Scientists Finally Solve the Mystery Behind South Carolina-Sized Hole That Shows Up Once in a While on Antarctic Ice

At a depth of about 0.62 miles in Antarctica’s Southern Ocean, lurks an unusual hole the size of Switzerland and South Carolina. The fugitive hole sporadically opens and closes. Since scientists first spotted it in 1974, they have been studying it to detect a pattern. When they were about to close the chapter, the hole suddenly burst open again between 1975 and 1976, exposing the dark icy waters below. Scientists were puzzled and before they could comprehend anything, the hole disappeared under the ice pack, only to reappear between 2016 and 2017. This time a team of determined researchers employed advanced technology and even recruited some seals to solve this 50-year-old mystery. They published their findings in the journal Science Advances.

The 15,444-square-mile hole appears near Maud Rise, an underwater mountain or seamount in the Antarctic Weddell Sea. Holes like these are often called “polynyas.” A polynya is a rare pocket of open water surrounded by crusted sea ice. They are often used by marine mammals like seals, whales, and penguins as breathing holes. The “Maud Rise polynya” was studied by a collective team of researchers from the University of Southampton, the University of Gothenburg, and the University of California, San Diego. They employed computer modeling and satellite imagery to investigate the hole. Several Antarctic seals were also recruited for the water-testing job. These seals were made to wear tiny helmets on their bulbous heads, plus tracker sensors were attached to their bodies.

The team was curious to understand what were the conditions that led to the opening of this mysterious hole as well as its odd timing. They concluded that the cause was “complex interactions between the wind, ocean currents, and the unique geography of the ocean floor, transporting heat and salt towards the surface,” as researchers described in a press release. In scientific terms, this phenomenon is called as “Ekman spiral.” “Ekman transport was the essential missing ingredient that was necessary to increase the balance of salt and sustain the mixing of salt and heat towards the surface water,” oceanographer Alberto Naveira Garabato of the University of Southampton, said in a statement.

"This upwelling helps to explain how the sea ice might melt. But as sea ice melts, this leads to a freshening of the surface water, which should in turn put a stop to the mixing," Fabien Roquet, a physical oceanography professor at the University of Gothenburg in Sweden, said in the same statement. "So, another process must be happening for the polynya to persist. There must be an additional input of salt from somewhere." Salt can significantly lower the freezing point of water, according to Science Alert. So, it’s Weddell’s saline water that’s helping the hole remain persistent in its opening and closing dance. The turbulent eddies of Weddell’s waters push the salt to the top of the Maud Rise seamount, preventing the water in the hole from freezing.

The intriguing open-and-shut dance of this polynya will help scientists predict various climatic conditions that may manifest soon. "The imprint of polynyas can remain in the water for multiple years after they've formed," said climatologist Sarah Gille of the University of California, "They can change how water moves around and how currents carry heat towards the continent. The dense waters that form here can spread across the global ocean." While the gaping hole is shut close right now, if it shows any signs of opening again, scientists will be able to detect it four months before its opening time. So while the Antarctic seals dig cracks and breathing holes in the thickset Antarctic ice, this cavernous hole sleeps still, waiting for the eddies to trigger open its frozen latch and unleash the torrid waters.