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Instruments attached to seals collect data on conditions under the sea ice. (University of California Santa Cruz Photo / Dan Costa)

For years, giant holes in Antarctic sea ice have confounded scientists. But this week researchers from the University of Washington announced a breakthrough.

The mysterious phenomenon: Giant holes in the winter ice on Antarctica’s Weddell Sea sometimes form without explanation. In 2016 and 2017, two of these “polynyas” appeared. The second one was roughly the size of the Dominican Republic. Polynyas act as temporary habitats for Antarctic animals like penguins and seals.

What they learned: A new study led by the University of Washington and published in the journal “Nature” this week revealed a number of converging factors cause a polynya to form. Researchers found that hurricane-force winds surrounding Antarctica can cause sea ice on the surface to plunge down and warmer water from the depths to shoot upward. That water chills as it rises, making it denser than the water below. It sinks back down creating a cycle that results in a massive hole of liquid water at the surface despite temperatures far below freezing.

“Essentially it’s a flipping over of the entire ocean,” said UW oceanographer Earle Wilson, a co-author of the study.

The tech that made it possible: The oceanographers behind the study relied on the Southern Ocean Carbon and Climate Observations and Modeling project, which uses instruments drifting on currents to monitor conditions. They also collected data from the Argo ocean observing program in which robotic devices attached to elephant seals beam back data and images.

UW researchers Ethan Campbell (right) and Stephen Riser (second from left) with one of the instruments built at the UW to monitor conditions in the Southern Ocean. (UW photo / Dennis Wise)

A surprising twist: Scientists theorized that polynyas would become less frequent under climate change because the fresh water melting from glaciers makes the Southern Ocean’s surface layer less dense. This study contradicts that theory and suggests that the increasingly strong winds drawing closer the coast of Antarctica will actually cause more polynyas to form.

What it means for the planet: Increased polynyas could have consequences for major ocean currents because they circulate some of the deepest seawater. The deep contains carbon from life that could be released into the atmosphere when it reaches the surface, according to UW.

“A large carbon outgassing event could really whack the climate system if it happened multiple years in a row,” said Ethan Campbell, lead author of the study.

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