Antarctica is losing six times more ice annually than it was 40 years ago, according to a study published Monday in Proceedings of the National Academy of Sciences. The acceleration in Antarctic ice melt, which is linked in part to anthropogenic climate change, has caused global sea levels to rise by more than half an inch since 1979.
"That's just the tip of the iceberg, so to speak," lead author Eric Rignot, a NASA research scientist and UC Irvine professor, said in a statement. "As the Antarctic ice sheet continues to melt away, we expect multi-meter sea level rise from Antarctica in the coming centuries."
Rignot and his colleagues calculated annual rates of Antarctic ice loss from 1979 to 2017 using several lines of evidence, including NASA’s Landsat program. This constellation of Earth-observing satellites dates back to the 1970s, making it possible for the team to observe space-down views of 176 Antarctic drainage basins over four decades.
Aerial imagery from NASA’s Operation IceBridge, which has been flying research planes over the polar continent since 2009, also helped the researchers estimate annual snowfall, wind erosion, ice sheet thickness, and glacier discharge levels with high accuracy.
By combing over this data, the team found that Antarctica has been releasing significantly more ice into the oceans with each passing decade. During the 1980s, for instance, ice loss averaged around 40 gigatons per year. From 2009 to 2017, that average spiraled up to an annual loss of 252 gigatons.
Over the past decade, about 63 percent of the continent’s total ice loss came from West Antarctica. East Antarctica made up 20 percent of the total, while the Antarctic Peninsula was responsible for the remaining 17 percent.
The biggest driver of ice loss is circumpolar deep water (CDW), a mass of warm extra-salty water that has been increasingly pushed under floating ice shelves by stronger polar westerly currents. This water rapidly melts ice sheets and tidewater glaciers from below, and is expected to continue exacerbating ice-melt off the continent.
The connection between human-driven climate change and Antarctic ice loss is complicated, and scientists are still working to nail down the nuances. That said, greenhouse gas emissions and ozone depletion are linked to the shifts in polar westerlies seen over the past half-century. That change has exposed more vulnerable Antarctic ice shelves to CDW.
The research reveals “a mass loss during the entire period [of 38 years] and a rapid increase over the last two decades in parts of Antarctica closest to known or suspected sources of CDW,” the researchers said in the paper.
“In the decades to come, it is likely that sea level rise from Antarctica will originate from the same general areas,” theY noted, adding that the trend “could contribute multimeter sea level rise with unabated climate warming.”
Get six of our favorite Motherboard stories every day by signing up for our newsletter.