What is a Polynya?

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Polynya is an oceanography term borrowed from the Russian (полынья) to refer to an open body of water surrounded by ice. Polynyas are mostly found in the Arctic and the Southern Oceans of Antarctica.

A polynya that has formed in an embayment where the Venable Ice Shelf meets Farwell Island in Antartica.  Photo: John Sonntag/NASA, public domain.
A polynya that has formed in an embayment where the Venable Ice Shelf meets Farwell Island in Antartica. Photo: John Sonntag/NASA, public domain.

How do Polynyas Form?

Polynyas can form in two ways. Coastal polynyas form when offshore winds push sea ice away from the coastline. Coastal polynyas can also form through the warm upwelling of seawater. In this satellite image taken off the coast of Antarctica, near Ross Island and McMurdo Station on November 16, 2011, a polynya has formed. The polynya was most likely formed by katabatic winds which blow from Antartica’s high interior and can reach speeds up to 200 miles (320 kilometers) per hour.

 Polynya off the coast of Antarctica, near Ross Island.  Image: NASA, November 16, 2011.
 Polynya off the coast of Antarctica, near Ross Island. Image: NASA, November 16, 2011.

Open-ocean polynyas form when cracks form in the ice sheet far offshore, exposing the seawater. An example of a open-ocean polynya is Maud Rise polynya, located in the eastern Weddell Sea. This polynya is named after the submerged mountain-like feature over which the opening in the sea ice forms. The Maud Rise polynya can vary greatly in size, occurring routinely in early spring and sometimes over the winter. During the fall of 2017, the Maud Rise polynya grew from 9,500 square kilometers in mid-September to 80,000 square kilometers by late October.


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NASA’s Terra satellite captured the Maud Rise Polynya on September 25, 2017:

Maud Rise polynya.  Image: NASA, September 25, 2017.
Maud Rise polynya. Image: NASA, September 25, 2017.

References

Deciphering the Maud Rise Polynya. (2019, May 22). Retrieved from https://earthobservatory.nasa.gov/images/145069/deciphering-the-maud-rise-polynya

Polynya off the Antarctic Coast. (2011, November 22). Retrieved from https://earthobservatory.nasa.gov/images/76474/polynya-off-the-antarctic-coast

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