Everest glaciers mostly gone by end of century (probably)

Eric Hopton for redOrbit.com – Your Universe Online

The glaciers of the High Mountain Asia region, which includes the Himalayas, contain the largest volumes of ice outside the Polar Regions, but a new scientific model of glaciation has predicted that glacier volume could be reduced between 70% and 99% by 2100. The effect of such huge losses and the dramatically increased river flows downstream could be catastrophic for the area’s communities.

Everest region could change forever

A team of researchers from Nepal, France, and the Netherlands claim that, if greenhouse-gas emissions continue to rise, glaciers in the Everest region of the Himalayas could experience dramatic change in the decades to come. Sustained ice loss through the 21st century is likely according to the research, published today in The Cryosphere, an open access journal.

“The signal of future glacier change in the region is clear: continued and possibly accelerated mass loss from glaciers is likely given the projected increase in temperatures,” says Joseph Shea, leader of the study and a glacier hydrologist at the International Centre for Integrated Mountain Development, Kathmandu, Nepal.

“Our results indicate that these glaciers may be highly sensitive to changes in temperature, and that increases in precipitation are not enough to offset the increased melt,” added Shea.

Increased temperatures will not only increase the rates of snow and ice melt, but can also result in a change of precipitation from snow to rain at critical elevations, where the glaciers are concentrated. Together, these act to reduce glacier growth and increase melting of exposed areas.

The team studied glaciers in the Dudh Kosi basin in the Nepal Himalaya, home to some of the world’s highest mountain peaks, including Mt Everest, and to over 250 square miles of glaciers.

Local populations threatened

Changes in glacier volume can impact the availability of water, with consequences for agriculture and hydropower generation. Increased glacier melt initially increases water flows. But further retreat leads to reduced meltwater from the glaciers during the warmer months.

Glacier retreat can also create lakes due to damming by glacial debris. If avalanches or earthquakes breach the “dams,” devastating floods can result in river flows 100 times greater than normal in the Kosi basin.

The team started using field observations and data from local weather stations to calibrate and test a model of glacier change over the past 50 years. They then applied eight temperature and precipitation scenarios to the historical data and tracked how glacier areas and volumes responded.

Part of the glacier response is due to changes in the “freezing level,” the elevation where mean monthly temperatures are 0°C. The freezing level currently varies between 3200 m in January and 5500 m in August. But the model predicts this could increase by 800-1200m. This would expose over 90% of the current glaciated area to melt in the warmer months, according to study co-author Walter Immerzeel.

Though the researchers are cautious about the results, they state that, “The signal of future glacier change in the region is clear and compelling,” and that decreases in ice thickness and extent are expected for “even the most conservative climate change scenario.”

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Source: http://www.redorbit.com/news/science/1113398140/everest-glaciers-mostly-gone-by-end-of-century-probably-052715/