At the moment scientists cannot explain the origin of this hole.
After closing back up, and remaining that way for roughly 40 years, it has re-opened.
Some scientists speculate that the formation of the Weddell polynya is part of a cyclical process, though the details are unclear.
The vast hole opened up several hundred kilometres across the area of about 80,000 square kilometres - but this feature remains a mystery to researchers. At its peak, the Weddell Polynya measured 31,000 square miles, which is larger than the Netherlands and almost the size of the state of Maine.
The holes form in coastal regions of Antarctica, but what's unusal here is that this polynya is "deep in the ice pack", Moore says.
Kent Moore, a professor of physics at the University of Toronto, said: "In the depths of winter, for more than a month, we've had this area of open water".
The professor said: "This is now the second year in a row it's opened after 40 years of not being there".
'We're still trying to figure out what's going on'.
"The fact that now a large, ice-free area can be observed in the Weddell Sea confirms our theory and gives us another data point for further model studies", said Dr. Torge Martin, meteorologist and climate modeler at GEOMAR.
Scientists weren't expecting the polynya to re-appear, and aren't sure why it has resurfaced twice in the past two years.
It's larger than The Netherlands, and almost the size of Lake Superior. According to Moore, the hole is a result of other processes that aren't understood yet. Dr. Mojib Latif, head of the Research Division at GEOMAR, told the site.
'A very cold but relatively fresh water layer covers a much warmer and saltier water mass, thus acting as an insulating layer.
Simulated temperature development in the area of the polynya is illustrated above. Ocean currents bring the warmer water upwards, where it melts the blankets of ice that had formed on the ocean's surface.
A larger version of the hole was observed in satellite observations in the same area of Antarctica in 1974, and it reopened past year for a few weeks.
But researchers caution that it would be "premature" to blame it on climate change. A more thorough and prolonged research would reveal the real reason behind the huge hole.
"Global warming is not a linear process and happens on top of internal variability inherent to the climate system".