English

A condition of RADIANT ENERGY in which the VIBRATIONS take place in a regular manner, as in a straight line, circle or ellipse, in a plane perpen­dicular to the path of travel.

Either of the two points of intersection of the surface of a sphere or SPHEROID and its AXIS. The origin of a system of POLAR COORDINATES. Either of the two MAGNETIC POLES of a MAGNET. A long slender rod, as of timber or metal. Such a rod used for SOUNDING is called SOUNDING POLE.

Either of the two points of intersection of the CELESTIAL SPHERE and the extended AXIS of the EARTH, labelled N or S to indicate either the north celestial pole or the south celestial pole.

Either of the two points of intersection of the surface of the EARTH with its AXIS, labelled N or S to indicate either the north geographical pole or the south geographical pole.

The direct or indirect alteration of the physical, chemical, thermal, biological or radioactive properti­es of any part of the environment in such a way as to create a hazard or potential hazard to the health, safety or welfare of any living species.

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.

A small body of still water of artificial forma­tion, its BED being either hollowed out of the SOIL or formed by embanking and damming up a natural HOLLOW.

A small body of still or standing water, perma­nent or temporary; chiefly one of natural formation. A deep or still place in a RIVER or STREAM. In ice terminology, any enclosed relatively small area in PACK ICE, drift ICE, other than a LEAD. See POLYNIA.