Definition

A water area enclosed in ICE, generally fast; this water area remains constant and usually has an oblong shape; sometimes limited to one side by the COAST. Any enclosed sea water area in PACK ICE other than a LEAD, not large enough to be called OPEN WATER. If a polynia is found in the same region every year, for example, off the MOUTHS of big RIVERS, it is called a recurring polynia. A temporary small clearing in PACK ICE which consists of small ICE FLOES and BRASH ICE in continuous local movement is called an unstable poly­nia; an opening which is flanked by large FLOES and therefore appears to be relatively stable is called a stable polynia. When frozen over, a polynia becomes an ice skylight from the point of view of the submariner.