Antarctic sea ice reaches highest maximum on record

Credit: NASA's Scientific Visualization Studio/Cindy Starr

Monday, October 13, 2014, 3:35 PM - On September 22, 2014, the amount of sea ice surrounding the continent of Antarctic reached its maximum for the year, which also turned out to be the highest extent we have ever recorded there, even in decades of monitoring. Contrary to some inevitable claims, though, this record extent is anything but good news.

The amount of sea ice at Earth's poles grows and shrinks each year. In the Arctic, sea ice reaches a maximum extent sometime in March, after the north has gone through fall and winter, and then the extent drops through the spring and summer, reaching a minimum sometime in mid-to-late September. In the southern hemisphere, sea ice surrounding the Antarctic continent behaves roughly opposite, reaching a minimum in March and a maximum in September. This pattern repeats year after year, but ever since the 1970s, we've noticed two trends - Arctic sea ice minimums and maximums show a steady and alarming decline, while Antarctic sea ice shows a modest growth trend.

This past September, just as the sea ice in the Arctic Ocean reached its lowest extent for the year - the sixth lowest sea ice minimum on record - Antarctic sea ice was reaching a remarkable maximum. Not only was this the largest maximum extent we've ever seen there, but this was the first time the sea ice reached an extent of 20 million square kilometres since long-term record keeping for Antarctic sea ice began. In the image above, the red line represents the average maximum extent between 1979-2014.

CLICK BELOW TO WATCH: "The Arctic and the Antarctic ... are like the canary in the coal mine for global warming."

With climate scientists so concerned about melting sea ice, this new record maximum sea ice extent around Antarctica may seem like good news, but unfortunately it's not.

If sea ice in the Arctic Ocean was growing to extents that were larger than we've ever seen, that would be a good thing (unless it grew too large, in which case it might suggest we were entering a new ice age). This is because any growth in Arctic sea ice tends to represent the freezing of water that's already part of the system. Very little, if any, is being added, thus the ice is forming because it happens to be cold enough there to freeze the sea water.

The increases in Antarctic sea ice apparently represent something quite different. Although scientists are still studying what's going on there to fully understand what's happening, it seems that the increase in Antarctic sea ice comes from a combination of at least two factors - fresh water melting from Antarctic land ice and stronger winds blowing around the continent.

As volcanic hot-spots and warm sub-surface ocean currents pick away at Antarctica's glaciers, there is a lot of fresh water pouring off these glaciers into the waters surrounding the continent. Since fresh water is less dense than salt water, it doesn't mix in to the ocean water very well and much of that meltwater instead floats there in a layer on the surface. This fresh water is only a few degrees above freezing, at the most, so it doesn't take much for the frigid temperatures and winds to refreeze it.

At the same time, researchers have shown that the effects of global warming could be strengthening of the southern polar vortex - the clockwise circulation of winds that surrounds Antarctica. With these stronger winds pushing the ice along, it would also be pushed further away from Antarctica, due to the Coriolis Effect. 

Thus, the greater amount of ice forming from the refreezing of fresh meltwater and more of that ice being pushed further away from land by the winds would result in an overall wider extent of ice.

There is no balance between northern and southern sea ice, though. The increases in Antarctic sea ice - regardless of them being at a record maximum this year - are minor compared to the losses of Arctic sea ice, and as a result, global sea ice extent also shows an overall decline.

Credit: James Hansen

These 'anomalous' effects around Antarctica weren't entirely expected as scientists studied the phenomena of global warming and the resulting changes to the climate, but they've been slowly making sense of what's going on. Studies have even pointed to the effects of the Antarctic ozone hole as possibly having a role.

"Its really not surprising to people in the climate field that not every location on the face of Earth is acting as expected – it would be amazing if everything did," said Claire Parkinson, a senior scientist at NASA’s Goddard Space Flight Center, according to a NASA statement. "The Antarctic sea ice is one of those areas where things have not gone entirely as expected. So it's natural for scientists to ask, 'OK, this isn't what we expected, now how can we explain it?'"

(Source: NASA/NISDC)