By Stephanie Pappas, Live Science Contributor | December 5, 2018 02:00pm ET
Each summer, large rivers emerge on the surface of Greenland, swiftly sending meltwater from the ice sheet into the sea.
Credit: Sarah Das/Woods Hole Oceanographic Institution
Greenland is melting faster today than it has at any time in the last 350 years, and probably much longer, new research finds.
Surface melt from the icy island has increased 50 percent in the last 20 years compared with the early 1800s, before the industrial era, researchers report today (Dec. 5) in the journal Nature. The runoff alone is now contributing about a millimeter to the global average sea level per year, said study co-author Sarah Das, a glaciologist at Woods Hole Oceanographic Institution.
Scientiststracking Greenland’s ice by satellite and on the ground have seenincreasingly dire ice loss. Greenland loses ice both when icebergs calve off glaciers and when ice on the surface melts and flows to the sea as water. The meltwater flow is how themajority of the ice vanishes, and that’s what Das and her colleagues focused on.
The researchers analyzed ice cores drilled from the high-elevation center of Greenland, where each year’s snowfall melts a little bit and refreezes before being covered by a new season’s worth of snow. This layered pattern allows researchers to estimate how much melt took place each year, going back about 350 years. The team was then able to use modern, precise measurements of melt and correlate those measurements with the pattern seen in the ice cores, which allowed them to estimate what melt at lower elevations across the island would have looked like in each year recorded in the high-elevation cores. [Images: Greenland’s Gorgeous Glaciers]
The numbers weren’t good. The last two decades of melt show an increase in the rate of melting of 250 percent to 575 percent compared with the preindustrial baseline from before the mid-1800s. 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. Over the 20th century alone, the runoff of meltwater increased 33 percent.
“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. “So, it’s really been in the last couple of decades that we’ve seen this exceptional rise.”