By John von Radowitz
GREENLAND glaciers are pouring water into the sea at a rate that has almost doubled in the last five years, scientists said yesterday.
The glaciers appear to be sliding faster towards the Atlantic Ocean as melting ice lubricates the rock beneath them.
Currently, the sea level around the world is rising 0.12in (3mm) per year. Taking the higher glacier speeds into account, scientists calculate Greenland is responsible for about 0.02in (0.5mm) of this increase.
The glaciers carry ice from the Greenland Ice Sheet, which is 3km thick and covers 0.66 million square miles (1.7 million sq km). If it melted completely, it would raise the global sea level 23ft (7m).
The new research indicates the amount of ice being lost from the ice sheet annually has increased from 21.6 cubic miles (90 cubic kilometres) in 1996 to 53.74 cubic miles (224 cubic kilometres) in 2005.
Due to the speed-up, the component of ice loss due to glacier flow has risen from 12 cubic miles (50 cubic kilometres) per year to 36 cubic miles (150 cubic kilometres) over the period.
Changing climate is the driving force behind the trend, say scientists. The faster moving glaciers are from the south of the continent, where average air temperature has risen 3C in the last 20 years.
Since 2000, glaciers further north have also shown signs of speeding up.
Dr Eric Rignot, who led the study, said: "The behaviour of the glaciers that dump ice into the sea is the most important aspect of understanding how an ice sheet will evolve in a changing climate. It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes.
"The southern half of Greenland is reacting to what we think is climate warming. The northern half is waiting, but I don’t think it’s going to take long."
Other scientists spoke of ancient episodes of climate change that may serve as a warning to our world.
At the start of the Eocene period 55 million years ago, temperatures rose 5C as a result of massive releases of two methane and carbon dioxide.
Another warming episode occurred three million years ago during the Middle Pliocene period. On that occasion ocean temperatures warmed by as much as 7-9C in some areas of the North Atlantic.