A hole the size of Maine has formed in the ice in Antarctica’s Weddell Sea, and scientists have no concrete theory as to why.
This patch of water among miles of ice appeared about a few months ago during a time when the ice is normally very thick, and because of its remote location, researchers are mostly relying on satellite imagery to study it.
The going theory on what caused it has to do with water currents and a flow of warmer water rising up and melting the ice.
“The Southern Ocean is strongly stratified. A very cold but relatively fresh water layer covers a much warmer and saltier water mass, thus acting as an insulating layer,” said Mojib Latif, head of the Research Division at Geomar Helmholtz Centre for Ocean Research Kiel.
Under certain circumstances, that warmer water can break through the insulating cooler water and melt the ice—a phenomena that happens regularly around coastal areas in both the Arctic and Antarctic, but normally not in the middle of the sea.
“This is like opening a pressure relief valve—the ocean then releases a surplus of heat to the atmosphere for several consecutive winters until the heat reservoir is exhausted,” Latif added.
The warm water cools when it reaches the air, then sinks to the bottom and reheats.
This cycle could repeat for the rest of the winter, Kent Moore, a professor of physics at the University of Toronto told CBC’s “As It Happens.”
This is the second time in two years the opening in the ice—called a polynya—has appeared. The last time it happened was in 2016.
This year’s polynya is much bigger than last year’s, but is still much smaller than in the 1970s, when it appeared for three consecutive winters. The ones that formed 40 years ago were about five times bigger, said Torge Martin, a meteorologist and climate modeler at the Helmholtz Centre for Ocean Research in Kiel, Germany.
Many climate scientists thought that, based on their theories of climate change, the formation of this deep-sea polynya would not form again in the Antarctic. Because there is a 40-year span between the last time this happened, there’s no clear pattern for scientists to follow.
“Two of these events happening two years in a row really isn’t a long enough kind of trend for us to say it’s the result of global warming,” Moore told CBC.