Antarctica has had a busy few weeks in the news. Yesterday, climate scientists announced that west Antarctica’s ice sheet could collapse into the sea if the melting oceanside glaciers disappear. The study, which heightens fears of the region's instability, comes on the heels of a NASA report that found ice sheets in eastern Antarctica are actually growing. While these findings may seem contradictory at first glance, it is a perfect showing of how climate change can have different effects in different locations.
First things first: If global warming is melting glaciers in west Antarctica, how can more ice appear in the east? While “global warming” is often used to mean “climate change,” in reality it’s more of a symptom than a synonym. Basically, global warming is to climate change as a square is to a rectangle: All squares are rectangles, but not all rectangles are necessarily squares.
When scientists refer to global warming, they specifically mean the phenomenon of global temperatures rising due to high levels of greenhouse gases in the atmosphere. On the other hand, NASA defines “climate change” as any long-term change in climate (whether increasing or decreasing temperatures, extreme storms or crippling droughts) on regions of Earth.
Though many scientists agree that warmer oceans are a big reason why the glaciers in West Antarctica’s Amundsen Sea are melting so rapidly, that’s a different process than global warming. In fact, the reason parts of Antarctica are gaining ice is because of climate change, just not the change that is happening now.
About 10,000 years ago, Antarctica began getting more snow, which compacted into ice over thousands of years, NASA glaciologist Jay Zwally said in a statement. Antarctica got so much snowfall during the Ice Age that its ice sheets are still growing thanks to the colder temperatures and increased moisture from millennia ago.
So what’s so worrying about the western glaciers melting if Antarctica is gaining more ice than it loses every year? After all, according to the NASA study, snowfall over the ice sheets in east Antarctica and the western interior adds hundreds of billions of tons of ice every year, enough to outweigh the ice lost by melting glaciers. The report even suggests that the ice sheets may actually reabsorb some of the lost glacial ice.
But all is not well. According to the report, east Antarctica gained 112 billion tons of ice each year from 1992 to 2001, but that rate dropped to an annual 82 billion tons from 2003 to 2008. And the Potsdam Institute’s study shows that the rapid pace of melting glaciers in the Amundsen Sea could still have dire consequences for the western ice cover.
“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—I don’t think there will be enough snowfall increase to offset these losses,” Zwally, who lead the study, said in a statement.
In this case, the problem comes down to warming oceans and Antarctica’s topography. As NASA sea ice scientist Walt Meier tells Marcy Kreiter for International Business Times, Antarctica’s sea ice cap was once a solid sheet of ice, “like a fortress.”
“The sea ice cap...now is fragmented into smaller floes that are more exposed to warm ocean waters,” Meier tells Kreiter. “The ocean could only attack it from the sides. Now it’s like the invaders have tunneled in from underneath and the ice pack melts from within.”
West Antarctica’s ice floes are not only melting: They could take the rest of the ice cover with it, according to a new study published Monday in the Proceedings of the National Academy of Sciences. If the glaciers in the Amundsen Sea completely melt, there are few natural features that would keep the rest of West Antarctica’s ice sheet from collapsing into the ocean, Chris Mooney reports for The Washington Post.
“We showed that there is actually nothing that stops it,” study author and climate scientist at the Potsdam Institute for Climate Impact Research Anders Levermann tells Mooney. “There are troughs and channels and all this stuff, there’s a lot of topography that actually has the potential to slow down or stop the instability, but it doesn’t.”
Levermann and his team used a computer model to simulate what might happen to the west Antarctica ice sheet if current melting rates stay the same. Because the floor underneath the Amundsen Sea’s glaciers gets deeper as it goes inland, warming ocean temperatures could melt underneath, thinning out the ice sheet and causing it to break up faster. If this did happen the melted ice could cause global sea levels to rise more than 10 feet.
Now, this isn’t going to happen in a matter of months or even in the next few years: Mooney reports that the study simulated what might happen over hundreds to thousands of years but more work is necessary to say for sure.
“I don’t want to say it’s quicker, but it’s much more likely that it’s faster than these thousands of years, than [that] it’s slower,” Levermann tells Mooney.
Both studies may cover the same continent, but their main subjects are still thousands of miles apart. The east Antarctica ice sheet may be thickening, but that doesn’t mean the glaciers in the Amundsen Sea aren’t in danger of melting away. When it comes to climate change, the problems are rarely as straightforward as they might sometimes seem.