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The Greenland shield is melting at a record pace - the scientists

07 December 2018

The loss of ice from Greenland is one of the key drivers of rising global sea levels.

Greenland's ice sheet is now melting at a rate that is "off the charts" compared with the last 350 years, a new study by scientists from Woods Hole Oceanographic Institution (WHOI) has warned.

Human adjustment of the atmosphere began with the Industrial Revolution of the mid-19 century.

The report reveals that the ice in Greenland is melting at a rate much faster than anything seen over the last couple of centuries and maybe even the last millennium, reports DR Nyheder. This means that the sea level could rise sooner and faster than previously assumed. Greenland loses ice both when icebergs calve off glaciers and when ice on the surface melts and flows to the sea as water. The melting and freezing cycle also makes ice below the surface less permeable, so more runoff is shunted to the ocean rather than trickling down into the ice sheet.

The research team found out how intensely Greenland ice has melted in past centuries using a drill the size of a traffic light pole to extract ice cores from the ice sheet and a nearby coastal ice cap. The scientists drilled at these elevations to ensure the cores would contain records of past melt intensity, allowing them to extend their records back into the 17 century. "We demonstrate that Greenland ice is more sensitive to warming today than in the past - it responds non-linearly due to positive feedbacks inherent to the system".

Researchers say that if the Greenland ice sheet melting continues at "unprecedented rates" - which they attribute to warmer summers - it could accelerate the already fast pace of sea level rise.

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Meltwater slides off Greenland's massive ice sheet into the ocean during hot summer days. Instead of escaping the ice sheet, the short-lived meltwater forms icy bands that stack up layers of densely packed ice over time.

Scientists at four ice core labs in the United States measured physical and chemical properties along the cores to determine the thickness and age of the melt layers. Dark bands running horizontally across the cores, like ticks on a ruler, enabled the scientists to visually chronicle the strength of melting at the surface from year to year. This threatens cities such as London and Venice and entire nations such as the Maldives, which within decades could be swallowed by the rising level of the sea.

Sarah Das, a glaciologist at Woods Hole Oceanographic Institution (WHOI) and co-author of the study notes that from a historical perspective, today's ice melt is "off the charts". The researchers found that the rate translated to a 50-percent increase in the runoff of meltwater into the sea compared with the preindustrial era.

Satellite methods to understand melting rates have only been around in recent decades, so the ability to go back further in time was important. Now, even a very small temperature change in the region can cause huge spikes in ice sheet melting, according to the study.

Ice sheet melting began to increase on the 3,000-metre thick ice sheet soon after the Industrial Revolution in the 1800s but was the most extensive in 2012.

In the wake of October's dire report from the UN Intergovernmental Panel on Climate Change warning that civilization has just more than a decade to stave off climate catastrophe, Thursday's report spells more bad news for the planet, especially the millions of people living near the world's oceans.

The Greenland shield is melting at a record pace - the scientists