A new study of satellite imagery of the Antarctic ice pack from 1979 to 2017 found the rate at which ice melted increased sixfold, from about 40 billion tons per year in 1979 to 252 billion tons by 2009. A quarter-inch rise in sea level requires about 230 billion tons of melt.
Researchers estimate half an inch of cumulative global sea level rise as a result of this increased melt with a small margin of error. Climate scientists have already predicted a global rise of up to three feet without a significant intervention in human contributions to global climate change.
Most significantly, the report raises concerns about how quickly ice is melting in East Antartica, which holds most of the continent’s frozen water, and yet hasn’t had the same level of attention paid as other regions. If East Antarctica melts faster or more extensively than expected—something this study shows in part—it could mean a faster and higher rise than currently estimated.
The Antarctic holds the total equivalent of about 188 feet of sea-level rise in its ice—170 feet are in East Antarctica alone.
The Antarctic receives about 2.1 trillion tons of snowfall a year, the snow equivalent of about a quarter-inch of global sea level. Decades ago, this snowfall roughly balanced out ice that melted at the edges of the continent’s snowpack and loss from glaciers descending slowly into the ocean.
However, while snowfall has remained roughly constant over this period, researchers found, the increased melting resulted in that roughly half an inch of global sea level rise. They conclude this is due to the presence of warm salty water around the edges of the Antarctic continental shelf which “vigorously melts the ice shelves, reduces buttressing of the glaciers, and allows them to flow faster.”
The study, which appeared on Jan. 14 in the Proceedings of the National Academy of Science, developed by researchers in the U.S. (at UCS and NASA’s JPL), the Netherlands, and France, extended previous analysis of satellite imagery, dating from 1979 to 2017. The authors looked at changes in 18 regions and across dozens of glaciers.
The study’s results match up with the results of work published in June 2018 in Nature that involved examining two dozen sets of measurements of Antarctic ice loss, and which produced a consensus annual loss in of 219 billion tons each year from 2012 to 2017—about a fivefold increase rather than the new report’s sixfold bump. That study found a cumulative global sea level contribution of 0.3 inches with a wide error of margin of ±0.15 inches.
One of the authors of the Nature study told the Washington Post, “More work is needed to reconcile these new estimates.”