What Is A Polynya? Antarctica's Massive Hole, Explained
On Dec. 11, 1972, at Vandenberg Air Force Base in California, the U.S. government launched an unmanned satellite named Nimbus V, one of the first satellites sent to observe Earth from space. In 1974, researchers were treated to images of Antarctica, including the Weddell Sea, an area of open ocean between the southern continent and the Atlantic. It was there that researchers observed the sea ice that covered the water during the Antarctic winter — but there was a hole in the ice in Antarctica, as big as the state of Oregon. It reappeared the next winter, when the ice spread out over the water, in the same spot, and again in 1976. But then in 1977 it disappeared, not to be seen for 40 years. But now, the hole is back.
Researchers studying the region have found a massive hole in Antarctica the size of Maine in the Weddell Sea, and "There's a lot of pretty cool stuff going on about it," Dr. Hannah Zanowski, a post-doctoral fellow at the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) who studies Antarctic oceanography, tells Bustle.
The existence of this natural phenomenon could mean a change in some of researchers' assumptions about how the ice and the ocean interact with each other, and give researchers new data that they've never been able to get from the frozen region. "A lot of the community is quite excited," Zanowski says.
Holes in the Antarctic ice, called polynyas, are not inherently uncommon. According to Rob Sherrell, a professor at Rutgers' Department of Marine and Coastal Studies, there are about 40 "recurring polynyas that open up every summer" around Antarctica's coast. "They're a result of seasonal changes in winds, mostly," he tells Bustle. But this one, he adds, "is a bit odd."
So why is it such a big deal? This polynya is special "because it's out in the open ocean, far from shore, and it's kept open by an upwelling of warm water, which melt ice at the surface," Jaime Palter, an assistant professor of oceanography at the University of Rhode Island, says. "In this region of the ocean, there's slightly colder and fresher water on top, and then underneath the surface there's some warmer saltier water."
The warmer water (which is pretty cold, at just a few degrees above freezing) rises upward and melts the ice on the surface. Ultimately, the formation of the polynya comes down to two ocean features: the Weddell Gyre, which is a system of ocean currents, and the Maud Rise, an underwater plateau.
"Antarctic sea ice experts do not fully understand the processes that form the polynya," Zanowski adds. "But we think that a combination of the currents of the Weddell Gyre and the Maud Rise, an underwater seamount, cause it to form in the place it does." The currents of the Weddell Gyre and the underwater plateau cause the warm water to sit closer to the surface, which makes it easier for the warm water to flow upward and create a polynya.
What leaves experts really flummoxed is why the Weddell polynya disappeared for 40 years and why it's back now.
In 2014, Palter joined with other researchers on a paper in Nature Geosciences arguing that the polynya hadn't formed since the 1970s in part due to global warming, which led to fresher water on the surface that changed the water flows. With the polynya coming back, though, some of the paper's conclusions may have to be reevaluated. Palter says she is excited to test her research with real-world data. "We always wondered if we'd get another chance to see one of these events. The last one was before I was born and certainly before my student was born," she adds, referring to one of the co-authors on the paper. "So in the scientific community, everyone's super excited."
The surprise of the polynya is leaving experts reaching for all sorts of possible explanations. Cecilia Bitz, a professor in the Atmospheric Sciences department at the University of Washington, is interested in how this unexpected event could be related to another one that happened in Antarctica last year, when sea ice surrounding the continent reached its lowest level on record during the summer. The ice seemed to have mostly refrozen during the winter this year, but Bitz tells Bustle she wonders whether the rapid refreezing of the ice since its low point may have led to changes in the seawater.
"That's an extraordinary event," Bitz says, "and I'm very curious if these things are related, because why would you have something that's so extraordinary last November and December and then less than a year later, another surprise like this?"
Research on the new polynya is already underway. The Southern Ocean Carbon and Climate Observations and Modeling project (SOCCOM), a joint research project housed at Princeton that studies how climate change affects oceans near the South Pole, has sent some robotic floats to the area of the polynya to take measurements of the water affected by the hole. According to SOCCOM's press release on the polynya, one of their floats surfaced within the polynya by accident, allowing it to take readings. SOCCOM declined to comment for this article, hoping to publish its findings once the data can be fully evaluated.
The effects of the polynya could also reach far beyond Antarctica and its oceans. Cold water from the poles flows throughout the world. The water's density and coldness lead to it sinking down into abysses in oceans all the way on the other side of the globe. "While the polynya is open, the exposure of more water to the cold air during the winter could lead to the formation of more Antarctic Bottom Water, a specific mass of water that fills the deep parts of the ocean worldwide," Zanowski tells Bustle.
It probably won't have a noticeable effect in most of the world if the polynya remains this size and is only a short occurrence, but if the hole in the ice continues over the next years, it could impact ocean circulation in ways we don't yet fully understand.
Experts say that the polynya is probably not a direct result of climate change — it's not caused by warmer air temperatures, but by changes in the movement of different masses of water under the ocean. But with so many oceanic factors contributing to it, there are certainly ways that effects of climate change could have contributed to it. For people who study the Antarctic oceans and the ice that covers them during the winter, this is the kind of event that gets everyone eager to find out whatever they can.