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Thorthormi glacier recedes by 1.2kms in last 16 years

At the current receding rate, the glacier is estimated to completely melt in 50 years

The Thorthomi glacier has receded by 1.2kms in the last 16 years, according to a research by a volunteer expert with Japan International Cooperation Agency (JICA), Jun Saito.

Jun Saito teaches researchers to use Quantum Geographic Information System in Bhutan.

The glacier has receded by 75.6 meters every year, making the rate twice higher than the 1990s. Jun Saito said that the Thorthormi glacier, which is about 4kms today, would melt completely in 50 years if the receding rate continues.

The study was presented at the 4th Annual Bhutan Ecological Society Symposium in Thimphu.

He said the receding rate was 37.2 meters between 1990 and 2000. “Glaciers recede due to the melting of the glacier edge and iceberg calving, meaning the glacier edge breaks into ice chunks.” Thorthormi lake has a high risk of Glacial Lake Outburst Flood (GLOF) in Bhutan.

In addition to Thorthormi glacier melting, water from Lugge lake, which is close to Thorthormi lake, might merge in future. “The frontal position of Chubda glacier in Bumthang has also been receding rapidly. The rate is accelerating lately.”

Chubda glacier receded 14.7 meters annually until 2000. However, today the rate is 26 meters annually.

Jun Saito said that iceberg calving forms the lake in front of the glacier and causes the glacier front position to recede more, increasing the amount of water flowing into the lake at the edge of the glacier.

The volunteer studied 21 glaciers in the country in July 2016 and found that 18 glaciers showed an accelerating change in the glacier frontal position.

He said that after Thorthormi glacier, Lugge, which burst in 1994, is also receding at a high rate. “Lugge glacier receded 0.6 km.”

The study showed that the ice speed of Thorthormi glacier was 49 meters annually. Lugge glacier moved 24.2 meters annually.

The increasing temperature affects the ice speed of a glacier. “I have observed that as the ice speed increases, the glacier frontal position is also increasing rapidly. The acceleration leads to receding of glaciers by increasing the discharge into the lake.”

The study has shown that most glaciers, however, didn’t move at all in Bhutan. “Only five glaciers of the 21 studied showed higher ice speed. Thorthormi glacier was one of them.”

With 0.34 giga tonne of water consumed annually in Bhutan, Jun Saito said that the glaciers in Bhutan have the capacity to supply water for 150 years more.

However, because drinking water also consist of rain and snow, the number can change.

He added that GLOF is a result of water surface in glacial lake increasing due to ice body, an avalanche of rock or heavy snowfall in the lake triggered by an earthquake. “A large amount of water released from glacial lake cause immense damage downstream.”

Although the country has been studying the glacial lakes that possess GLOF risk, Jun Saito said that most field measurements have not targeted glaciers but glacial lakes.

“We need to monitor Chubda glacier as well as the lake as they are fluctuating during a long period.”

More than 25 glacial lakes have been identified as dangerous in the country. There are 1,583 glaciers in the country today. These glaciers have resulted in 2,674 glacial lakes.

Phurpa Lhamo

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