The Greenland ice sheet is melting faster than it has at any time in the last four centuries, and possibly faster than it has in the last 8,000 years. That’s according to new research published Wednesday in the journal Nature.
Up until this point, scientists knew that the Greenland ice sheet has been melting at a rapid clip—adding about a half-inch (13 millimeters) to global sea level rise a year. But they weren’t sure if it was melting faster now than it had been in the past, because there was simply not enough historical data to be sure.
But an international team of scientists was able to extend the historical record back to 1650, by taking core samples and looking at “melt layers,” or variations in the ice that indicate periods of melt over time. They confirmed that the current pace of melting is, in fact, far higher than it has been in any of the last several hundred years.
“It’s now increased to levels we haven’t seen before, at least in the last few centuries and probably not in the last 8,000 years,” Luke Trusel, a glaciologist at Rowan University in New Jersey and lead author of the study told DW. “The changes we’re seeing today are exceptional and unprecedented in a longer-term context.”
Trusel and his colleagues found that the rate of melting began to increase in the 1800s, shortly after the Industrial Revolution began in Europe and North America, but has intensified rapidly over the last two decades. “Our results show a pronounced 250% to 575% increase in melt intensity over the last 20 years,” compared to the melt rate in the 1700s, before the Industrial Revolution started, the researchers write.
As other researchers have pointed out, Greenland is melting in a “nonlinear” way—meaning that each one-degree increase in global air temperature can not be correlated to a standardized melt rate; instead, the ice melt is outpacing warming.
Put another way, in the past, the Greenland ice sheet might have been able to withstand 1 degree Celsius (1.8 degrees Fahrenheit) of warming without melting much faster. But as Trusel explained to DW, that same degree of warming today would cause twice as much melt, or possibly more.
If the whole Greenland ice sheet melted, it could raise global sea level by roughly 23 feet (7 meters).