A huge hole nearly the size of the state of Maine or Ireland has opened up in the thick sea ice blanketing Antarctica’s Weddell Sea.
The strange ice-free area was first spotted in the 1970s in the midst of the harsh Antarctic winter, despite frigid temperatures – and now, 40 years after it closed, the so-called Weddell Polynya has returned.
Scientists are now working to understand how often the massive hole appears, and how climate change could affect it.
A huge hole nearly the size of the state of Maine has opened up in the thick sea ice blanketing Antarctica’s Weddell Sea. The massive polynya can be seen in the map of the sea ice distribution around Antarctica above, circled in red
A ‘polynya’ is a large ice-free area that develops in an otherwise frozen sea; the features are commonly seen in both the Arctic and Antarctic sea ice.
As these ice gaps typically form in coastal regions, however, the appearance of a polynya ‘deep in the ice pack’ is an unusual occurrence, according to Motherboard.
‘It looks like you just punched a hole in the ice,’ atmospheric physicist Kent Moore, a professor at the University of Toronto Mississauga, told Motherboard.
‘This is now the second year in a row it’s opened after 40 years of not being there,’ Moore explained.
‘We’re still trying to figure out what’s going on.’
Researchers, including a group at the GEOMAR Helmholtz Center for Ocean Research Kiel, have been closely monitoring the polynya since it first reappeared in the satellite data.
Studies led by the Kiel team previously suggested the feature was a long-term natural variability – meaning it would come back sooner or later.
And now, it has.
‘For us this ice-free area is an important data point which we can use to validate our climate models,’ says Dr Torge Martin, meteorologist and climate modeller in the GEOMAR Research Division ‘Oceans Circulation and Climate Dynamics.’
‘Its occurrence after several decades also confirms our previous calculations.’
At its peak, the Weddell Polynya measured a staggering 80,000 square kilometers (roughly 31,000 square miles).
As these ice gaps typically form in coastal regions, however, the appearance of a polynya ‘deep in the ice pack’ is an unusual occurrence. The Weddell Polynya can be seen in the Southern Ocean, above
It’s larger than The Netherlands, and nearly the size of Lake Superior.
While its reappearance has spurred some questions, the experts say the processes driving it are relatively well- understood.
‘The Southern Ocean is strongly stratified,’ says Professor Dr Mojib Latif, head of the Research Division at GEOMAR.
‘A very cold but relatively fresh water layer covers a much warmer and saltier water mass, thus acting as an insulating layer.
‘This is like opening a pressure relief valve – the ocean then releases a surplus of heat to the atmosphere for several consecutive winters until the heat reservoir is exhausted.’
Simulated temperature development in the area of the polynya is illustrated above. The cold surface layer is shown in blue, with warm water indicataed in red. Years with polynyas are marked by a black bar
Still, it’s unclear how often the Weddell Polynya re-emerges, and how long it will linger now that it’s opened back up.
Experts say it’s too early to know how climate change has affected the formation of the huge polynya, if it’s to blame at all.
But, with new observations using technology far more advanced than that available when it first appeared 40 years ago, they’re hoping to uncover some answers.
‘Global warming is not a linear process and happens on top of internal variability inherent to the climate system,’ Latif says.
‘The better we understand these natural processes, the better we can identify the anthropogenic impact on the climate system.’