Floods could triple across Himalayas, Tibetan Plateau as planet warms

As the global temperature continue to climb and glaciers melt more rapidly, new research suggests the risk of flooding across the Himalayas and Tibetan Plateau could triple.

In addition to putting communities and infrastructure in harms way, the predicted increase in lake outburst floods -- detailed Thursday in the journal Nature Climate Change -- could jeopardize water supplies in politically fragile regions like Kashmir.

Over the last few decades, global ice loss rates have rapidly accelerated. Alpine glaciers have proven especially vulnerable to rising temperatures.

Many of those glaciers are found on Earth's so-called Third Pole, the region that encompasses the Himalayas, Tibetan Plateau and surrounding mountain ranges.

The Third Pole hosts thousands of glaciers and glacial lakes that act like a massive water tower, supplying water to billions of people throughout Asia.

Both natural and human-built dams help control these water reserves, but increased melt rates have caused glacial lakes to swell, putting pressure on local levees.

To better understand how ongoing warming trends will affect flood risks in the region, scientists combined satellite imagery and topographic modeling.

The analysis helped researchers classify thousands of glacial lakes as either high or very high risk.

"We then compared our results with a catalogue of past glacial lake floods, which allowed us to validate our approaches," study co-author Simon Allen said in a news release.

"Once we confirmed that the approaches accurately identified current dangerous lakes, we could then apply these methods to future scenarios," said Allen, a researcher at the Institute of Environmental Sciences at the University of Geneva in Switzerland.

Researchers ran models under three different warming scenarios. If warming trends continue unabated, under a "business as usual scenario," most of the Third Pole's lakes will reach peak risk by the end of the century.

Models showed flood risk isn't only increased by a lake's expanding volume, but also its encroachment upon steep mountainside banks, where rock slides can trigger a dam breach.

"The speed at which some of these new hazardous situations are developing surprised us," said co-author Markus Stoffel.

"We are talking a few decades not centuries -- these are timeframes that demand the attention of authorities and decision-makers," said Stoffel, professor at the Institute for Environmental Sciences.

If policy changes fail to slow global warming and temperatures continue to increase, models showed the number of glacial lakes at a high or very high risk of flooding will increase from 1,203 to 2,963 by 2100.

The analysis also showed hotspots for flood risks will likely emerge in the Western Himalaya, Karakorum and Central Asia.

While populations in some of the at-risk regions have experienced flooding in the past, scientists expect flood patterns across the Third Pole will shift, becoming less predictable.

"Authorities and communities will be less familiar with the types of spontaneous events we consider here in a deglaciating landscape, so this calls for awareness raising and education on the new challenges that will emerge," Stoffel said.

The latest findings also suggest flood risk will increase among hundreds of glacial lakes along contested national borders, the researchers said.

Political tensions along the China-Nepal border, for example, could complicate efforts to prepare for, predict and respond to flooding disasters.

Scientists hope their research will not only encourage action of climate change mitigation, but also spur the nations of the Third Pole to work together to prevent -- and also prepare for -- future glacial flood disasters.

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Global glacier retreat has accelerated
Zurich, Switzerland (SPX) May 04, 2021
Glaciers are a sensitive indicator of climate change - and one that can be easily observed. Regardless of altitude or latitude, glaciers have been melting at a high rate since the mid-20th century. Until now, however, the full extent of ice loss has only been partially measured and understood. Now an international research team led by ETH Zurich and the University of Toulouse has authored a comprehensive study on global glacier retreat, which was published online in Nature on 28 April. This is the ... read more