A mysterious hole nearly the size of South Carolina has opened in Antarctica's ice

A massive hole opened in the middle of the frozen Weddell Sea of Antarctica last month.

Persistent areas of open water in places where you'd expect sea ice, such as in the Arctic and Antarctic, are known as polynyas, according to the National Snow and Ice Data Center.

This Weddell polynya, however, is somewhat remarkable.

No one knows why it formed, and the hole is located quite far from the sea ice coastline, where such openings more frequently appear. And despite being exposed to freezing wintry winds over the past month, the polynya has persisted — so whatever force caused it to form is strong enough to keep it from refreezing.

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Weddell seal and pup swimming underwater in Antarctica.

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A cable portrudes from the ice wall at Explorers Cover, New Harbor, McMurdo Sound, Antarctica. The cable is used for the Remotely Operable Micro-Environmental Observatory (ROMEO), an underwater camera. Connected to onshore equipment and linked by radio to

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The Marbled Rockcod (Notothenia rossii) copes with the icy waters of Antarctica by means of a biological antifreeze in its body fluids, Antarctica.

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Antarctic krill (Euphausia superba), key species in the Antarctic ecosystem. Grows to 6 cm and occurs in densities ranging up to 30,000 in a cubic metre. 

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Unidentified large jellyfish in brash ice, Cierva Cove, Antarctica, Southern Ocean, Polar Regions.

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Icefish in Antarctica have no scales or haemoglobin, so their blood is white.

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Antarctic Sea star (Odontaster validus) in Antarctica.

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Antarctic Sea urchin, (Sterechinus neumayeri) with camouflage attached, Antarctica.

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Antarctic Limpet (Nacella concinna) in Antarctica.

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Barbed plunder fish in Antarctic underwater.

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Antarctica, Cuverville Island, Underwater view of Comb Jellyfish swimming beneath ice along plankton-filled shallow water.

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Orange yellow anemone surrounded by brown algae, Antarctica.

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Two yellow sea stars and white worm strands, Antarctica.

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But it's not the first time this particular hole has appeared. Scientists observed a similar polynya in the same area of Antarctica in 1974, according to NASA Earth Observatory. It reappeared during the austral winters of 1975 and 1976, then disappeared and it didn't re-emerge for decades. It re-appeared again in August 2016, though significantly smaller than it had been in the 1970s.

Now it's back and bigger than last year. The largest estimates of the hole's current size put it around 80,000 square kilometers or just over 30,000 square miles — almost as big as South Carolina. That's still far smaller than the 1970s version, which reached 300,000 square kilometers, about the size of Arizona.

It's easy to assume that a massive hole in sea ice is related to climate change, but that may not be the case. Some scientists speculate that the formation of the Weddell polynya is part of a cyclical process, though the details are unclear.

"Why was the Weddell polynya present in the 1970s, and then absent until its recent reappearance?" Willy Weeks, a retired sea ice geophysicist from University of Alaska in Fairbanks told NASA Earth Observatory when the hole first re-emerged in 2016. "Did the Weddell polynya occur before 1970, and we are looking at a periodic process that shows itself about every 40 years? If there were earlier occurrences, there is no record of them."

SOCCOM 

Polynyas allow heat to escape the ocean, cooling the top layer of water. As that water becomes colder and denser, it sinks, allowing more warm water to rise and keep the hole open. That sinking water contributes to the cold water mass known as Antarctic Bottom Water, according to NASA, which feeds into deep ocean currents and contributes to ocean circulation around the globe.

It's possible that the phenomenon is a key part of the process that supplies Antarctic Bottom Water, according to Earther's in-depth look at the polynya.

Part of the reason this polynya remains so mysterious is that it's hard to explore sites like this. Winter air temperatures there are thought to be about negative 20 degrees Celsius and there are few flights or expeditions in Antarctica during the winter months.

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ANTARCTICA - OCTOBER 31: A section of ice near the coast of West Antarctica is viewed from a window of a NASA Operation IceBridge airplane on October 31, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 31: IceBridge Project Scientist Nathan Kurtz looks out over ice near the coast of West Antarctica from a window of a NASA Operation IceBridge airplane on October 31, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of up to 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 31: A section of the West Antarctic Ice Sheet with mountains is viewed from a window of a NASA Operation IceBridge airplane on October 31, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 31: A section of the West Antarctic Ice Sheet is viewed from a window of a NASA Operation IceBridge airplane with the airplane shadow visible on October 31, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Ice crevasses are viewed near the coast of West Antarctica from a window of a NASA Operation IceBridge airplane on October 28, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Ice floats near the coast of West Antarctica as viewed from a window of a NASA Operation IceBridge airplane on October 28, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Tabular icebergs float near the coast of West Antarctica as seen from a window of a NASA Operation IceBridge airplane on October 28, 2016 in-flight Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Sea ice streaks are viewed near the coast of West Antarctica from a window of a NASA Operation IceBridge airplane on October 28, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Sea ice floats near the coast of West Antarctica from a window of a NASA Operation IceBridge airplane on October 28, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Ice is viewed near the coast of West Antarctica from a window of a NASA Operation IceBridge airplane on October 28, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA- OCTOBER 28: NASA flight suits hang inside a NASA Operation IceBridge DC-8 research airplane on October 28, 2016 flying near the coast of Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Mission scientist John Sonntag works inside a NASA Operation IceBridge DC-8 research airplane on October 28, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 28: Ice is viewed near the coast of West Antarctica from a window of a NASA Operation IceBridge airplane on October 28, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA - OCTOBER 27: Ice floats in West Antarctica as seen from a window of a NASA Operation IceBridge airplane on October 27, 2016 in-flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
ANTARCTICA- OCTOBER 27: Ice floats near the coast of West Antarctica as viewed from a window of a NASA Operation IceBridge airplane on October 27, 2016 in flight over Antarctica. NASA's Operation IceBridge has been studying how polar ice has evolved over the past eight years and is currently flying a set of 12-hour research flights over West Antarctica at the start of the melt season. Researchers have used the IceBridge data to observe that the West Antarctic Ice Sheet may be in a state of irreversible decline directly contributing to rising sea levels. NASA and University of California, Irvine (UCI) researchers have recently detected the speediest ongoing Western Antarctica glacial retreat rates ever observed. The United Nations climate change talks begin November 7 in the Moroccan city of Marrakech. (Photo by Mario Tama/Getty Images)
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But scientists might now have a better shot at figuring out what's happening, thanks to a key new source of data from a National Science Foundation-sponsored group studying climate in the Southern Ocean. A robotic float that was meant to be sending data from the Weddell Sea surprisingly surfaced inside the polynya last month, according to a news release from the Southern Ocean Carbon and Climate Observations and Modeling project at Princeton.

That robot began sending data that's now being processed, after which the group may be able to report new findings.

The information could help reveal answers about what triggers the formation of these mysterious holes.

NOW WATCH: Antarctica just lost another huge chunk of ice 4X the size of Manhattan — and that could be just the beginning

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