Antarctica’s ice melt is inconsistent, new analysis shows

Antarctic ice is melting, contributing massive amounts of water to the world’s oceans and causing them to rise – but that melting isn’t as linear and consistent as scientists previously thought, a new analysis of 20 years of satellite data shows.

The analysis, based on gravitational field data from a NASA satellite system, shows that Antarctica’s ice is melting at different rates every year, meaning the models scientists use to predict upcoming sea-level rise may also need to be adjusted.

“The ice sheet isn’t constantly changing – it’s more complicated than a linear change,” said Lei Wang, assistant professor of civil engineering, environmental and geodetic engineering at Ohio State University and lead author of the analysis. “The change is more dynamic: the speed of the melt changes over time.”

The research is published in Geophysical Research Letters and presented at the fall meeting of the American Geophysical Union in December.

The researchers’ analysis is based on data from NASA’s GRACE (Gravity Recovery and Climate Experiment), a two-satellite mission that measures changes in the world’s oceans, groundwater and ice sheets.

Models predicting sea level rise are generally based on the assumption that ice is melting at a constant rate from the world’s largest ice fields in Antarctica and Greenland.

But this analysis found that because the ice mass on the Antarctic Ice Sheet changes depending on the season and year, these projections are not as reliable as they could be. For example, extreme snowfall in a year can increase the amount of ice in Antarctica. Changes in the atmosphere or the surrounding ocean can diminish this for another year.

Overall, Wang said, ice volume in Antarctica is declining. But a graph of the decline in a line graph would have peaks and troughs depending on what happened in a given period.

To understand those changes, Wang and the other researchers evaluated data about the gravitational field between the satellites over Antarctica and ice on the continent. Changes in the mass of the ice – either increasing due to large snowfall or decreasing due to melt – change that gravitational field.

For example, from 2016 to 2018, the ice sheet in West Antarctica grew a bit due to massive snowfall. During the same period, the ice sheet in East Antarctica shrank due to melting.

“I’m not saying that Antarctic ice melting isn’t an acute problem – it’s still very acute,” Wang said. “All of Antarctica is losing mass very quickly. It’s just a time-scale problem and a rate problem, and our models predicting sea level change should reflect that.”