We live in an era of accelerating climate change, and the Greenland ice sheet is Exhibit A. A rapid meltdown is occurring due to rising temperatures, and the rate of loss is quickening.
A new paper published on Monday in the Proceedings of the National Academy of Sciences shows after decades of near equilibrium, Greenland began losing ice in the 1980s and it’s accelerated sixfold since then. That has sped up its contribution to sea level rise and raises concerns about what the future holds.
Our understanding of what’s happening to Greenland’s ice today has largely been confined to past few decades of detailed satellite imagery. But older data has been out there waiting to be mined, and the new analysis does just that. It draws on Landsat data that began pouring in from satellites in orbit above Earth in 1972.
“Over the entire period, even though we have more and better data now than in the 1970s, we are able to construct a robust, comprehensive and very precise record of mass change,” Eric Rignot, an ice researcher at the University of California, Irvine who worked on the study, told Earther.
That represents a big leap back in time since other satellite data, measuring the height of glaciers and only runs back to the early 2000s. Ellyn Enderlin, an ice sheet researcher at Boise State who wasn’t involved in the research, likened the shorter data sets to “capturing ice sheet weather.” She told Earther the new study, which incorporates older satellite data with the newer data, paints a richer picture of how the Greenland ice sheet’s mass has changed over time. Unfortunately it’s not a pretty one.
The results show that Greenland’s mass stayed mostly within its natural range of variability in the 1970s before slimming down steadily in the 1980s and then more rapidly in the next few decades. The biggest losses have come in the northwest, which has shed 1,578 gigatons of ice into the sea. That’s enough to fill Lake Erie more than three times over, though it represents a small fraction of all the ice stored in that region, which would raise sea levels more than four feet if melted. Add in the rest of the island’s ice, and you have enough water to raise sea levels 24 feet. The research shows all parts of Greenland are now losing ice and that the rate of loss has sped up. It doesn’t mean we’ll be canoeing through New York or Shanghai tomorrow, but the speed up shows the ice sheet is definitely feeling the impacts of climate change.
“The mass loss has increased six fold since the 1980s, which shows that the response of the ice sheet to climate warming is very rapid and very strong,” Rignot said.
That portends a more worrisome meltdown as ocean and air temperatures keep rising. Indeed, this year has already seen a few signs of surface melt in early April well ahead of schedule, due to temperatures rising up to 36 degrees Fahrenheit above normal for this time of year. While it’s only one year (and the ice sheet is still gaining mass at this point), it portends the bigger changes afoot in the Arctic, the fastest warming region on Earth.
In addition to raising sea levels, researchers are also concerned about the massive influx of freshwater into the North Atlantic. Recent research suggests that the melt could mess with ocean currents, which could in turn have a ripple affect on the weather. It points to the need for a comprehensive monitoring effort to know what’s going on at the top of the world as things get more out of whack.
“We can’t look at one glacier or even five glaciers, and say ‘this is how the ice sheet will change going forward,’” Enderlin said. “We need to keep this broad focus.”