Up north, the sea ice loss in the Arctic is exactly what you would expect in a warming world. 2012 was a record-low year for Arctic sea ice in the satellite record, and 2014 was the sixth lowest.
But in the Antarctic, sea ice has been growing year over year. This is in contrast to the ice on Antarctic land, which appears to be shrinking faster than previously estimated. The dichotomy suggests that something much more complicated than “warming equals melting” is occurring, and scientists say that more research is needed to understand the observations.
One possible explanation for the growing sea ice extent is that weather patterns around the Antarctic may be pushing more cold, continental air over the ocean, spurring the formation of more sea ice.
Another possibility actually includes the melting of the ice over Antarctica itself — as the land ice melts, it could be flushing large amounts of fresh water, which freezes faster, into the ocean.
“There hasn’t been one explanation yet that I’d say has become a consensus, where people say, ‘We’ve nailed it, this is why it’s happening,’” said Claire Parkinson, a senior scientist at NASA’s Goddard Space Flight Center. “Our models are improving, but they’re far from perfect. One by one, scientists are figuring out that particular variables are more important than we thought years ago, and one by one those variables are getting incorporated into the models.”
When it comes to comparing the Arctic and the Antarctic, it’s probably best not to draw conclusions from their differences. “Some people have looked at the Antarctic increasing trend and use that to suggest that global warming isn’t happening, or that the increase in the Antarctic is offsetting the decrease in the Arctic and that’s simply not true,” says Walt Meier, a research scientist at the NASA Goddard Space Flight Center, in a video on the record extent. “If you look at the magnitudes of the changes we’re seeing in the wintertime, the Arctic is decreasing about twice as fast as the Antarctic is increasing.”
This year’s record extent will likely prompt new research on the difference between the North and South poles, and for good reason, according to Meier. “They’re more sensitive to climate change, and therefore they’re the regions that we see the biggest effects of climate change so far,” says Meier. “They’re kind of the canary in a coal mine of global warming.”