A type of air mass with characteristics developed mostly in winter over arctic surfaces of ice and snow. Arctic air is cold aloft and extends to great heights, but the surface temperatures are often h
igher than those of polar air. For two or three months in summer arctic air masses are shallow and rapidly lose their characteristics as they move southward.
The water mass formed in the Arctic Ocean by a combination of freezing on the arctic shelf and deep winter convection in the Greenland and Norwegian Seas. Freezing increases the salinity under the ice
; the dense water sinks to the ocean floor and leaves the arctic basins to enter the Greenland and Norwegian Seas, where it mixes with water that sinks under the influence of surface cooling. The resulting water mass has a salinity of 34.95 psu and a temperature of -0.8 to -0.9C. It fills the Arctic Ocean at all depths below 800 m, the sill depth to the Atlantic. It enters the Atlantic in bursts, when the passage of atmospheric depressions lifts the thermocline and allows Arctic Bottom Water to flow over the sill. Overflow events in the Denmark Strait and across the Iceland-Faeroe sill contribute some 5 Sv (5 x 10^6 m3/s) to the formation of North Atlantic Deep Water.
The line of latitude 66 deg 34 min N (often taken as 66N). Along this line the sun does not set on the day of the summer solstice, about June 21, and does not rise on the day of the winter solstice, a
bout December 22. From this line the number of twenty- four-hour periods of continuous day or of continuous night increases northward to about six months each at the North Pole.
Latitude of 66.5 North. The southern limit of the area of the Earth that experiences 24 hours of darkness or 24 hours of day at least one day during the year.
"Any area in the high latitudes dominated by bare rocks, ice, or snow, and having a sparse vegetation and a low annual precipitation." [from Glossary of Arctic and Subarctic Terms (1955)]. Thus stated
, this includes portions of both ice cap and tundra regions of both hemispheres. The term barrens is sometimes used, but this has more general application.
The semipermanent, semicontinuous front between the deep, cold arctic air and the shallower, basically less cold polar air of northern latitudes; generally comparable to the antarctic front of the Sou
thern Hemisphere.
Haze in Arctic regions which reduces horizontal and oblique visibility and which may extend to a height of about 10 km. It appears blue-grey when viewed away from the Sun, and reddish-brown toward it.
A weak high that appears on mean charts of sea level pressure over the Arctic basin during late spring, summer, and early autumn. (Also called arctic anticyclone, polar anticyclone, polar high.)
A water mass identified by a salinity minimum found at a depth of about 800 m in the North Atlantic Ocean. It is formed in two varieties in the Labrador Sea and in the Iceland Sea, from where it sprea
ds southward but is quickly absorbed by North Atlantic Deep Water. The equivalent water mass in the Pacific Ocean is known as Subarctic Intermediate Water.