In Greenland, ice loss results from runoff of surface meltwater and from discharge of ice from glaciers that serve as outlets for the ice sheet, connecting it to the ocean. Accumulation results from snowfall that, compressed over years, eventually becomes ice. When runoff and discharge exceed accumulation, the result is net loss.
A paper published last week in the same journal showed that ice discharge from outlet glaciers, which includes both calving of icebergs and underwater melting, had increased by about 14 percent since the 1980s.
Most of the increase was from 2000 to 2005, and discharge rates have remained relatively consistent at this higher level since then, said the study’s lead author, Michalea King, who recently earned her doctorate from Ohio State University and will soon be a researcher at the University of Washington.
The increase in ice discharge, coupled with the trend toward increasing meltwater runoff over the past several decades, make it increasingly unlikely that Greenland will have years with a net ice gain, Dr. King said.
“It’s kind of a double whammy,” she said. “Only one of every 100 years would we expect to have mass gain.”
The new paper, which Dr. King contributed to, illustrates that point, she said. While the abnormal cold summers of 2017 and 2018 led to more ice accumulation and less surface melt runoff, “even with all of that they’re still mass-loss years,” she said, largely because of the higher glacier discharge rate.
“Mass loss is not going away anytime soon,” Dr. King said. “But of course we have control over the rate” by taking steps to mitigate climate change.
“It’s not a throw-your-hands-up kind of situation,” she said.