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Norwegian Sea

NORWEGIAN SEA. The sub-polar regions of the Atlantic lying between the Scandinavian peninsula and Greenland have been in recent years carefully investigated by Norwegian expeditions under Professors Mohn and Sars; and, as the sea immediately to the west of Norway has not hitherto been known by any distinctive name, Mohn has proposed the name of " Norwegian Sea,"—a suggestion which has been now generally adopted. The Norwegian Sea, therefore, includes the whole of the region between Greenland and Norway, a portion of which, to the north-west of the island of Jan May en, is sometimes known as the Greenland Sea. The Norwegian Sea is a well-marked basin cut off from the Atlantic, by submarine ridges connecting the north of Scotland, the Earoe Islands, Ice-land, and Greenland. On the summit of these ridges there is an average depth of about 250 fathoms. Between Spitzbergen and Lapland there is a wide opening into the Barents Sea, where the depth is from 100 to 200 fathoms. Between Spitzbergen and Greenland a wide and deep open-ing extends into the frozen Arctic Ocean, with a depth of 2500 fathoms. The surrounding land is almost everywhere high, rugged, deeply indented with fjords, and skirted with outlying islands, which are mostly composed of stratified rocks and ancient geological formations. Jan Mayen, situ-ated near the centre of the basin, Iceland, and the Faroe Islands are of volcanic origin.

The marked peculiarity of the Norwegian Sea is the striking contrast in the climate of its eastern and western portions. If we draw a line from the east side of Iceland to the south end of Spitzbergen we have, generally speaking, on the west of this line a sea covered with ice during the whole of the year, throughout nearly its entire extent. It is only rarely that the east coast of Greenland can be ap-proached through the lanes and openings formed in the ice. An arctic current passes southward along the coast of Greenland, carrying with it vast fields of hummocky ice, and enters the North Atlantic through the straits which separate Iceland from the coast of Greenland. To the eastward of this line we have a sea free from ice throughout the year. A warm current—the so-called ex-tension of the Gulf Stream—passes between the coasts of Scotland and Iceland, and carries a large amount of heat to the shores of Norway and Lapland, rendering them relatively mild and habitable. The prevailing wind over the western part of the Norwegian Sea is from the north-east, while that over the eastern is from the south-west, in each case corresponding with the direction of the ocean currents. With respect to the relations of the barometric minimum to the prevailing winds and currents see METEOROLOGY, vol. xvi. p. 139.

In March and April a very extensive seal fishery is carried on to the north and east of Jan Mayen along the edge of the ice-fields,—as many as 300,000 young seals having been captured in one season. Large numbers of polar bears are at this time noticed in the neighbourhood of the seal rook-eries, and are captured on the ice at great distances from land. Later in the season there is a right whale fishery to the north and west of the island of Jan Mayen. A large number of small vessels from Hammerfest and Lapland ports visit the coasts of Spitzbergen each season to collect eider-down, and to engage in the walrus and shark fisheries. Narwhals (Monodon) are also captured along the edge of the ice-floes. Guillemots, little auks, gulls, and other sea-birds are found in vast numbers near the coast of Spitzbergen and along the edge of the pack-ice. Along the coast of Nor-way there are valuable cod, mackerel, herring, and lobster fisheries. The Norwegian Sea has a depth almost rivalling that of the great Atlantic and Pacific Oceans, that of the whole of the central parts exceeding 1000 fathoms, while to the south-east of Jan Mayen there is a depth of 2000 fathoms, and off Spitzbergen of 2500 fathoms.

The bottom in the western portion is composed of a mixture of mud and stones formed from the detrital matter carried from the land by floating ice, and containing not more than 5 or 6 per cent, of carbonate of lime. In the deeper parts of the eastern portion we have a fine mud or clay containing sometimes 50 per cent, of carbonate of lime, and a total absence of the ice-borne stones ai»d gravel so abundant in the western portion. The carbonate of lime consists chiefly of the shells of Globigerina which have fallen from the surface, and some other species of Fora-minifera (the most frequent of which is Biloculina) which live on the bottom. In some places this deposit approaches in character the Globigerina ooze or mud of the Atlantic, but is very poor in pelagic shells when compared with the deposits in lower latitudes. The pelagic Foraminifera and Pteropod shells so abundant in tropical parts of the Gulf Stream are killed off and fall to the bottom as they are carried into the colder areas of the North Atlantic. The upper layer of this deposit is of a brownish colour, and is less compact and contains more lime than the deeper layers, which have a blue or greyish colour. In this respect it agrees with the deposits found at similar depths around all continental shores. The deposits along the Norwegian coast, in depths less than 1000 fathoms, consist chiefly of detrital matter from the shores, the mineral particles consisting of quartz, felspars, mica, hornblende, magnetite, and fragments of rocks. Around Jan Mayen and Iceland the deposits consist largely of volcanic sand. In all the deposits there are many Diatom frustules. The isotherms of the atmosphere receive a very remarkable de-flexion to the north along the coast of Norway, as may be seen by reference to the article METEOROLOGY, figs. 8-11 (vol. xvi. pp. 133, 135, 136). A similar remarkable deflexion takes place with the isotherms of the ocean, showing the temperature of the sea surface. In January the warmest water is found at a distance of over 100 miles from the coast, and ranges from 46° Fahr. in the south to 36° Fahr. in the north. In July and August the warmest water is found close along the shore, the range being from 60° Fahr. in the south to 47° Fahr. in the north. This is due to the cooling effect of the

Map of Norwegian Sea.

land in winter and its warming effect in summer. In the western part of the Norwegian Sea ice-cold water is found at the surface, throughout the year. The deeper parts are wholly filled with ice-cold water, this temperature being met with off the coast of Norway at a depth of 400 or 600 fathoms. The remarkably mild and genial temperature of Norway, considering its latitude, is to be accounted for (1) by the warm current from the south which flows north-wards over the banks and fills up the deep fjords beyond with water of a relatively high temperature ; (2) by the banks which extend along its shores with a depth of between 100 and 200 fathoms,— sometimes stretching out several hundred miles from the land and thus keeping the ice-cold water of the basin out of the deep bays and fjords. The water at the bottom of the deep fjords usually ranges from 40° Fahr. to 43° Fahr. throughout the year. In summer the surface is warmer than the bottom water in these fjords, but in winter it is several degrees colder (see NORWAY, p. 580). The bottom water in the fjords is not affected by the cold of winter or heat of summer, owing to the great depth in connexion with the slow rate at which changes of temperature are communicated through the water. The specific gravity ranges from 1' 0265 along the coast of Norway to 1 • 0250 among the ice-floes off the coast of Greenland.

The narrow and deep channel running between the Faroe Islands and Scotland (see fig. 1, p. 564) must be specially referred to on account of the deep-sea investigations which have been there carried on. Indeed the widespread interest taken at the present time in the deep sea arose in a great degree from the interesting discoveries, made in this channel by Dr Carpenter and Wyville Thomson in 1868 and 1869, in H.M.S. "Porcupine" and "Lightning." Two areas were found, one having at the bottom a temperature of 30° Fahr. and the other a temperature of 45° Fahr. The faunas in the two areas were likewise characterized by remarkable differences. There appears to have been no suspicion that a submarine ridge separated the bottom water of the one area from that of the other. The re-searches carried on in H.M.S. "Challenger" showed that in all cases there were indications of submarine ridges separating areas in which a difference of temperature was found at the bottom. In the years 1880 and 1882 this channel was again investigated by H.M.S. " Knight Errant" and " Triton." A ridge, now called the Wyyille Thomson ridge, was discovered running in a north-north-west direc-tion from the north of Scotland to the Faroe banks, and separating the warm and cold areas. The average depth on this ridge is 250 fathoms, but there is a small saddle-back in the northern portion of it with a depth of a little over 300 fathoms. Ice-cold water was traced to the top of this ridge, and through the saddle-back to the south-west margin. Here the cold water is met by the warm current passing to the north-east, a mixture takes place, and the whole flows towards the north-east. No true ice-cold current appears to pass into the Atlantic through the Faroe channel (see the map). That the ridge is swept by strong tidal currents as well as by the steady flow to the north-east is shown by the fact that no fine deposit is allowed to accumulate on it, and by the particles of sand and gravel from the ridge which are spread over the sea-bottom to the north-east. Over the ridge large smooths and well-ings up of water take place at certain times as the great tidal wave passes through this channel into the North Sea. The top of the ridge, which is about 5 miles wide, is covered with gravel and rocks, many of them rolled and glaciated, consisting of granite, gneiss, mica-schists, sandstone, limestone, diorites, &c. On both sides of the ridge a mud is found containing Foraminifera shells, Diatoms, and minute mineral fragments, such as quartz, mica, hornblende, augite, felspars, magnetite, glauconite, &c. Mineral particles from the ridge are much more numerous and larger in the cold than in the warm area, thus indicating the direction in which the currents sweep. The stones resemble those of the Orkneys, and were most probably carried to their present position by glaciers or icebergs during the Glacial period. Since temperature is the most important factor in the distribution of marine species it is not astonishing to find a considerable difference in the fauna on each side of the ridge. Mr Murray states that in the '' Knight Errant" dredgings, of seventy-one species from the warm area and forty-seven from the cold area, the depths being about the same and the distance only about 40 miles apart, there were only two common to both areas. The animals from the cold area are chiefly arctic forms, and re-semble closely those from similar depths off the east coast of North America, while those from the warm area have a southern and abyssal character. We have indeed in the Faroe channel a curious mixture of arctic, abyssal, and modified British faunas, the distribution and limits of which have not yet been worked out. A thorough investigation of this channel in its hydrographical and biological relations is still a great desideratum.

The Norwegian Sea exhibits an abundant pelagic fauna and flora. The warm water of the Gulf Stream very frequently brings to the coasts of Norway animals usually met with only at lower latitudes. Diatoms and other minute Alga? are found in vast banks, especially in the neighbourhood of the melting ice, giving the water a peculiar green colour. This green-coloured water is re-garded by the whalers as one of the best indications of good fishing grounds. Entomostraca, Medusa?, Ctenophora, Siphonophora, Pteropods, and Radiolarians are also to be found in great abundance on the whaling grounds. The deep-sea dredgings of the Norwegians do not show such an abundant or rich fauna as is met with at similar depths in more southern latitudes.

See Wyville Thomson, The Depths of the Sea (2d ed., London, 1874); "Preliminary Report of the Scientific Exploration of the Deep Sea in H.M. Surveying-vessel ' Porcupine' during the Summer of 1869, conducted by Dr Carpenter, Mr J. Gwyn Jeffreys, and Professor Wyville Thomson," in Proc. Roy. Soc., vol. xviii. p. 397 (1S70); The Norwegian North-Atlantic Expedition (1876-78), by Professors Mohn, Sars, and others ; " Exploration of the Faroe Channel during the Summer of 1880, in H.M.'s hired ship ' Knight Errant,' by Staff-Commander Tizard, R.N., and Jotuj Murray, with subsidiary reports by various scientific men," in Proc. Roy. Soc. Edin., vol. xi. p. 638 (1882); and "Remarks on the Soundings and Temperatures obtained in the Faroe Channel during the Summer of 1882," by Staff-Commander T. H. Tizard, R.N., in Proc. Roy Soc., vol xxxv p. 202 (1883). (J. MU.)

The above article was written by: John Murray.

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