Polar ice

“ Some of the sealers ascribed this obstinacy in the bay-ice to its greater thickness; believing that the shallowness of the water had favoured a frozen formation below, that did not so much prevail off soundings. This theory may have been true, though there was quite as much against it, as in its favour, for polar ice usually increases above and not from below. The sea is much warmer than the atmosphere, in the cold months, and the ice is made by deposites of snow, moisture and sleet, on the surfaces of the fields and bergs. ”

“ How shall we account for the masses of polar ice, for the immense icebergs, and the glaciation of Greenland? The snowfall of the polar regions is light. The air is nowhere drier than over the cold glacier ice, as is proved every day in Switzterland by the quickness with which clothes dry when hung over it. At the same time the ice is covered with extremely fine, hardly visible snow crystals. If we boil water in a retort which is connected with another vessel containing a piece of ice, all the steam will pass over on to the ice and deposit itself as ice upon it. ”

“ Fresh snow is all the while falling, and adding to the whole. Blizzards come and drive the powdery loose snow from one place to another, and the hard-driving wind binds the powder into solid ice. Imagine all this on an enormous scale! Not over an area of a dozen or a hundred, or even a thousand square miles, but over an area as large as Europe and Australia combined, then we have a picture of what is happening over the length and breadth of Antarctica! The ice thus accumulated from snowfall, thus consolidated from loose snow into solid ice by pressure, gets pushed ultimately into the sea. ”

“ In order fully to appreciate the power and magnitude of this ice-movement, it must be borne in mind that a very large proportion of the ice is of very ancient formation,—old floes or ice-fields of immense thickness and miles in extent, as well as of icebergs discharged from Humboldt Glacier. These vast masses, tearing along with the current in the early winter through the sea as it is closing up and new ice is making rapidly, are as irresistible as a tornado among the autumn leaves. ”

“ The ice of the polar sea is not an immovable surface. Twenty-four hours—or even twelve hours—of strong wind, even in the depth of the coldest winter, will set the big floes grinding and twisting among themselves, crushing up into pressure ridges in one place, breaking into leads in another place. ”

“ Innumerable conversations during a number of years with all kinds of intelligent, well-read people have shown me conclusively that outside of the scientist, the geographer, and those who have made a study of polar exploration, the average person has no idea whatever of the real character of polar ice. ”

“ During the summer the floe-ice decreases again by melting partly on the surface owing to the direct radiation of heat from the sun, partly on the under side owing to the higher temperature of the water in which it floats. The first kind of melting is that which prevails in the North Polar Basin, which the second occurs in more southern latitudes. The floe-ice is constantly more or less in movement, carried by winds and currents. The changing wind, and also to a great extent the changing tidal current, causes diverging movements in the ice by breaking it into larger or smaller floes. ”

“ It is more commonly used to describe huge floating masses of ice that drift from polar regions into navigable waters. They are occasionally encountered far beyond the polar regions, rising into beautiful forms with breakers roaring into their caves and streams of water pouring from their pinnacles in the warmer air. When, however, they rest in comparatively warm water, melting takes place most rapidly at the base and they frequently overturn. Only one-ninth of the mass of ice is seen above water. ”

“ This broken-up ice is known as "Pack ice." During the breaking up of the ice, the floes crush together and their edges are broken and curled and piled with the pressure. Farther away from the open sea, well in among the solid floes, this pressure is very heavy and one floe may run over and another under the other. The edges of an extended crack, that has formed in a weak place, curl over and over and a long ridge of broken-up ice is the result. ”

“ During the winter, frost and snow thicken them, and wind piles them into hummocks. Sometimes part of the ice lasts for more than one year—thus whalers talk of ice of one or more seasons old. But the floes of the Polar Sea are perennial. They bear the plainest evidences of great age. They grow from above, and are stratified by seasonal deposits of snow slowly converted into ice. Excepting in insignificant spots along shore, the surface of the Polar Sea never freezes into new floe; it is never long enough exposed. ”

“ As winter sets in within the Arctic Circle, the sea which flows between the northern coasts of Europe, Asia, and America becomes covered with ice to the shores, thus forming an enormous field of ice some two thousand miles across. This, lying on the surface of the water, often having a thickness of from thirty to fifty feet, checks, but cannot control the tides. The ebb, on one hand, leaves vast tracks of ice, previously afloat, straining on the ground, cracking so as to form enormous fissures and weakening the surface resistance. ”

“ Sea ice is often pressed together so as to form great torosses or ice-casts, formed of pieces of ice which at first are angular and piled loose on each other, but gradually become rounded, and freeze together into enormous blocks of ice, which, together with the glacier ice-blocks, form the principal mass [pg 426] of the ground ice found on the coasts of the Polar lands. The water which is obtained by melting sea-ice is not completely free from salt, but the older it is the less salt does it contain. ”

“ Those parts of the external world from which the influence of the sun is withdrawn for the greatest length of time thus become intensely cold, excepting in the immediate vicinity of the polar openings, where the issue of warm air, from the internal cavity, tempers the atmosphere: but at a short distance from the verge of the opening the very influence of this warm air generates cold, by parting rapidly with its latent heat and condensing into snow and hail, which causes the circle of ice between [146] the 70th and 80th degrees of latitude, called the “icy hoop.” ”

“ We can well enter into the disappointment of those who expected to have found the long-talked-of open Polar Sea, instead of which ice, evidently of great age and thickness, the accumulation, it might be, of centuries, and resembling rather low floating icebergs massed together, than the ordinary appearance of salt-water. ”

“ Bearing these facts in mind, the reader will perceive that it is the surface-water only which ever reaches so low a temperature that it is changed to ice; and he will also perceive that when the wind moves the surface-water, the particles which have become chilled by contact with the air mingle in the rolling waves with the warm waters beneath, and hence that ice can only form in sheltered places or where the water of some bay is so shoal and the current so slack that it becomes chilled to the very bottom, or where the air over the sea is uniformly calm. ”

“ Ice being a bad conductor of heat, likewise limits the process of congelation; for after attaining a thickness of ten or fifteen feet, its growth is very slow, and probably even ceases altogether; for when floating fields, or floes, are found of a greater thickness, this increase is due to the snow that falls upon their surface, or to the accumulation of hummocks caused by their collision. ”

“ The temperature has risen again, and the roof over the upper deck gives us once more a worse than tropic shower. The snow next the ice grows more slushy, and this I am more than ever puzzled to understand, since I have found to-day that the ice, two feet below the surface, has a temperature of 20°; at the surface it is 19°, and the snow in contact with it is 18°. The water is 29°.
The darkness is not yet quite absolute. ”

“ At length we managed to gain their attention, and were informed that, as soon as the wind should blow strong from the land, the ice might be expected to remove from the shore, so as to open a passage for boats, and that it would remain in the offing until the reappearance of the stars. "Further to the westward," they continued, "the ice often adheres to the land throughout the summer; and when it does break away, it is carried but a short distance to seaward, and is brought back whenever a strong wind blows on the coast. ”

“ Undoubtedly the coldest spot in the world is to be found in the center of the great ice during the polar night, where at an altitude of one or two miles it gets the full benefit of the frigid polar air; is several hundred miles from the polar seas, and is insulated by a mile or more of ice and snow from any radiation of heat from the earth beneath. ”

“ Having reached the end of Nansen Sound, with Svartevoeg on my left, and the tall, scowling cliffs of Lands-Lokk on [Pg 196] my right, I viewed for the first time the rough and heavy ice of the untracked Polar sea, over which, knowing the conditions of the sea ice, I anticipated the most difficult part of our journey lay. Imagine before you fields of crushed ice, glimmering in the rising sunlight with shooting fires of sapphire and green; fields which have been slowly forced downward by strong currents from the north, and pounded and piled in jagged mountainous heaps for miles about the land. ”

“ Then comes a whole winter's intense frost, snow falls and adds to the weight and thickness, and when this ice breaks up the following spring we have a really formidable pack to encounter. When such pack ice is not very open, but still open enough for a protected ship to work its way through, the ship has to be handled with the greatest care even when navigating through it in fine weather. This ice cannot be charged indiscriminately like one-year ice, and one must be able to distinguish between one piece of ice and another. ”

“ It can be seen that this ice is much more plastic than fresh-water ice. Fresh-water ice is relatively brittle, even in thin layers. Fresh-water ice, of the thickness of about 21⁄2 or 3 inches, will bear the weight of a man, but a child's foot would sink through sea ice of similar thickness, as if going through a layer of tough glue. ”

“ Frequent falls of snow, combined with alternate melting and freezing in summer, and a process similar to the upbuilding of glacial ice, are mainly responsible for the growth in thickness of the ice on the Polar sea. ”

“ In the higher altitudes and in the polar latitudes where glaciers are chiefly generated, the mean annual temperature of the surface is usually below the melting-point of ice. Here the temperature of the ice between the top and bottom of the zone of constant temperature must, on the average, be below the melting-point, unless heat enough is generated in the interior of the ice to offset the effect of the temperature above. ”

“ In the Antarctic Regions almost all the ice floating in the sea, whether land or sea ice, is covered at sea-level with a light wash of yellowish brown or yellow ochre. The bergs are coloured by it as well as the pack ice, where the ice is lapped by the sea. When a ship charges against a piece of one-year pack ice, the ice is easily broken and often breaks not only vertically, but horizontally. ”

“ In low temperature new ice forms rapidly. This offers an obstruction to the drift of the old ice. As the heavy central pack is pressed against the unyielding land pack the small ice is ground to splinters, and even heavy floes are crushed. This reduced mass of small ice is pasted and cemented along the shores of the Big Lead, leaving a broad band of troublesome surface as a serious barrier to sled travel. It seems quite probable that this lead, or a condition similar to it, extends entirely around the Polar sea as a buffer between the land and the middle pack. ”

“ Here the pack of the central polar sea meets the land-adhering ice. The movement of the land pack is intermittent and usually along the coast. The shallows, grounded ice and projecting points interfere with a steady drift. The movement of the central pack is quite constant, in almost every direction, the tides, currents and winds each giving momentum to the floating mass. The lead is thus the breaking line between the two bodies of ice. It widens as the pack separates, and narrows or widens with an easterly or westerly drift, according to the pressure of the central pack. ”

“ The closeness and quantity of the ice in the Polar Seas vary much in different years; but, should it be in the same state that we found it, I would not recommend a ship's leaving Icy Cape earlier than the middle of August, for after that period the ice was not only broken up within the sphere of our vision, but a heavy swell rolling from the northward, indicated a sea unsheltered by islands, and not much encumbered by ice. ”

“ Such is the terrible aspect in which field-ice is seen when broken up and converted into smaller masses or floes. When these lie closely together the mass is called pack-ice; in which shape it usually drifts away with the southern currents, and, separating as it travels south, is met with in loose floating masses, of every fantastic form. There is always, as we have said, a large quantity of floe and pack-ice in the polar seas, which becomes incorporated with the new ice of the succeeding winter ”