Polynyas are areas of open water that persist where sea ice should form, often due to upwellings of warm ocean water, or to prevailing winds.
This natural-color image from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite shows a polynya off the Antarctic coast near Ross Island and McMurdo Station on Nov. 16.
The water feature probably arose due to katabatic winds, blowing onto the ocean from the Antarctic high interior at speeds of up to 200 miles (320 kilometers) per hour.
In the photo, sea ice has been pushed away non-uniformly by strong winds that are partially blocked by Ross Island and mountains to the west, allowing more ice to remain near these landmarks.
Variations in sea ice thickness to the north of the polyna may be due to a mixture of windy and quiet weather periods.
NASA’s IceBridge mission has been investigating polynas along with sea ice and ice shelves, using plane radar and lidar to generate a three-dimensional overview of ice at the South Pole.
