(Inside Science) -- By analyzing data from seaborne robots and sensors glued onto seals, researchers may now understand the mysterious origins of giant holes that can open up in Antarctic sea ice, a new study finds.
The biggest known polynyas in the winter sea ice of Antarctica's Weddell Sea appeared soon after the first satellites were launched, with an area the size of New Zealand remaining ice-free through three consecutive winters from 1974 to 1976, despite air temperatures far below freezing.
Scientists examined decades of satellite images of sea ice cover and data from Antarctic weather stations, and gathered data from robots drifting in Southern Ocean currents and even sensors epoxied onto elephant seals.
Intense storms that swirled over the Weddell Sea with almost hurricane-force winds those years churned relatively warm water from the deep ocean upward, melting ice and opening up polynyas in the sea ice.
Under climate change, freshwater from melting Antarctic ice sheets would make the Southern Ocean's surface waters less dense, which might lead to fewer polynyas in the future.