Known by the Russian word polynya, the area surrounded by solid sea ice is hundreds of kilometers from the ice edge and researchers based at Princeton University were able to identify it thanks to satellite images. In an otherwise thick layer of sea ice, still frozen from the Antarctic winter, the hole is an aberration. "Its recurrence supports our hypothesis... that the Weddell Polynya was not a one-time event but possibly occurred regularly in the past".
Some scientists speculate that the formation of the Weddell polynya is part of a cyclical process, though the details are unclear.
A "polynya" is a large ice-free area that develops in an otherwise frozen sea; the features are commonly seen in both the Arctic and Antarctic sea ice.
Forty years after the first observation of the polynia in the sea, the Weddell did not open, and now it is the second year in a row that has opened.
The going theory, Moore said, is that ocean currents are lifting warmer waters from the ocean's depths up to the surface, where it's melting the ice. The team is making use of observations from deep sea robots and satellites and feels that the data they have now compared to 40 years ago is "amazing". This nearly twice the size of the Netherlands and marginally smaller than Ireland. As that water becomes colder and denser, it sinks and thus allows more warm water to rise above and keep the hole open. However, it disappeared for several decades before showing back up, throwing a huge kink in many scientific explanations for its existence. "On-site measurements in the Southern Ocean still require enormous efforts, so they are quite limited".
Simulated temperature development in the area of the polynya is illustrated above.
Still, it's unclear how often the Weddell Polynya re-emerges, and how long it will linger now that it's opened back up.
"We don't really understand the long-term impacts this polynya will have", he says.