In the early 1970s, when satellites first began snapping photos of Earth, scientists noticed a mysterious hole in one of Antarctica’s seasonal ice packs, floating on the Lazarev Sea. Come summertime the gap had disappeared, and for decades the strange event went unexplained.
Then, a year and a half ago, during the continent’s coldest winter months, when ice should be at its thickest, a giant 9,500-square-kilometre hole (almost 3,700 square miles) suddenly showed up in the same ice pack. Two months later it had grown a stunning 740 percent larger, before once again retreating with the summer ice.
It’s taken decades, but scientists think they finally understand why this keeps happening. Using satellite observations and reanalysis data, researchers from New York University Abu Dhabi (NYUAD) have found that these ephemeral holes, known as polynyas, appear to be scars from cyclonic storms.
In September of 2017, as warm air and cold air collided at the South Pole, the authors explain that the swirling inward winds of a cyclone – reaching 117 kilometres an hour (72 mph) and whipping up waves 16 metres high (52 feet) – pushed the Antarctic ice pack in all directions and away from the eye of the storm, like a drill to the water below.
As dramatic as it appears in satellite imagery, the resulting polynya isn’t necessarily bad. In fact, these icy punctures can be downright important. As a door between the ocean and the sky, they offer crucial pathways for wildlife, including seals and penguins, and provide habitat for phytoplankton.
These gaps are also powerful influencers of the atmosphere and a potential indicator of climate change.
“Once opened, the polynya works like a window through the sea-ice, transferring huge amounts of energy during winter between the ocean and the atmosphere,” says lead author of the new research, NYUAD atmospheric scientist Diana Francis.
“Because of their large size, mid-sea polynyas are capable of impacting the climate regionally and globally as they modify the oceanic circulation.”
It is this point that is particularly important. Because while polynyas aren’t necessarily disastrous, from what we know their presence can absolutely have an effect on the climate, something that scientists are cautious about given the current state of global warming.
Even if they don’t stir up more climactic changes or feedback systems, an abundance of these holes could throw our climate models right out of whack.
“Given their large size in the middle of the ice pack, mid-sea polynyas, through intense deep convection, are capable of impacting the climate locally, regionally, and potentially globally by modifying the oceanic circulation underneath,” the authors write in their paper.
“This includes impact on the regional atmospheric circulation, the global overturning circulation, Antarctic deep and bottom water properties, and oceanic carbon uptake.”
The range of factors that these holes could suddenly influence is astonishing, and the risk of them occurring more often is high. Under warmer climates, previous research indicates that cyclone activity at Earth’s poles will only intensify, and extratropical cyclones (aka mid-latitude cyclones) will move closer and closer to Antarctica.
“Given the link between polynya and cyclones we demonstrated in this study,” says Francis, “it is speculated that polynya events may become more frequent under warmer climate because these areas will be more exposed to more intense cyclones.”
When it comes to the climate crisis, another atmospheric variable is about the last thing we need.
This study has been published in Journal of Geophysical Research: Atmospheres.