The Greenland Ice Sheet has lost about 9,013 gigatonnes of water ice from 1900 to 2010 — and it’s dropping mass today at an increasing rate, an international team of scientists say. From 2003 to 2010, the ice sheet lost mass at a rate more than twice the rate during the entire 20th century, a new study shows.
The findings, published in the journal Nature, provide unprecedented estimates of the shrinkage of the Greenland ice reserves and could help scientists more fully account for the world’s rising sea levels.
Researchers have been using satellite data to track the Greenland Ice Sheet’s mass loss since the 1990s, because understanding its behavior is key to understanding the effects of climate change and the consequences on rising ocean levels. But to really grasp this long-term pattern, researchers need a fuller picture of the 20th century, pre-satellites, not just a snippet of the last few decades.
“The response of the Greenland Ice Sheet to changes in temperature during the twentieth century remains contentious,” the study authors wrote, “largely owing to difficulties in estimating the spatial and temporal distribution of ice mass changes before 1992, when Greenland-wide observations first became available.”
That’s problematic, because it means that the Greenland Ice Sheet’s contribution to sea level rise has been largely overlooked for most of the 20th century — a yawning gap in the record, given that human industrial activity was significantly ramping up during this period. The start of the 20th century also marks, roughly, the decline of the Little Ice Age — an approximately four-century-long cold snap (around 1450 to 1850, depending on what part of the world you’re in) during which the Greenland Ice Sheet expanded.
So without the kind of direct satellite data we’ve had to work with since the 1990s, estimates of the sea level rise remain incomplete.
Even for the Fifth Assessment Report from the United Nation’s Intergovernmental Panel on Climate Change, “there’s blanks where they didn’t think there was enough data,” said lead author Kurt Kjaer, a glacial geologist at the Natural History Museum of Denmark.