Greenland has melted faster than previously thought, with the rate of ice loss increasing fourfold since 2003, a new study has found.
The giant glaciers in Greenland deposit ice that is getting bigger into the Atlantic ocean, where the ice is melting. But scientists have found that the biggest loss of ice in the decade from 2003 actually occurred in the southwestern region of the island, which is mostly glacier-free.
This shows that the ice on the surface melts as global temperatures rise, causing melting streams to flow into the sea and push the surface of the sea. Southwest Greenland, which was not previously considered a source of harm to coastal cities, is set to "be the main future contributor to sea level rise," the study said.
"We know we have one big problem with the increasing rate of release of ice by several large glacier outlets," said Michael Bevis, lead author of the paper and a professor of geodynamics at Ohio State University. "But now we recognize the second serious problem: the more mass of ice will go as melt water, like the river flowing into the sea."
This research provides new evidence about the dangers posed to places of vulnerable beaches as diverse as Miami, Shanghai, Bangladesh and various Pacific islands because of the shrinking ice climate of the land-based world.
"The only thing we can do is adapt and reduce global warming further – it's too late to have no effect," Bevis said. "This will cause additional sea level rise. We watched the ice sheet reach a critical point.
"We will see faster and faster sea level rise in the future. After you reach that critical point, the only question is: How severe is that? "
This study, published in the Proceedings of the National Academy of Sciences, uses data from gravity recovery and NASA climate experiments (known as Grace) and GPS stations scattered throughout Greenland to analyze changes in ice mass.
This shows that Greenland lost around 280 billion tons of ice per year between 2002 and 2016, enough to raise sea levels worldwide by 0.03 inches per year. If all the vast Greenland ice sheets, as thick as 3 km in place, melt, global sea level will rise seven meters, or more than 20 feet, sink most of the coastal settlements.
However, the rate of loss has not been evenly distributed, with ice melting four times faster in 2013 compared to 2003. The researchers say this is driven by global temperature increases from human-caused climate change as well as the North Atlantic Oscillation, a periodic weather phenomenon that carries air warmer to western Greenland.
The fate of large Greenland glaciers in the southeast and northwest has long been seen as a key factor in global sea level rise, but research led by the State of Ohio shows that ice fields in the southwest of the island can prove a huge source of unexpected meltwater.
Scientists have gained a greater understanding of how the two massive ice masses on the planet, in Greenland and Antarctica, react to ocean warming and the atmosphere.
The loss of ice in the Arctic has tripled since the 1980s, with melting in places like Greenland and Alaska providing the biggest instigators of sea level rise while disrupting land under four million human feet.
But Antarctica is a growing concern, with the disappearance of ice at the fastest rate in history. The largest stretch of ice in the world is now losing around 219 billion tons of ice per year, a trajectory that will contribute more than 25cm to the total global sea level rise by 2070. If the entire West Antarctic ice sheet collapses, the sea level will swell around 3.5 m even for a long period of time.
"We are warming the planet, this is melting ice, and it is increasing sea level," said Richard Alley, geologist and glacier expert at Pennsylvania State University. Alley added that while there is uncertainty over future sea level rise "if large ice sheets change faster than expected, they can push faster or much faster than expected".