The rate at which glaciers are melting in the Himalayas is being significantly accelerated by lakes already formed by glacial retreat, according to Scots researchers.

Their study concluded the glaciers that have flowed into the lakes in recent decades are retreating and thinning much more quickly than others in the region.

Previous studies have shown not all glaciers melt in the same way and researchers Dr Owen King and Dr Tobias Bolch, of the School Of Geography And Sustainable Development at St Andrews University, wanted to investigate the unanswered questions posed previously.

Mr King said: “Earlier pieces of work tended to show glaciers that flowed into lakes receded at a faster rate than the glaciers that didn’t.”

The scientists used declassified US Hexagon spy satellite imagery, data from the Shuttle Radar Topographic Mission in 2000 and information from modern satellites to examine the relationship between glaciers and glacial lakes since the 1970s.

Examining the different data sets, the research team found the ice front retreated at more than twice the rate of glaciers that do not flow into lakes.

Mr King added: “We have identified in the latest time period glaciers with lakes retreated nearly 30 metres (98ft) a year on average.

“Further enhanced mass loss is very likely should the increases in the total number and area of glacial lakes continue.”

The glaciers are responsible for as much as 30 per cent of the ice loss in different parts of the mountain range, despite comprising just 10 to 15 per cent of the total glacier population.

The behaviour of glaciers provides the clearest indication of climatic change in high mountain regions, with long-term atmospheric warming believed to have caused the recession of glaciers across the Himalayas.

But why the glaciers that flow into lakes have a higher rate of recession has still to be determined.

Mr King said: “That needs further work. “Easily recognisable mechanisms that could explain the loss is that they can produce icebergs and carve out the big outlet glaciers around Greenland and Antarctica so big chunks of ice fall off the front of the lake, terminating glaciers.  

“The lake is warmer than the ice so it melts.”

Meltwater from glaciers in this region sustains the flow of river systems on which hundreds of millions of people depend for their basic needs.

Not all the meltwater instantly drains to downstream catchments and thousands of glacial lakes have developed and continue to expand high in the Himalayas.

Until this study, the influence of the lakes on glacier behaviour in the mountain range has not been thoroughly investigated, despite the rapid increase in lake area and number.

The results show glacier mass reduction has happened since at least the 1970s and has accelerated this millennium.

Glaciers in contact with glacial lakes showed a significantly higher decrease in mass and are therefore likely to be driving the accelerating loss from the region.

Mr King, who has visited the region four times in the last four years, has seen the visible difference.

He said: “The scale of ice loss is really obvious to see. Not just for glaciers that have lakes in front of them, but also those that don’t have lakes leave behind signs of how big they used to be and these landforms are a record of where the glacier was in colder times.

“Now you can see glaciers have thinned by up to a 100 metres.”

Measuring the changes in the Himalayas, which has many of the world’s highest mountains, was no easy feat because of the sheer scale of the landscape.

Mr King added: “Because the mountains are so steep and big, the weathering rates are really high, so there’s a lot of rock and avalanche debris that works its way down the glaciers. Once that debris gets thick enough, it can act as a bit of a blanket on the glacier it falls on that can protect the ice underneath, so the front generally doesn’t recede as much.”

The change the team documented is the height change in the glacier rather than the change in length.

Mr Bolch said: “Our results have important implications for future projections of ice loss from the region because the interaction of glaciers and glacial lakes has not previously been considered in future glacier ice loss estimates.”