Antarctica: A vast hole that mysteriously opened in Antarctica’s sea ice in 2017, comparable in size to Switzerland has finally been explained by scientists.
The phenomenon, known as a polynya, emerged far from the Antarctic coast over Maud Rise, a 4,600-foot-tall underwater mountain.
The last time such a feature appeared in this area was in the 1970s, shortly after satellites began monitoring the polar regions. While it was once thought these polynyas might form annually, they vanished for decades until a surprise reappearance in 2017.
“2017 was the first time we’ve seen such a large and long-lasting polynya in the Weddell Sea since the 1970s,” said Aditya Narayanan, lead author from the University of Southampton.
Scientists initially attributed the hole’s formation to upwelling– when warm, salty water from deep in the ocean is brought closer to the surface, melting the ice from below. This process was driven by a faster spin in the Weddell Gyre, a powerful clockwise ocean current in the region.
However, the researchers discovered that upwelling alone couldn’t sustain the polynya. Several other forces were at work.
Extratropical storms played a significant role by moving sea ice away from Maud Rise, allowing more ocean to be exposed. At the same time, these storms pushed saltier water into the region. From above, atmospheric rivers-narrow corridors of warm, moist air added extra heat to the surface ice.
A final contributor was Ekman transport, a process where wind, influenced by Earth’s rotation, drives surface water movement. This effect brought salt-laden water directly over Maud Rise, further weakening the ice.
The study shows that it took a rare combination of oceanic and atmospheric events to open the polynya.
By September 2017, the hole froze over again, but the event offered scientists a rare opportunity to understand how delicate and dynamic Antarctica’s ice systems can be.
Researchers say understanding these processes is crucial as climate variability continues to reshape polar environments in unpredictable ways.
