The Arctic Sea presents a great contrast between the salinity of the surface of the ice-free Norwegian Sea with 35 to 35.4 and that of the Central Polar Basin, which is dominated by river water and melted ice, and has a salinity less than 25 per mille in most parts.
The Norwegian Sea was of string left in the ball on board.
But detailed studies of the circulation of the water in any small area show deviations from the calculated results that are to be expected: thus Nansen's investigation of the Norwegian sea shows that the main directions of streaming of the water are broken up by numerous large and small vortices.
In the case of the Gulf Stream, which is not much impeded by the land, this descending motion is relatively slight, being perhaps largely due to the greater specific gravity of the water; it ceases to be perceptible beyond about 500 fathoms. On the European-African side the descending movement is more marked, partly because the coast-line is much more irregular and the northward current is deflected against it by the earth's rotation, and partly because of the outflow of salt water from the Mediterranean; here the movement is traceable to at least 1000 fathoms. The northward movement of water across the Norwegian Sea extends down from the surface to the IcelandShetland ridge, where it is sharply cut off; the lower levels of the Norwegian Sea are filled with ice-cold Arctic water, close down to the ridge.
The communication between the Atlantic and Arctic basins being cut off, as already described, at a depth of about 300 fathoms, the temperatures in the Norwegian Sea below that level are essentially Arctic, usually below the freezing-point of fresh water, except where the distribution is modified by the surface circulation.
A cyclonic circulation of the atmosphere is associated with a cyclonic circulation of the water of the ocean, as is well shown in the Norwegian Sea and North Atlantic between the Azores and Greenland.
Higher than that of the open Norwegian Sea between Jan Mayen and the Lofoten Islands.
Denmark Strait is the sea between it and Iceland, and the northern Norwegian Sea or Greenland Sea separates it from Spitsbergen.
It is particularly in evidence round the whole of the Antarctic Shelf, where it occurs down to depths of 2500 fathoms. It is the chief deposit, according to Nansen, of the North Polar Basin and, according to Schmelck and Bdggild, of the Norwegian Sea also, where it is largely mixed with the shells of the bottom-living foraminifer Biloculina.