The first satellite images of Antarctica taken during the mid-1970s exposed a huge ice free region within the ice pack of the Weddell Sea. These ice free regions known as Polynya closed after three years. Researchers believed that it was the presence warm water in the region that prevented the formation of the ice.
It has been over 40 years and the huge polynya, the size of New Zealand, has not reappeared. The scientists declared it as a rare natural occurrence.
However, the new study led by researchers at McGill University claims that the Weddell poylnya of the 1970s may have been the last event, of what was earlier a common feature of southern Ocean, and is currently suppressed due to the effects of the accelerating climate change on the salinity of the ocean.