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Debris cover slowing melt of Pakistan's Karakoram glaciers - scientist

Source: Thomson Reuters Foundation - Tue, 22 Oct 2013 10:12 GMT
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Baltoro Glacier in Pakistan's Central Karakoram National Park. ©WALKABOUT FILMS/Nisar Malik
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ISLAMABAD (Thomson Reuters Foundation) - For the past several years, the large glaciers of Pakistan’s Karakoram mountain range were thought to have been stable, with some even advancing slightly. But scientist Christoph Mayer, recently back from doing field studies on the glaciers, believes their future remains negative as the planet warms.

The phenomenon of these glaciers that appear not to have shrunk - at odds with the retreat of other mountain glaciers worldwide due to rising temperatures - has been dubbed the “Karakoram Anomaly”. But Mayer isn’t convinced.

“Glaciers in the Karakorams have been stable for the last 10 years, but it depends if you look at the details,” the German glaciologist from the Bavarian Academy of Sciences and Humanities told a conference in Islamabad in September.

Since 2011, Mayer has been supported by the Italian Ev-K2-CNR research association, which promotes scientific work in the mountains of the Hindu Kush-Karakoram-Himalayan region, and Pakistan’s SEED project, which aims to develop the Central Karakoram National Park.

This summer, the glaciologist again took a team of colleagues from the Pakistan Meteorological Department and the Islamabad-based Global Change Impact Studies Centre up to the Karakorams to study the Baltoro Glacier, one of the largest in the world.

Experts say the Indus River, a lifeline for Pakistan, is dependent on glacial melting for as much as half of its flow. So its fate, and that of millions of people who use its waters for agriculture, are closely connected to the health of Pakistan’s large glaciers. Most of them are located in the Karakorams, with 711 in the Central Karakoram National Park alone.

Scientists working with Ev-K2-CNR say that, in today’s era of climate change, knowledge of glaciers’ “state of health” is crucial for determining water availability. A key way of checking on this is to collect information on important glaciers, to determine their annual contribution to river flow.

Glacial systems work through a delicate equilibrium between snow accumulation and snow-ice melt. In the Karakorams, this balance is complicated by debris cover, which is widely present on most glacier surfaces.

Baltoro, one of the main Karakoram glaciers at about 60 km long and more than 500 square km wide, offers a spectrum of the different forms glaciers take due to temperature, precipitation and typology, as its lower part is debris-covered but its upper part is debris-free, scientists say.

This year, Mayer focused on ice melt in the lower part of the Baltoro glacier, as well as the higher “accumulation zone”, where snow collects to feed the glacier. At the conference in Islamabad, he emphasised the importance of finding out whether a glacier is “clean ice, debris-covered or snow-covered”.

Glaciers with debris, including Baltoro, pose a problem as the debris can influence the ablation process: the thicker the debris, the less the glacier melts.

Mayer discovered that debris cover on the Baltoro glacier increases towards the snout, where there is zero retreat. Because of that, “you won’t see a climate signal,” he explained.

Higher up, at around 5,800 metres, where there is no debris, the team did find ablation of around 4.5 metres. “If the debris cover is removed, you would have more than 12 metres ablation at the snout - this tells you that the Baltoro glacier is only there because of the debris cover,” Mayer said.

LACK OF FIELD RESEARCH

On the issue of “advancing glaciers” in the Karakorams, Mayer pointed out that this can be attributed to glacier dynamics - namely “glacier surges or post-surges”.

“There was no change in mass, but redistribution from higher parts to lower parts,” he said. “Do not look at area changes - you have to look at elevation changes,” he advised.

Most recent studies on the Karakorams have focused on satellite data, but Mayer argued more field studies are needed on Baltoro and other large glaciers to get a clearer picture.

“We have to go the way of mass balance measurements to understand what is happening to the large glaciers of the Karakorams,” he said.

Mass balance studies involve sticking poles into the glacier and taking field measurements. They are important because they provide a more accurate picture of the glacier’s size and health - by measuring its velocity, and whether it is sinking or rising. That is hard to determine simply from a glacier’s length and breadth.

The method requires visiting the glacier consistently for several years to take measurements, a process that is time-consuming and difficult given the remoteness of the terrain. But it has been done in the Alps and even in the Andes, where scientists have monitored glacial retreat and its effects on the hydrology of rivers.

The Karakorams are far less inhabited than other parts of the Himalayas further east. And the altitude and ruggedness of the terrain pose a challenge for researchers.

Mayer said that, to date, there is “not one single proper mass balance measurement in the Karakorams”.

On Baltoro, the Italian-supported field work is focused on determining the geometry and morphology of the glacier, as well as its dynamics and ablation. A combined analysis of these measurements will provide information on the current state of Baltoro, including its mass budget - the balance in a glacier between ice addition and melting - and meltwater production.

STORED WATER

The work of Mayer’s team will provide valuable information for Pakistan’s Water and Power Development Authority (WAPDA).

D. Hashmi, WAPDA’s representative to the scientific conference in Islamabad, said its main glacier work began in 1985. Canadian glaciologist Ken Hewitt - who coined the phrase “Karakoram Anomaly” in a groundbreaking 2005 study - worked with WAPDA and trained its experts.

WAPDA stopped monitoring the Upper Indus Basin glaciers in the 1990s. But as rivers flows are now being altered by climate change, the authority has decided it “must know the water picture”, Hashmi said.

To that end, WAPDA has recently set up a Glacier Monitoring Research Centre, which intends to conduct mass balance studies of five major Upper Indus glaciers, as well as installing new high-altitude weather stations. The six-year project is funded by the World Bank.

“The idea is to see what is happening on the ground…How have the glaciers receded? With glacier melt models we want to see, in the coming 100 years, what is the water picture of Pakistan,” said Hashmi, who works for the centre.

The Pakistani scientists may also collaborate with Ev-K2-CNR. Using modeling tools based on field and remotely sensed data, the Italian-backed team plans to produce by the end of 2014 quantitative estimates of water availability and climate change impacts on Pakistan’s agriculture and ecosystems in the coming decades.

Rina Saeed Khan writes on climate changes issues from Islamabad.

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