Melting glaciers will only have a 'minor' role in future sea level rises, scientists claim



Scientists feared water which trickles down through ice could speed up the movement of glaciers as it acts as lubricant between the ice and the ground

However, they discovered this process will probably only have a minor role in sea level rises compared to iceberg carving and surface melt

Lubrication will add less than five per cent of the total projected contribution to sea level rises from the Greenland ice sheet

The lubricating effect of melting water on glaciers will have only a ‘minor’ role in future sea level rises, according to new research.



Scientists had feared that melt water which trickles down through ice could dramatically speed up the movement of glaciers as it acts as a lubricant between the ice and the ground it moves over.



But a team from the University of Bristol found it is likely to have a minor role in sea level rises, compared with other effects such as iceberg production and surface melt.



The lubricating effect of melting water on glaciers will have only a 'minor' role in future sea level rises, according to new research

Results from computer modelling - based on fieldwork observations in Greenland - revealed that lubrication will add less than five per cent of the total projected contribution from the Greenland ice sheet.



Some simulations found the lubricating effect could even have a negative impact on sea level rise - leading to a lowering of sea level when the other major factors were ignored.

Sarah Shannon, from the University of Bristol, was lead author of the research, which was published in Proceedings Of The National Academy Of Sciences Of The United States Of America (PNAS).

‘This is an important step forward in our understanding of the factors that control sea level rise from the Greenland ice sheet,’ Dr Shannon said.



Scientists had feared that melt water which trickles down through ice could dramatically speed up the movement of glaciers as it acts as a lubricant between the ice and the ground it moves over

‘Our results show that melt-water-enhanced lubrication will have a minor contribution to future sea level rise. Future mass loss will be governed by changes in surface melt water runoff or iceberg calving.’



WHAT DID THE RESEARCHERS FIND?

Scientists had feared that melt water which trickles down through ice could dramatically speed up the movement of glaciers by acting as a lubricant between the ice and the ground. The researchers found that this is not likely to be the case because a lot of the water runs off through channels meaning it does not act as a lubricant. Therefore, it is likely to have a minor role in sea level rises compared with other effects, such as iceberg production and surface melt. Lubrication will add less than five per cent of the total projected contribution to sea level rises from the Greenland ice sheet.

Previous studies of the effects of melt water on the speed of ice movement assumed the water created cavities at the bottom of ice masses.

These cavities filled with water which lifted the ice slightly and acted as a lubricant, speeding up flow.



The theory led scientists to think that increased melt water would lead directly to more lubrication and a consequent speeding up of the ice flow.



But the Bristol study took into account observations indicating larger amounts of melt water may form channels beneath the ice that drain water away.



This would reduce the water's lubricating effect.



The research concluded that the effect on sea level is small, regardless of whether melt water increases or decreases. Dr Shannon added:



‘We found that the melt water would lead to a redistribution of the ice, but not necessarily to an increase in flow.’

The findings are part of research undertaken through the European-funded ice2sea programme.

Results from computer modelling revealed that lubrication will add less than five per cent of the total projected contribution to sea level rises from the Greenland ice sheet

Earlier research from ice2sea found changes in surface melting of the ice sheet will be the major factor in sea level rise contributions from Greenland.



Professor David Vaughan, ice2sea co-ordinator based at the British Antarctic Survey in Cambridge, said: ‘This is important work but it's no reason for complacency. While this work shows that the process of lubrication of ice flow by surface melting is rather insignificant, our projections are still that Greenland will be a major source of future sea-level rise.

