HUNZA (REUTERS) - A menacing black glacier is bulldozing its way down a valley in northern Pakistan, threatening to cut off a vital road link to China and blocking meltwater that could flood villages below.
Up close, the surging wall of ice almost 200m high, above Hassanabad village in Hunza district, cracked and groaned in the May sun as ice and debris fell off in big chunks.
The glacier has been advancing since last July, according to Mr Faheem Baig, a shepherd from the village next to the Karakoram Highway, 4km downstream of the glacier mouth.
"I went off with my yaks to the summer pasture far up above the glacier in May, and when I came back to get some supplies in October, the valley was completely blocked by this glacier," he told the Thomson Reuters Foundation. "The trail on the mountainside was gone and with great difficulty I made it back over the mountaintop. I had to leave my livestock behind. I couldn't believe it had moved so fast."
Mr Shehzad Baig, assistant director of the Gilgit-Baltistan Disaster Management Authority, said the Shishper glacier was on the move partly because it was located on the main Karakoram thrust line where tectonic plates are shifting.
In addition, deposits of snow on the glacier have increased due to larger amounts of snowfall in the winter months over the past five years linked to climate change, he said.
A February report on the Hindu Kush-Himalayan region from the International Centre for Integrated Mountain Development (ICIMOD) said the Karakoram and western Himalaya areas were seeing more variability and a higher probability of snowfall.
But Dr Philippus Wester from the Nepal-based ICIMOD, who led the study, said that while some glaciers in Pakistan are stable and a few are even gaining ice, they will nonetheless all start to melt in time as the planet heats up.
The report warned that more than a third of the ice in the region would melt by 2100 even if governments took tough action to limit global warming under the 2015 Paris climate agreement.
Hunza District Commissioner Babar Sahib Din, said the 15km-long Shishper glacier had surged forward 2.5km since last July, and was now advancing nearly 4m per day.
"At this rate, it will take around two years to reach the KKH (Karakoram Highway) - but we are hopeful that it will stop surging," he said.
To the left of Shishper is another glacier, Muchowar, which was once parallel but retreated 4km from 2006 to 2017, possibly sparked by rock falls linked to local mining activity.
Shishper's surge ahead means the water coming out of Muchowar as it melts in the summer cannot run down the ravine's streams, and has formed a lake in the Muchowar Valley.
A month ago, there was a danger that the glacial lake would burst, causing floods below.
But Mr Sahib Din said the risk had passed, as crevices had opened in Shishper with May's rising temperatures, enabling water to pass through into the stream.
However, there are 72 houses downstream that are at risk from sudden flooding in case bigger crevices open and the water starts flowing faster.
Villagers have been told where to evacuate, and Mr Sahib Din has set up a control room to monitor the situation.
An early warning system for glacial lake outburst floods (GLOFs) would be invaluable, he and other experts said.
The Green Climate Fund, set up to help developing countries tackle climate change, has granted US$37 million (S$51 million) to a project to reduce the risks of such floods in northern Pakistan.
Its technical adviser, Mr Abduvakkos Abdurahmanov, who works for the United Nations Development Programme (UNDP) in Pakistan, has visited Shishper glacier and believes the work is urgent.
After a bureaucratic delay of over a year as Mr Imran Khan's government settled into office, the project is finally being implemented. Sixteen valleys with threatening glaciers will be selected in the Gilgit-Baltistan region and eight in Khyber Pakhtunkhwa's mountainous districts after analysis of local vulnerabilities.
Mr Abdurahmanov said the government, the UNDP's partner on the project, had requested work be speeded up to install equipment like sensors to monitor water discharge and glacier movement.
Satellite imagery and drone mapping, meanwhile, will be used to set up early warning systems, he said. "We can calibrate the risk - but of course, it won't be 100 per cent precise," he added.
Mr Muhammad Atif, deputy director of the Pakistan Meteorological Department, noted the complexity of glacier-linked dynamics - sometimes a GLOF can be triggered by torrential rains, or a "dry flood" can occur when a lake bursts due to a temperature spike.
Mr Mohammed Ibrahim Khan, UNDP manager for the GLOF project, said lessons had been learnt from an earlier pilot project in two mountainous valleys in Chitral and Gilgit ago, financed by the UN Adaptation Fund.
They included the need for better coordination among different government departments and agencies, he said.
Besides GLOFs, the new project will address flash floods, another big problem in these mountainous areas, he added.
Other interventions include building flood prevention structures like gabion walls, and stabilising slopes by planting shrubs with deep roots and fast-growing trees such as poplars.