In the presence of climate change, sea ice levels are falling globally. This loss is mainly fueled by dramatically receding ice extents in the Arctic. Meanwhile, Antarctic sea ice is experiencing historic growth.
As Earth rolls through yet another year of record heat, the threat of melting polar glaciers is as grave as ever. However, perhaps a less often discussed topic involves sea ice. In the Arctic, sea ice continues to plummet to all-time minimums. This is not surprising. What is interesting, is that Antarctic sea ice has been reaching historic maximums. In 2014, Antarctic sea ice was observed at a higher level than any other time in documented history*.
If the global climate is warming, what is the cause of this apparent increase is sea ice in the Antarctic? The answer, it turns out, may be found as a result of the same processes that cause ice shrinkage in the Arctic.
According to meteorologist and climatologist Eric Holthaus, there are several hypotheses as to why Antarctic sea ice appears to be contradicting a warming trend seen nearly everywhere else on Earth. First of all, it’s important to understand the geographies of the Arctic and Antarctic are fundamental opposites. The North Pole is ocean surrounded by land whereas the South Pole is a continent surrounded by ocean. This results in very different reactions upon the seascape to climate change. Additionally, the Southern Ocean is actually warming, though one explanation suggests this temperature change could very well be causing the seemingly paradoxical increase in sea ice. Warmer ocean temperatures would be effective at melting land-sea glaciers along the shores of Antarctica. This process releases freshwater into the sea, thereby decreasing local ocean salinity and raising the freezing point of the water.
A second explanation contends that, through the same process of salinity-reduction, increased precipitation caused by warmer, more water vapor-rich air, in the Southern Ocean is helping the formation of sea ice. Lastly, partly due to the hole in the ozone layer, increasing speeds of winds encircling the continent may be helping to push ice further out to sea, consequentially increasing the areal extents of sea ice.
Likely, all three hypotheses combined explain the apparent Antarctic sea ice increase. However, it is not a trend that is expected to continue for much longer. Holthaus states in his article published originally in Slate:
“Eventually, scientists expect the sheer temperature increase from global warming to swamp whatever complex combination of atmospheric and oceanographic physics that’s producing the counterintuitive ice growth, and Antarctic sea ice will begin to decline as Arctic ice already has.”
The Big Deal with Sea Ice
Sea ice is very different from glacial ice. Whereas as glaciers form over land, fueled by snowfall, sea ice is comprised of frozen ocean water. Glacial loss is observed primarily in terms of volume. As glaciers melt, the corresponding sea level increase is observed as more water is introduced into the ocean. Sea ice, on the other hand, is measured in extents.
Every year, sea ice melts and re-freezes in a fairly predictable fashion. Over time, we can see changes in maximum and minimum extents. However, we are not as concerned with sea ice “melting” as we are with glacial melting. Rather, it has to do reflectivity. Ice is bright white and is very good at reflecting the Sun’s energy back into space. This is called albedo. Ocean water, on the other hand, is darkly colored, absorbing solar energy and storing heat, ultimately increasing the rate of regional and global warming.
Though Antarctic sea ice is increasing, it is not doing so at a rate nearly fast enough to overcome the extreme losses in the Arctic. The rate of decrease in the Arctic is roughly three times that of the rate of increase in the Antarctic meaning that global sea ice is still falling, and fast.
However, a reduction in sea ice also can have advantages such as increasing accessibility to shipping lanes and opportunities for resource extraction in areas otherwise obstructed by ice. No matter the advantages though, shrinking sea ice will likely present more problems worldwide than it solves as global climate change accelerates.
*Due to the nature of sea ice, detailed records only exist as far back as 1979 when satellite imagery was first able to be gathered for research purposes.