Nares St. Polynya
We’ve been impressed by the size and persistence of an area of open water and unconsolidated sea ice between Greenland and Ellesmere Island, Arctic Canada. This phenomenon goes by the Russian term polynya.
NASA satellite view of the Nares St. polynya. Image ground resolution is 250 m. Blue and green reflectance is resampled from 500 m resolution data to the 250 m resolution red image. Click for a medium or full resolution version of the above graphic.
Polynyi (plural) are formed by a combination of wind action and ocean heat not allowing sea ice to form thick enough to bridge between land masses as land fast ice. More rare are polynyi formed only by wind or only by ocean heat. Prevailing winds in Nares St. above are southward, like in the below graphic from , the lower atmosphere channeled between 1000-2000 m terrain on either side of the channel.
Meteorological model output from Roger M. Samelson, Professor of Oceanic & Atmospheric Sciences
College of Oceanic & Atmospheric Sciences Oregon State University
The usual location of the Nares St. polynya is Smith Sound ~400 km south of this winter 2008/2009 position. Click for a location map with place names. The Smith Sound polynya is commonly referred to at the “North Water” polynya.
Polynyi (plural) can be associated with a tremendous heat loss from the ocean surface to the atmosphere. The sea surface is 20-40 degrees C (55-75 degrees F) warmer than the overlying air. Plumes of condensed water/ice release latent heat into the lower atmosphere. Sensible heat is also released into the lower atmosphere. Being so much warmer than the surroundings, the open water radiates much stronger in the thermal infrared than the surroundings. Infrared imagery from NASA’s MODIS sensor indicate the thin ice and open water having apparent temperatures (brightness temperatures) 20-30 deg. C greater than the surroundings. Clearly, sea ice caps ocean heat from the cold Arctic winter…
Click for a medium resolution version of the above graphic. Image resolution is 1000 m.
MODIS nicely captures the “sea smoke” plumes of condensed water vapor streaming downwind to the south…
Sea smoke to the north of Robeson Channel and Nares St. Image ground resolution is 250 m. Blue and green reflectance is resampled from 500 m resolution data to the 250 m resolution red image.
Polynyi (plural of polynya) are special for additional reasons.
• Sometimes called an “ice factory”, a polynya can produce ice that is continually exported down wind. The ice rejects salt, leading to sinking (more dense than surroundings) salty ‘deep water’. Evaporation cools the surface, helping the cool dense water sink, helping set up a thermohaline circulation.
• Polynyi are wildlife hot spots for beluga whales and narwhals that feed on plankton that can bloom because the ice is thin or absent. The whales can come up for air, reliably in the polynya.
Find an animation of the polynya for the month of March here.