The steady and dramatic Arctic sea ice that has been recorded in the last three decades has become a topic of great interest to the media and people in general, as it can be seen as a clear sign of global warming. However, the other side of the world, something more complex is going on, to the point of generating an apparent contradiction that seems to give them reason to climate change skeptics.
A new study, conducted by the team of climatologist Claire Parkinson, of Goddard Space Flight Center of NASA, Greenbelt, Maryland, shows that from 1978 to 2010, the total area of sea ice around Antarctica grew to approximately 6,600 square miles each year on average. Considering the results of a previous study by the same authors, this growth rate has accelerated recently, as the average between 1978 and 2006 was less than 4,300 square miles per year.
However, this enigmatic phenomenon which seems to contradict the perceived reality of global warming, has an explanation.
Earth’s poles have very different geographies. The Arctic Ocean is surrounded by North America, Greenland and Eurasia. These large masses catch most sea ice annual cycle of freezing and thawing. But a large fraction of the oldest Arctic ice is gone and thicker over the past three decades. The summer ice cover is shrinking and left exposed to direct sunlight into the dark ocean water, which absorbs more sunlight than ice, which causes it to heat up even more and cause further contribute to ice losses.
At the opposite end of the planet, Antarctica is a continent surrounded by open sea, allowing the sea ice expands in the winter, but also offers less protection from the sun during the melting season. Nevertheless, the total extent of sea ice surrounding Antarctica has tended to increase in recent years, as mentioned.
Parkinson and Don Cavalieri, of the NASA center believe that this pattern contrasted ice cycle could be due to changes in atmospheric circulation. Recent studies point to the weakening of the ozone layer over the South Pole as a possible cause. Ozone retains solar energy that would otherwise be lost. Because of this, the lowest concentration over Antarctica can cause a cooling of the stratosphere (the layer of the atmosphere which is at an altitude of between 10 and 50 kilometers (6 to 30 miles). Meanwhile, the temperate latitudes have been warming, and the temperature gradient has strengthened circumpolar winds that blow over the Ross Ice Sheet.
So, those winds acting on the Ross Ice Sheet are growing stronger, and that causes the sea ice is pushed offshore, causing the appearance of sea areas near the coast and devoid of ice. The larger coastal areas devoid of ice, new ice will be generated, because in these areas the water is in direct contact with the cold winter atmosphere and freezes quickly. Therefore, as explained Josefino Comiso of NASA’s Goddard Space Flight, as the wind keeps blowing, the northernmost ice can be extended.
However, it is important to understand that in the Arctic Sea ice is lost much of the gains in the Southern Ocean. The extent of the ice cover of the Arctic Ocean in September 2012 was 1.32 million square miles less than the average extent from 1979 to September 2000. The area of ice lost roughly equivalent to that occupied by two Alaskas.
As Parkinson underlines the fact that some areas of the Southern Ocean are cooling and producing more sea ice does not prove that global warming is a false perception. “The weather does not change uniformly. Earth is very large and the expectations are certainly different changes are recorded in different regions of the world,” said Parkinson.