Scientists’ cool discovery

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WARMER summers may not be as catastrophic for the environment as previously feared - and may actually slow down the flow of glaciers, according to new research by Sheffield University scientists.

Increased melting in warmer years causes the internal drainage system of the ice sheet to ‘adapt’ and accommodate more melt-water, without speeding up the flow of ice toward the oceans.

The findings from a project involving the universities of Sheffield, Leeds, Edinburgh and Brussels have important implications for future assessments of global sea level rise.

The Greenland ice sheet covers roughly 80 per cent of the surface of the island and contains enough water to raise sea levels by seven metres if it were to melt completely.

Rising temperatures in the Arctic in recent years have caused the ice sheet to shrink, prompting fears it may be close to a ‘tipping point’ of no return.

Summertime acceleration of ice flow has proved difficult for scientists to model, leading to uncertainties in projections of future sea level rise.

The researchers used satellite observations of six landlocked glaciers in south-west Greenland, acquired by the European Space Agency, to study how ice flow develops in years of markedly different melting.

Although the initial speed up of ice was similar in all years, slow down occurred sooner in the warmest ones.

The authors suggest that in these years the abundance of melt-water triggers an early switch in the plumbing at the base of the ice, causing a pressure drop that leads to reduced ice speeds.

The behaviour is similar to that of mountain glaciers, where the summertime speed-up of ice reduces once melt-water can drain efficiently.

Dr Edward Hanna from Sheffield University’s Department of Geography, said: “Our study shows the relationship between melting and flow of large ice masses is more complex than has sometimes been appreciated.

“Perhaps surprisingly, it has shown increased ice melt does not always result in greater movement of an ice mass but sometimes the opposite occurs.”

Professor Andrew Shepherd, who led the study, said: “It had been thought more surface melting would cause the ice sheet to speed up and retreat faster, but our study suggests the opposite could in fact be true.

“However, this doesn’t mean the ice sheet is safe from climate change.”