(AP) – A giant hole almost the size of the state of Maine has opened up in Antartica’s winter sea ice cover, leaving scientists with a handful of unanswered questions.
The hole, known as a polynya, was discovered about a month ago in Antartica’s Weddell Sea as a team of scientists from the University of Toronto and the Southern Ocean Carbon and Climate Observations and Modeling project used satellite technology to monitor a similar, much smaller, hole that opened last year.
Scientists say it’s the first time a hole of this magnitude has been observed in the Weddell Sea in over 40 years. In their observations, it has fluctuated in size up to a maximum of nearly 80,000 square kilometers.
In 1974, an even bigger hole in the ice — 250,000 square kilometers — opened in the same location.
Now researchers are trying to figure out why it recurred.
“We don’t really understand why it went away for 40 years and has come back now,” Kent Moore, professor of physics at the University of Toronto, told CBS News. “It’s like an enigma on many levels.”
There are two types of polynyas: coastal and open-ocean. Coastal polynyas form right at the coast, mainly due to strong winds which blow ice out of the area.
“These coastal polynyas occur all the time. They’re always there,” Moore said. “Polynyas that form deep in the ice pack are a lot rarer. It’s a different mechanism.”
Open-ocean polynas, like the one found in the Weddell Sea last month, are caused by the rising of warmer and saltier water from below.