instrument on the
Aqua (satellite) satellite, September 25, 2017 The size of New Zealand, it re-occurred each winter between 1974 and 1976. These were the first three austral winters observed by the
Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR). From 1976 to 2015, this polynya was rarely observed. The polynya reoccurred in 2016, and has since appeared in 2017. The 2010s occurrence has been smaller than the 1970s occurrence, being about the size of Maine in 2017, or roughly . Since the 1970s, the polar Southern Ocean south of the
Antarctic Circumpolar Current has freshened and stratified, likely a result of anthropogenic
climate change. Such stratification may be responsible for suppressing the return of the Weddell Sea polynya. More recently, it was found that intense cyclones occurring over the ice pack, far south from the ice edge, were at the origin of the reoccurrence of the Weddell or Maud Rise Polynya in austral winter 2017. In certain winter months, the general atmospheric circulation around Antarctica exhibits a strong zonal wave 3 pattern, which favors the development of polar cyclones closer to the coast, that is, over preconditioned oceanographic areas for polynya formation, such as the Weddell Polynya in the
Lazarev Sea and the Cosmonaut polynya in the
Cosmonaut Sea around Antarctica. ==Other Antarctic polynyas==