For years, scientists assumed Antarctica’s ice sheet was shrinking, but new research challenges the consensus on how global warming is impacting the world’s largest ice sheet.
National Aeronautic and Space Administration (NASA) published a new study showing that Antarctica’s ice sheet has been thickening for at least a thousand years from extra snowfall, and the south pole actually increased in mass from 1992 to 2008.
More importantly, NASA researchers found the mass gains in Antarctica mean the south pole is not contributing to global sea level rise. In fact, scientists don’t expect Antarctica to contribute to sea level rise for another 20 or 30 years.
“We’re essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of West Antarctica,” Jay Zwally, a NASA glaciologist and lead author of the study, said of past research on the south pole.
“Our main disagreement is for East Antarctica and the interior of West Antarctica – there, we see an ice gain that exceeds the losses in the other areas.” Zwally said.
For the past few years, scientists have been worried over Antarctica’s western ice sheet. The United Nations Intergovernmental Panel on Climate Change (IPCC) reported Antarctica was losing ice overall in a major 2013 report.
This set the stage for increased worries about sea level rise from the world’s largest ice sheet. Media reports of Antarctica’s imminent demise highlighted how collapsing south pole glaciers would contribute to sea level rise, making coastal cities much more vulnerable to flooding.
Subsequent studies found the Thwaites and Pine Island glaciers were collapsing and discharging large amounts of ice. In 2013, NASA found that Antarctica’s western ice sheet was facing imminent collapse.
Researchers at University of Washington estimated the western ice sheet collapse would occur over the next 200 to 900 years. Other research claimed Antarctica’s eastern ice sheet was losing ice as warm water calved it from below.
Scientists have also postulated that rapid ice loss from Antarctica caused record-high sea ice extents during the Southern Hemisphere’s winter. South pole sea ice was so thick earlier this year that scientists had trouble reaching the region by boat.
But Zwally’s research, published in the Journal of Glaciology, found Antarctica gained 112 billion tons of ice per year from 1992 to 2001 and 82 billion tons of ice per year from 2003 and 2008.
Eastern Antarctica gained 200 billion tons of ice per year from 1992 to 2008, according to Zwally’s study, outweighing ice losses from western Antarctica totalling 65 billion tons per year. This means the south pole is actually contributing to sea level declines, not sea level rises.
“The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away,” Zwally said. “But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for.”
Zwally’s team also found that snowfall over East Antarctica dramatically decreased since 1979, meaning the region’s thick ice came from ancient snowfall that hardened and thickened over the last thousand years. East Antarctica and the interior of West Antarctica have thickened by 0.7 inches per year over the last millennia — a huge gain of ice.