensive monitoring stations, advanced modeling and sustainable water management.

A graphic showing glaciers, with run-off between them, and a caption: "Scientists estimate that, by 2100, these glaciers could be 75% smaller in volume."
This image is a screen shot from a video titled NASA Tracks Future of Asia’s Glaciers.

Bottom line: An imbalance in runoff from melting glaciers at Earth’s 3rd Pole – aka the Asian Water Tower – may mean more water supply in the north and less in the south.

Source: The imbalance of the Asian water tower


Read more: Hundreds of millions of South Asians at risk from glacier melt

June 13, 2022

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