A new discovery by scientists at McGill University suggests that heat from the depths of the ocean is being trapped under the Antarctic ice shelf -- all the result of climate change.

In the 1970s, researchers in Antarctica observed an open body of water the size of New Zealand within an ice pack in the Southern Ocean's Weddell Sea.

Until now, they believed the phenomenon, known as the Weddell polynya, to be a rare occurrence. But researchers at McGill say that the polynya in Antarctica has been effectively held shut for nearly 40 years because of global warming.

“The fact that we can still have a surprise like this after studying the climate system for decades shows just how complex and dangerous (climate change) is,” study co-author Eric Galbraith told CTVNews.ca.

According to the research, increased precipitation in the Southern Ocean and the melting of glaciers on Antarctica as a result of climate change has flooded the ocean with massive amounts of freshwater, preventing the warm water underneath from rising to the top.

The deep ocean is like the “basement of the climate system” and without polynya, “there’s a trapped door to the basement,” Galbraith said.

Working alongside researchers from the University of Pennsylvania, McGill researchers analyzed measurements conducted over a 60-year period by ships and robotic floats in the ocean around Antarctica.

Their study, published on Mar. 2 in the journal Nature Climate Change, shows that the deep ocean heat, trapped under a freshwater lid, has been unable to escape and melt the Antarctic ice pack that forms in the winter.

“Deep ocean waters only mix directly to the surface in a few small regions of the global ocean,” lead author Casimir de Lavergne said in a statement. “So this has effectively shut one of the main conduits for deep ocean heat to escape.”

While Galbraith says there hasn’t been any immediate impact on marine life, having a “trapped door” cuts off the oxygen supply to species in the deep ocean.

“Just like fish in a fish tank that rely on an aerator, deep sea fish need oxygen to be supplied from the air above,” he said. “It will take many decades for the oxygen to get used up, but eventually it will make it hard for the deep sea fish to breathe.”

Galbraith says it’s unlikely the polynya will ever reappear, but if it does, nearly 40-years’ worth of heat and carbon dioxide will be released from the depths of the ocean.