The glaciers that are actually GROWING, not shrinking: Climate change not as catastrophic as scientists first thought

By Daily Mail reporter  27 January 2011

Climate change may not be as catastrophic for Greenland's icecaps as scientists first thought after researchers found hotter summers may actually slow down the flow of glaciers.

Increased melting in the warmer summer months is causing 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.

This is because in hot conditions there is initially so much melt-water that it runs off into channels below the ice, thereby decreasing the lubricating layer which sits on top of the ice sheets and causes melting over a much larger surface area.



Scientists today said Himalayan glaciers are actually growing and not shrinking.

Half of the ice flows in the Karakoran range of the mountains are advancing and not retreating, researchers announced in the first major study since a 2007 United Nations report warned the glaciers would melt by 2035.

The new research, carried out by scientists at the University of California and the University of Potsdam, concluded that global warming is not directly responsible for how glaciers fare.

Dr Bodo Bookhagen told the Daily Telegraph that 'there is no stereotypical Himalayan glacier' and said the UN's report 'lumps all Himalayan glaciers together'.

Owing to this, the acceleration of melting appears to stall early on in hot summers, whereas it does not in cool ones.

The findings, reported in the journal Nature, 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 7 metres if it were to melt completely.

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

Some of the ice loss has been attributed to the speed-up of glaciers due to increased surface melting. 

Each summer, warmer temperatures cause ice at the surface of the sheet to melt.

Temperature controlled: The acceleration of melting ice appears to stall early on in hot summers, whereas it does not in cool summers

This water then runs down a series of channels to the base of the glacier where it acts as a lubricant, allowing the ice sheet to flow rapidly across the bedrock toward the sea.

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

'It had been thought that more surface melting would cause the ice sheet to speed up and retreat faster, but our study suggests that the opposite could in fact be true,' said Professor Andrew Shepherd from the University of Leeds School of Earth and Environment, who led the study.

'If that's the case, increases in surface melting expected over the 21st century may have no affect on the rate of ice loss through flow. However, this doesn't mean that the ice sheet is safe from climate change, because the impact of ocean-driven melting remains uncertain.'

Greenland's ice contains enough water to raise sea levels by seven metres if it were to melt completely

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, slowdown 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.

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

Despite their findings, however, the researchers were keen to emphasise that the ice sheet is 'not safe from climate change'.

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