THE ARCTIC OCEAN The broad outlines of the physical geography of Arctic regions are known, although much has to be done in filling in details. The landlocked Arctic sea or ocean, lying eccentric to the North Pole includes, with the Greenland and Norwegian seas, about 5,400,00osq.m. A feature of the Arctic sea is its wide continental shelf on which lie numerous groups of islands, Greenland, Spits bergen, Franz Josef Land, Novaya Zemlya, the Canadian Arctic islands, etc. (q.v.). No islands are known in the deep polar basin and there is little likelihood of any existing. The tidal observa tions of the "Maud" discourage the probability of any exten sive land in the Beaufort sea, which is the one large unexplored area in which land has been suggested.
The wide continental shelf is marked by several depressions below ioo fathoms. Baffin bay falls to depths of over i,000 fathoms; the Greenland sea, including its south-eastern part which is sometimes called the Norwegian sea, falls to 2,000 fathoms, and the Barents sea, which is really a gulf of the Green land sea, reaches over 30o fathoms in the west. The Kara s' a is a shallow sea scarcely over ioo fathoms in depth between Novaya Zemlya and the Yamal peninsula. The name Beaufort sea applies to that part of the ocean between Alaska and the Parry islands. The Bering sea lies between Bering strait and the Aleutian islands. The deep polar basin has not been accurately charted since its surface is generally ice-covered. The deepest soundings are 2,100 fathoms in 81° N., 130' E. ; 2,020 fathoms in 84° 3o' N., 75° E.; 2,050 fathoms in 87° 43' N.,
20' W.; and 3,076 fathoms in 77° 45' N., i75° W. The last is an echo sounding. A sounding of
fathoms in 72° N. 147° W. sug gests the need of confirmation; it was probably only about 1,383 fathoms. Peary found 1,500 fathoms within five miles of the Pole. The basin of the Greenland sea is cut off from the polar basin by a ridge at about Boo fathoms between Greenland and Spitsbergen. This ridge has not been accurately defined. The Faeroe-Icelandic and Wyville Thompson ridge at less than 300 fathoms separates the deep Greenland sea from the depths of the Atlantic basin. Other connections of the Arctic waters and the great ocean basins are by the many shallow channels among the Canadian Arctic islands and the narrow Bering strait which is only 3o fathoms deep.
The origin of the polar basin is not clear, but there is some evi dence that it is a relatively recent feature of the earth's surface and did not exist in Palaeozoic times. The wide continental shelf is probably a plain of marine abrasion in which the disintegrating power of frost, an active agent of destruction in the Arctic, has helped the action of the waves. If this explanation is true there must have been a change in the relative level of land and sea; either a sinking of the land or a rising of the sea. The lowering of sea-level during the Pleistocene ice age owing to the abstrac tion of water from the oceans offers a partial explanation, but wave and frost action needed a larger period of time than the duration of the ice age. Since its formation began the shelf has been undergoing depression by the weight of land waste accumu lating on its floor, and at the same time denudation, by decreasing the weight of the land, is causing the coastal region to rise. The strandflat, a rocky platform at 6o to 1 oof t. above sea-level, is an other significant feature of many Arctic and sub-Arctic lands. Nansen sees in it another plain of marine abrasion formed when the ocean water stood higher owing to feeble glaciation.
Bottom deposits in high latitudes contain little or ganic matter and only 1 to 4% of
Between Spitsbergen and Greenland the amount of lime increases to over 20 or even 3o% owing to foraminifera. Diatoms which are abundant in sur face waters do not, among the rock waste, form a high enough proportion to justify the name of diatom-ooze for any Arctic deposit.
Arctic surface waters in spite of being cold are relatively light on account of their low salinity, due both to lack of evaporation and steady inflow of great volumes of fresh water from the Eurasian and American rivers. The tendency of the light surface layers is to spread outwards, a movement which is helped by the prevailing winds, and the overflow necessary from a constricted basin to which inflow of river water is considerable and where evaporation is slight. Within the polar basin the sur face waters are sweeping across from Alaska and Siberia towards Spitsbergen and Greenland on the Asiatic side of the Arctic sea. Most of this water and the ice it carries finds its way southwards into the Barents and Greenland seas by the east Spitsbergen and east Greenland currents which flow southward along these coasts and tend to block them with streams of pack-ice. Some of the polar water finds its way out through Smith sound and other channels west of Greenland and feeds the Labrador current along the west of Davis straits and the coast of Labrador. Lastly some of the water finds its way westward through the Beaufort sea and merges again in the great transpolar drift except a little which flows southward on the western side of Bering strait. The Labrador current is dissipated by the Gulf Stream on the Newfoundland banks. The east Greenland current splits, sending one branch eastward to the north of Iceland and the Faeroes, eventually to be lost in the north Atlantic drift, and another round Cape Fare well and northward into Davis strait. In opposition to these cold outflowing currents there are northward setting drifts due to prevalent winds. The most noteworthy is the north Atlantic drift. This washes the coasts of Britain and Norway and has four main branches: (I) the North Cape drift along the Murman coast into the Barents sea; (2) the Spitsbergen drift northward past Bear island and western Spitsbergen; (3) the Irminger current, north westward along the south and west coasts of Iceland into Den mark strait; (4) another north-westerly stream into Davis strait, washing the coasts of south-west Greenland. A small current sets northward along the eastern side of Bering strait. All these cur rents vary in intensity from year to year. The ultimate causes of the variation between inflow and outflow are not clear.
In the polar basin the vertical distribution of temperature and salinity vary little in all places examined. From the surface to ioo fathoms temperature is below the freezing point of fresh water with a minimum of 28.6° or 28.7° (-1.9°C. or —1.8°C.) at 3o fathoms. Salinity increases from 29 or 3o per mille at the surface to nearly 35 at i oo fathoms, and below that depth it seems to remain constant. Temperature rises at 16o or 200 fathoms to 32.5° (0.3°C.) or even 33.8° (i°C.) and then falls to a second minimum of 30.5°
at 1,400 to 1,600 fathoms, below which it rises a few tenths of a degree towards the bottom. There is little variation in these figures in summer and winter, except near the surface, where a relatively fresh layer of 5 to 6f t. may occur owing to melting snow on pack ice. Near the Siberian coast there is in summer a layer of warm surface water from the Siberian rivers which helps to keep those coasts free from ice at that season. In the Greenland and Norwe gian seas the water below about 400 fathoms has a uniform salinity of nearly 35 per mille and a temperature at that depth slightly be low 32°, falling to 29.8° (-1.2°C.) at the bottom. This is the same water that fills the polar basin. The lower temperature at the bottom of the Greenland sea than in the polar basin confirms the existence of a submarine ridge between Greenland and Spits bergen which cuts off the colder bottom water of the Greenland sea. In the Spitsbergen current from the south, maximum surface temperatures of 41° at 42.8° and a maximum salinity of 35 per mille occur west of Spitsbergen. It is this Atlantic water which forms the warmer layer already referred to.
In the Barents sea the Atlantic drift waters have a salinity of nearly 35 per mille and a temperature of 41° to 43° (5° to 6°C.). The bottom temperature in the west and south-west is above 32°. In the eastern part salinity and temperature are lower and the bottom temperature falls below 30.2° (-1°C.).
, The Kara sea, with much river water, has a low salinity of 29 to 34 per mille. Baffin bay like the polar basin has an intermedi ate warm layer between cold surface and bottom layers.
Two-thirds of the Arctic sea is covered by drifting pack-ice which is formed by the freezing of surface layers during autumn, winter and spring. A small part of the ice comes from glaciers. This berg ice is distinguished easily by size and structure from sea-ice. It comes principally from Greenland with some from Franz Josef Land, Spitsbergen, Novaya Zemlya and Elles mere island, but large icebergs, except in west Greenland waters, are rare in the Arctic. Pack-ice seldom grows thicker than 6 to 7f t. in one year, but by yearly accretions it may attain I 5f t. or more. Floes are generally covered with sufficient weight of snow to depress the actual surface of the ice to sea-level. Pressure due to currents and wind may cause piled or rafted hummocks 4o to Soft. above sea-level. Nares' palaeocrystic ice was probably rafted ice mixed with floe-bergs from glaciers but was not more than four or five years old. There is some surface melting by solar radiation in summer, but it is only by drifting into warmer waters that much ice is destroyed. Apart from actual melting under those conditions the floes become soft and friable and easily disintegrate under wave action. All polar ice is in motion even in mid-winter and lanes and pools frequently appear between the floes.
Life.—Those parts of the ocean continually covered with ice have a poor development of surface plant life, due prob ably to a lack of light, and a consequent poor development of animal life. The deeper strata are also poor in individuals though fairly rich in species. Where the sea is more open plant life teems in the surface waters to such an extent that diatoms sometimes tinge the sea bright green. This abundant phytoplankton is due to a combination of conditions. Warmer deep layers of water in which nitrates and carbon dioxide set free by animal metabolism rise to the surface in polar seas and afford food for pelagic plants, while the low temperature of the waters retards the actions of denitrifying bacteria. Animal plankton is less abundant, but in all shallow seas there is an abundant bottom fauna. The occur rence and erosive action of ice impedes the growth of a littoral fauna and flora on many coasts. Fishes are numerous, including a species of sea char or salmon, cod and halibut. Seals are abun dant, especially along the margins of the drifting packs. Whales have been much reduced in number by hunting, but still occur outside the pack. In the ice-covered seas mammalian life is scarce except for a few seals, an occasional narwhal and a few wander ing polar bears, but the Arctic is not a lifeless desert.
