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The Antarctic Peninsula, shown here photographed from a NASA survey plane, is losing more ice than it's gaining, but ice on the rest of the continent is increasing.
This is strange news to many scientists. Most research to date assumes Antarctica's ice sheet is melting and contributing to global sea level rise.
But the authors of the new study, published Oct. 29 in the Journal of Glaciology, found that Antarctica had a net increase of 112 billion tons of ice per year from 1992 to 2001.
Between 2003 and 2008, however, that rate slowed to gains of 82 billion tons of ice per year.
It's difficult to imagine that much ice, but it would be enough to cover the state of Rhode Island about 85 feet deep every year in pure form. (About 4,450 Rhode Islands can fit inside Antarctica, spreading out all of those ice gains, which is probably why scientists haven't noticed them until now.)
Climate deniers shouldn't welcome the news. While the continent is still gaining ice overall, the Antarctic Peninsula and parts of Western Antarctica are melting at faster rates, leading to net ice losses there. And researchers warn climate change is likely to continue slowing and reversing ice gains in the coming decades.
"If the losses of the Antarctic Peninsula and parts of West Antarctica continue to increase at the same rate they've been increasing for the last two decades, the losses will catch up with the long-term gain in East Antarctica in 20 or 30 years," lead author Jay Zwally said in a NASA press release. "I don't think there will be enough snowfall increase to offset these losses."
Jay Zwally/Journal of Glaciology
Net ice losses are on the left side of the legend, and ice gains are on the right. As a whole, Antarctica was amassing ice over the last two decades.
In order to calculate how much ice the continent was gaining and losing, the researchers used satellites to measure Antarctica's altitudes. They they combined this data with information from ice cores, which are a record of snow accumulation over the last 10,000 years.
Altitudes can be really hard to measure. They can change over time, and it can take a long time to record an area as big as Antarctica.
Glaciologist Ben Smith from the University of Washington in Seattle, who wasn't involved in the NASA study, said in the press release how challenging it can be to measure "the small changes in ice height happening in East Antarctica." Smith also said we still need to precisely record snow accumulation in order to fully understand the nature of the net ice gains and losses.
Despite the results of the new study, global sea levels continue to rise - so the ice melt driving that phenomenon must be coming from somewhere other than Antarctica. The 2013 Intergovernmental Panel on Climate Change (IPCC) report credits Antarctica with 0.27 millimeters of sea level rise per year, but the study reports that the ice gains on the continent could actually be reducing the rise.
"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 in the press release. "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."
This study is good news for now, but the seas will likely keep rising if nothing is done to curb the climate change that's driving the global ice melt.