Melting rate of mile-thick ice sheet ‘at fastest ever’
Dec 09 2018
"We show that although melt started to increase around the pre- to post-industrial transition, it really stayed fairly low and stable until about the 1990s", Das said. "We found a fifty percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a thirty percent increase since the 20 century alone". The study warns that if the ice sheet melting "continues at unprecedented rates", this could accelerate the already fast rate of sea level rise.
The Greenland ice sheet is up to 3 kilometres thick in places, but as it melts, the surface layer altitude is reduced.
As the ice sheet melts it becomes slightly darker, absorbing more sunlight and melting more, even if temperatures do not change, while increased melting can generate impermeable ice layers which exacerbate runoff.
And understanding how fast the ice sheet is melting is crucial for us to prepare for the impact of rising sea levels in the future, according to Professor King. "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".
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.
The year 2012, in particular, was a standout for ice melt. The team focused on these high elevations so they would be able to study records of the melting's intensity of the melting dating all the way back to the 17th century. However, the melting of ice only ramped up in the past 20 to 30 years. Instead, it forms distinct icy bands that stack up in layers of densely packed ice over time. A contemporary study portrays this enormous melt out wasn't only an irregularity juxtaposed with the last 40 years but the last 350.
Scientists then measured physical and chemical properties along the cores to determine the thickness and age of the melt layers.
The scientists combined the results from ice cores with satellite data and climate models to reconstruct melt-water runoff at lower elevations on the edge of the ice sheet that contributes to sea level rise.
Significantly, they've confirmed that the increasing melting rate is following an exponential trajectory, caused by positive feedbacks like the albedo effect, according to Dr Trusel.
"We have had a sense that there's been a great deal of melting in recent decades, but we previously had no basis for comparison with melt rates going further back in time", Osman said.
According to the study, the melting steadily and steadily until the mid-19th century, but in the 20-21 century the pace has accelerated. The satellites used to study ice sheet melting around the world haven't been around long enough to capture a complete picture of the melting process. Willis, who was not involved in the research, added "I don't know how many more nails we need".
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.