It appeared in 1973, seemingly out of nowhere: a hole in the sea ice off the coast of Antarctica. But this was no ordinary hole. It was gigantic – almost half a million square kilometers.
The mysterious doorway remained in place for the next three winters. It then largely disappeared before re-emerging in 2017 with a giant mouth of 80,000 square kilometers.
This giant hole – the so-called polynya – is an area of open water surrounded by sea ice, something like the opposite of an iceberg.
The mysterious Weddell Polynya, which emerges over the Maud Reese oceanic plateau, in the Weddell Sea in the Southern Ocean, is a fairly striking example of this ecological phenomenon. Why it appears so quickly and at the same time so rarely has long puzzled scientists.
Last year, researchers suggested that for the Weddell polynya to emerge so quickly, a number of climatic anomalies must coincide at the same time.
September 25, 2017. NASA.
Another 2019 study by scientist Diana Francis showed what constitutes one such anomaly: scars from severe cyclones caused by atmospheric circulation that can pull sea ice in opposite directions and away from the center of a storm, creating a giant hole.
Francis, now a senior research fellow at Khalifa University, UAE, has just done new research that sheds light on another related phenomenon that has been largely overlooked: atmospheric currents of warm, humid air.
In the new study, Francis and her team analyzed atmospheric data dating back to the 1970s and found that these 'streams in the sky' played a 'decisive role' in the formation of the Weddell polynya in 1973 and 2017.
“I was surprised to see the almost instantaneous melting of sea ice, beneath atmospheric currents, during the coldest months of the year in Antarctica,” Francis told Nature Middle East.
The researchers say atmospheric circulation transported a strip of warm, humid air from the coast of South America to the polar region, causing melting through a combination of effects including: heat release in the air mass; local greenhouse effect generated by water vapor; and contribution to cyclone dynamics.
'Atmospheric currents also intensify storms because they produce more water vapor. They are connected, not independent, 'explained Frances.
Given that both atmospheric currents and cyclones are predicted to intensify with global warming, this strange discovery off the coast of Antarctica is more common.
The results are published in Science Advances.
Sources: Photo: NASA
