Antarctic sea ice is hitting record levels. What does that say about global warming?



Future Tense
The Citizen's Guide to the Future
Sept. 18 2014 12:46 PM



Photo by Torsten Blackwood - Pool/Getty Images

For four days in a row this week, sea ice surrounding Antarctica has broken all-time records. But—get this—the ice is expanding, not shrinking.

It’s the third consecutive year that the icebergs that surround the continent have expanded into unseen territory. What the heck is going on? Didn’t Antarctica get the climate change memo? Isn’t polar ice supposed to be melting?

As long as humans have been keeping track, there’s never been this much sea ice surrounding Antarctica. What gives?

Figure: University of Bremen



The Antarctic (a cold continent surrounded by a warm ocean) is the geographic opposite of the Arctic (a warming ocean surrounded by cold continents). That difference, along with the fact that our economy is based on planet-warming fossil fuels, has allowed Arctic sea ice to dramatically decline in recent years, at a rate of about 4 percent per decade. At the other end of the world, Antarctic sea ice has been increasing at a fraction of that pace, less than 1 percent per decade.

It seems weird, but like this winter’s epic polar vortex outbreaks in North America, this week’s record-breaking Antarctic sea ice could be a further sign of global warming. Even though there's been more ice, the Southern Ocean is warming, not cooling. One theory says that warmer ocean waters are more effective at melting the tongues of Antarctic land ice glaciers that stick out into the sea. The resulting excess of freshwater raises the freezing point of the surrounding salt water, allowing more ice to form.

Not only is the ocean around Antarctica warming, it’s warming at a rate faster than the rest of the world’s oceans. So why is there a record amount of ice?

Figure: Zhang 2007, Journal of Climate






