According to NASA satellites, Antarctic sea ice has reached its greatest extent since the agency began keeping records in the 1970s. In what may prove to be a futile gesture, NASA has dispatched its scientists to explain why this record-breaking event does not disprove global warming.
“The planet as a whole is doing what was expected in terms of warming,” says Claire Parkinson, a senior scientist at NASA’s Goddard Space Flight Center. “Sea ice as a whole is decreasing as expected, but just like with global warming, not every location with sea ice will have a downward trend in ice extent.”
The most prominent example of this is in the Arctic. The region has lost an average of 20,800 square miles of ice every year since the late 1970s. Antarctica, by comparison, has gained an average of 7,300 square miles of sea ice. These figures reveal that the magnitude of Antarctica’s growth is approximately one-third of the Arctic’s loss.
The exact reason for the dichotomy is not known, but scientists have several theories. One of the more prominent theories is that the glacial melting taking place on Antarctica’s surface is sending more cold water into the sea and causing more ice to form. This could be due to a layering effect in the Southern Ocean, which, according to the Arc Center, could ultimately lead to a rapid acceleration in sea level rise.
The most important thing to remember, however, is that the Arctic and Antarctic are fundamentally different regions. According to NASA’s Joey Comiso, a sea ice scientist and the lead author of the cryosphere observations chapter in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change,
“Geographically, the Arctic is very different from the Antarctic. In the Antarctic, the sea ice surrounds a continent. In the Arctic, the sea ice is surrounded by land. The environmental forcings are very different and therefore the trends in the two regions are not expected to be the same or even similar.”
Atmosphere, he says, is “a major driving force.” In addition to declines in sea surface temperatures, changes in pressure and winds can accelerate ice production.
Today, Antarctica’s sea ice is massive. In the next decade or two, however, the satellite images may look very different:
“Eventually you’d expect that the Antarctic region would be affected by the long-term effects of greenhouse warming. As the region gets warmer and the ocean heat content increases in the region, we expect that ice extent will start to decline and the trend will reverse and become negative. And maybe in a bigger way, because the most extensive sea ice cover in the world is in the Antarctic region, and the ice cover is generally thinner and easier to melt completely.”