Water from the melt is adding to rising sea levels "more than any time during the last three-and-a-half centuries, if not thousands of years", scientists claim. Data suggests that even small changes in temperature caused exponential increases in melting in recent years - a non-linear response that points to feedback effects.
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. "Anything we can do to limit future warming, even by a little bit, is going to make a huge difference to keeping ice on Greenland and not in the ocean". If Greenland melts entirely, the seawater will increase by about 23 feet, with a damaging impact to the Earth. But more than half of the water entering the ocean comes from runoff from melted snow and glacial ice atop the ice sheet. If anyone wonders why the cores were drilled at such a high elevation - it is because the cores would contain records of past melt intensity, dating back to the 17th century.
They found that the surface of Greenland's ice sheet melts on summer days.
According to the analysis, melting on the Greenland ice sheet sped up in the mid-1800s, shortly after the onset of industrial-era warming in the Arctic. Contrary, at higher elevations, the meltwater quickly refreezes due to contact with the snowpack underneath.
While huge chunks of ice popping off Greenland's margins get more attention, the steady runoff of water from its surface is now the largest contributor to Greenland's rapid slim-down. Instead, it forms distinct icy bands that stack up in layers of densely packed ice over time. Dark bands running horizontally across the cores record the strength of the melting for a given year.
Combining results from multiple ice cores with observations of melting from satellites and sophisticated climate models, the scientists found the thickness of the annual melt layers they observed clearly tracked not only how much melting was occurring at the coring sites, but also much more broadly across Greenland. Hence, the region could be the largest contributor to the rising sea level, more than any region across the globe.
"From a historical perspective, today's melt rates are off the charts".
Dr Trusel said: "To be able to answer what might happen to Greenland next, we need to understand how Greenland has already responded to climate change".
The group analyzed ice layers spanning 350 years and found that the amount of Greenland ice sheet disintegrating was "exceptional" and that minimal but continued warming at present could inflict additional damage to the ice.
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.
Besides Woods Hole Oceanographic Institution, ice core samples were examined at the U.S. National Science Foundation Ice Core Facility in Denver, Wheaton College in Norton, Massachusetts, and the Desert Research Institute in Reno, Nevada.