Waves alter Antarctic polynyas by breaking up surrounding sea ice

Antarctic polynyas are puzzling areas of open water surrounded by ice. They are formed by powerful winds that push ice away, exposing the ocean to the cold. Waves are generated in these polynyas, but scientists hadn't thought much about how these waves might impact the surrounding ice. Our research, published in Nature Communications, reveals that during extreme wind events, waves inside the Vincennes Bay Polynya in East Antarctica can become strong enough to break up nearby sea ice from the inside out.

This discovery came about when we were studying how waves from the Southern Ocean travel through hundreds of kilometers of ice. During some of our deployments, our wave-measuring buoys drifted into the Vincennes Bay Polynya after the ice they were attached to broke away. Repeated observations led us to wonder if these waves could be powerful enough to fracture the surrounding ice and affect the polynya's evolution.

When waves meet sea ice, they cause it to bend, and if the stress is great enough, the ice can crack. Our analysis shows that waves generated inside the polynya can easily meet this threshold. The breakup sets off a chain of events: the fragmented ice becomes more mobile as wind and waves redistribute it. This process has been observed in satellite data, with sea-ice concentration around the polynya dropping by up to 30% following extreme wind-wave events, sometimes persisting for a week or more.

The redistributed ice also forms more actively, as satellite observations show larger areas of new sea ice forming after these events. While our findings come from one polynya during extreme conditions, the relevance of these processes to other Antarctic coastal polynyas and their potential impact remains uncertain. However, as Antarctic coastal polynyas are becoming larger, understanding how locally generated waves influence these environments is crucial.