Greenland’s ice sheet has passed the point of no return. Off the back of decades of warming and thawing, Greenland’s ice sheet will continue shrinking even if climate change was hypothetically stopped today, a new study has revealed.
This is what’s known as a climate tipping point. In regards to an ice sheet, it refers to the point at which its seasonal cycles are pushed out of kilter. The quantities of water replaced by snowfall each winter are no longer enough to cover the amount of water lost by thawing and outflow in the summer.
Scientists at Ohio State University studied the ice sheets of Greenland and discovered this is exactly what’s happening here.
"We've been looking at these remote sensing observations to study how ice discharge and accumulation have varied," Michalea King, lead author of the study and researcher at Ohio State University's Byrd Polar and Climate Research Center, said in a statement. "And what we've found is that the ice that's discharging into the ocean is far surpassing the snow that's accumulating on the surface of the ice sheet."
Reported in the Nature journal Communications Earth & Environment, the researchers looked at monthly satellite data that picked up on measurable changes in the gravitational field above 234 large glaciers in Greenland. This was able to give them a clear insight into the rate of ice loss and water outflow into the surrounding ocean.
Before 2000, the ice sheets would retain more or less the same mass each year between seasonable waves (as you can see in the graph above). However, the research found that the rate of net water loss started to notably increase around 2000, when the glaciers were losing about 500 gigatons of ice each year. At this point, the ice sheets continued to gradually lose mass each year as the rate of thawing was too great to be counterbalanced by replenishing snowfall each year.
“Glaciers have been sensitive to seasonal melt for as long as we’ve been able to observe it, with spikes in ice discharge in the summer,” said King. “But starting in 2000, you start superimposing that seasonal melt on a higher baseline—so you’re going to get even more losses.”
“Glacier retreat has knocked the dynamics of the whole ice sheet into a constant state of loss,” added Ian Howat, study co-author and professor of earth sciences and distinguished university scholar at Ohio State. “Even if the climate were to stay the same or even get a little colder, the ice sheet would still be losing mass.”
What happens in Greenland doesn’t stay in Greenland, either. It’s known that melting ice from Greenland is a leading contributor to sea-level rise. It’s estimated that Greenland's melting ice sheets caused the oceans to rise by 2.2 millimeters in just two months in 2019. By 2100, some estimates say it will have caused 70 to 130 millimeters of global sea-level rise. Other estimates say it could be double that. Either way, this is likely to result in flooding and widespread damage in coastal communities across the planet.