"This is hundreds of kilometers from the ice edge", he added.
Since the hole continually exposes the water to the atmosphere above, it is hard for new ice layers to form. "Its recurrence supports our hypothesis... that the Weddell Polynya was not a one-time event but possibly occurred regularly in the past".
A "polynya" is a large ice-free area that develops in an otherwise frozen sea, and this particular formation is situated in the Weddell Sea, east of the Antarctic Peninsula.
The polynyas are an area of open water in an ice-covered pond, on all sides it is surrounded by ice.
"This is now the second year in a row it's opened after 40 years of not being there", Moore told Motherboard. According to satellite imagery, it appeared in the same place as it did forty years ago. Because there is a 40-year span between the last time this happened, there's no clear pattern for scientists to follow.
The going theory, Moore said, is that ocean currents are lifting warmer waters from the ocean's depths up to the surface, where it's melting the ice. This nearly twice the size of the Netherlands and marginally smaller than Ireland. "In some cases, the high-density surface water mixes with other masses and sinks all the way to the ocean bottom", the National Snow and Ice Data Center (NSIDC) explained. Back then, the opening was as large as Oregon.
"We expect to see changes in the ocean, but it may take several years to see exactly how large those changes are and what impact they would have".
One of the biggest reason as to why this polynya remains so mysterious is that it's quite hard to explore such areas.
Known as the Weddell Polynya, it first opened and closed in the 1970s, then mysteriously reopened again last month. The cold surface layer is shown in blue, with warm water indicataed in red.
Blaming climate change for this giant hole is one alternative that the scientists have but according to Moore, that would be a premature thing. "The better we understand these natural processes, the better we can identify the anthropogenic impact on the climate system", Latif said.