Antarctic ice sheet

“ That the Antarctic continent, if it exists—it may be an archipelago—is covered with a thick ice-sheet there can be no doubt; but that the character of the land differs from that of Greenland is evident from the table-shaped form of the icebergs, so different from the rugged masses met with in the Arctic seas. From the purely scientific -standpoint it would be of the highest interest to ascertain the nature of the fossil plants which exist in the Antarctic land, if, indeed, there are any. That Greenland, even in the tertiary age, had a climate like that of Southern Europe, has been demonstrated ”

“ East Antarctica is colder than West Antarctica because of its higher elevation; Antarctic Peninsula has the most moderate climate; higher temperatures occur in January along the coast and average slightly below freezing Terrain: about 98% thick continental ice sheet and 2% barren rock, with average elevations between 2,000 and 4,000 meters; mountain ranges up to nearly 5,000 meters; ice-free coastal areas include parts of southern Victoria Land, Wilkes Land, the Antarctic Peninsula area, and parts of Ross Island on McMurdo Sound ”

“ Meager as this information is, it is about all we know of the surface of the globe within the Antarctic circle; and it will be extremely difficult to learn much more. In a latitude much farther from the pole than that where in the north vegetation is abundant, and men and animals live all the year round, the severity of the Antarctic climate cuts off all life, and constantly seals the water under a cap of ice. The coasts and outlying islands thus far examined appear to be wholly volcanic, often composed of nothing but alternate layers of ashes and ice ”

“ Pack ice composed of broken-up sea-ice and fragments of icebergs appears to form a floating breakwater round the Antarctic area. It is penetrated by powerful steamers with ease or with difficulty according to the action of the wind which loosens the pack when it drives it towards the open sea, and closes it up when it drives it against a coast or a barrier of fast ice. At every point but one around the circumpolar area the pack, be it light or dense, appears to extend up to the southern permanent ice or land, though, as in the Weddell Sea, the pack seems at times to be driven bodily away. ”

“ The absence of strong winds has the additional effect of allowing the ice to accumulate in masses, undisturbed. Then great quantities of ice sweep along the coast from the east under the influence of the prevailing current, and fill up the bight of the Weddell Sea as they move north in a great semicircle. Some of this ice doubtless describes almost a complete circle, and is held up eventually, in bad seasons, against the South Sandwich Islands. The strong currents, pressing the ice masses against the coasts, create heavier pressure than is found in any other part of the Antarctic. ”

“ It may be that existing geographical and physical conditions are there such potent agents in producing a state of glaciation that no change in the phases of precession would materially affect it. Still, as the climate of the whole southern hemisphere is dominated by the great mass of ice within the Antarctic circle, it seems probable that if the winter were shorter and the summer longer the quantity of ice would slightly diminish ”

“ As a rule great sheets spread over the seas which fringe the Antarctic continent in the autumn, grow thicker and thicker during the winter and spring, and break up when the temperatures of sea and air rise in summer. Such is the ice which forms in normal seasons round the shores of McMurdo Sound, and up the coast of the western mountains of Victoria Land. In sheltered bays this ice will sometimes remain in for two years or even more, growing all the time, until some phenomenal break-up releases it. ”

“ The ice-hearing currents from the Antarctic regions.—On either side of this warm current that escapes from the intertropical parts of the Indian Ocean, but especially on the Australian side, an ice-bearing current (Plate IX.) is found wending its way from the Antarctic regions with supplies of cold water to modify climates and restore the aqueous equilibrium in that part of the world. There is a general drift up into the South Atlantic of ice-bearing waters from Antarctic seas. ”

“ They rise almost without a break to a height of thirteen thousand feet. Between us and them is the Barrier to the south, and the sea to the north. Unless a blizzard is impending or blowing, they are clearly visible, a gigantic wall of snow and ice and rock, which bounds our view to the west, constantly varied by the ever-changing colour of the Antarctic. Beyond is the plateau. ”

“ The whole makes a tricky place on which to walk in the dark, for the surface is strewn with boulders of all sizes and furrowed and channelled by drifts of hard and icy snow, and quite suddenly you may find yourself prostrate upon a surface of slippery blue ice. It may be easily imagined that it is no seemly place to exercise skittish ponies or mules in a cold wind, but there is no other place when the sea-ice is unsafe. ”

“ At the period of maximum glaciation the climate was much milder, and as the severity of the temperature, due to less precipitation, increased, there must have been sterile ice conditions, and consequent retirement of glaciers and ice-fields. These receding glaciers do not supply bergs; and as the Antarctic icebergs are by far the largest in the world, their origin must be from some other source. ”

“ Thus from such parts of the coast only the largest bergs, which require a deep sea to float them, are moved by the under-currents into the temperate latitudes. Therefore, it happens that, while an ice period progresses, and the antarctic icebergs increase in size, the more readily the cold, deep under-currents force them into the temperate zone, in opposition to the winds and surface currents. ”

“ This hypothesis is supported by the fact that at present winter in the Southern hemisphere coincides with the earth's position in its orbit farthest from the sun, and the ice around the south pole extends much farther toward the equator than that around the north pole, the antarctic ice extending as far as the sixty-seventh degree of latitude. The antarctic summers are also said to be more humid, cold, and chilly than the arctic summers. ”

“ To know that there is always in readiness a perfect supply of the most excellent fresh water is one of the greatest boons to ships navigating in the Arctic Regions, and a luxury which is forbidden to ships navigating in other seas. In the Antarctic, since one seldom or never meets with such pools, one has to pick out a nice old hummocky piece of sea ice or a bergy bit that has been chipped off one of the great bergs, and take some boat-loads of this ice on board. The ice is put into large tubs or barrels, and steam is blown through. ”

“ Critical as our position was, we were cheered by the thought that we were still getting south, but the sledges were being badly damaged by the continual ice-work, and as there were still 340 geographical miles between us and the Pole, we longed for a surface which was a little less like walking over a cucumber-frame. Of all the surfaces on which to travel, none can be more irritating than that of rotten ice through which one's feet are everlastingly breaking. ”

“ Many places in the panorama we have examined show black rock, and the cape on which we stand exposes at times more black than white. This fact always puzzles those who naturally conclude that all the Antarctic is covered with ice and snow. The explanation is simple, that winds of the great velocity which prevails in this region will not only prevent snow resting to windward of out-cropping rocks and cliffs, but will even wear away the rocks themselves. ”

“ The structural composition of ice is a study in itself. To the cursory glance a piece of glacier-ice appears homogeneous, but when dissected in detail it is found to be formed of many crystalline, interlocking grains, ranging in size from a fraction of an inch to several inches in diameter. A grain-size of a half to one inch is perhaps commonest in Antarctic glacier-ice.
The history of Antarctic glacier-ice commences with the showers of snow that fall upon the plateau. The snow particles may be blown for hundreds of miles before they finally come to rest and consolidate. ”

“ March 17.—The storm is still raging; the sky, and even the snow seems black under the inky gloom. The temperature has risen nearly twenty degrees in twenty-four hours, which is a very remarkable phenomenon for the antarctic. The sky in the north-north-east is almost constantly black, indicating what we believe to be open water in that direction. From the ease with which the swell comes in under the pack, and the frequent zones of water-sky, we estimate that we are within fifty miles of the open ice-free ocean ”

“ West of Cape Bird are some small penguin rookeries, and high up on the ice slopes could be seen some grey granite boulders. These are erratics, brought by ice from the Western Mountains, and are evidence of a warmer past when the Barrier rose some two thousand feet higher than it does now, and stretched many hundreds of miles farther out to sea. But now the Antarctic is becoming colder, the deposition of snow is therefore farther north, and the formation of ice correspondingly less. ”

“ Of course for the most part the land is covered to such a depth by glaciers and snow that no wind will do more than pack the snow or expose the ice beneath. At the same time, to visualize the Antarctic as a white land is a mistake, for, not only is there much rock projecting wherever mountains or rocky capes and islands rise, but the snow seldom looks white, and if carefully looked at will be found to be shaded with many colours, but chiefly with cobalt blue or rose-madder, and all the gradations of lilac and mauve which the mixture of these colours will produce. ”

“ The ice directly produced by the freezing of sea-water is never of great thickness, but this thickness increases on one side by the accumulation of snows on its surface, and on the other by the heaping of blocks during the pressure. These mechanical phenomena are able to form slabs eight metres in height. The pressures are produced, in the regions explored by the Belgica, by the wind, which is thus foretold: In summer, during calm weather, there is always a change in the ice-pack, which is accompanied by a formation of cracks and leads. ”

“ The actual direction of this circulation is strongly modified by the influence of the earth's rotation. The existence of a layer of water of low salinity at a depth of 500 fathoms in the tropical oceans of the southern hemisphere is to be referred to this action of the melting ice of the Antarctic regions. Pettersson's view that ice-melting dominates the whole circulation of the oceans and regulates in particular the currents of the seas round northern Europe must, however, be looked on as carrying the explanation too far. ”

“ The skirts of the Antarctic Continent had proved to be rich in minerals wherever the rocks could find a place to penetrate through the gigantic burden of ice, and the principal nations had quarreled over the possession or control of these protruding bits of wealth-crammed strata. But behind the bordering cliffs of ice, rising in places a thousand feet above the level of the sea, and towering farther inland so high that this region was, in mean elevation, the loftiest on the planet, nothing but ice could be seen. ”

“ These originate when shelf ice, such as that found on the northern coast of Greenland and in the bays of Ellesmere Island, breaks up. As a rule, Arctic ice islands are not as large as the tabular icebergs found in the Antarctic. They attain a thickness of up to 55 meters and on the average extend 5 to 7 meters above the sea surface. Both tabular icebergs and ice islands possess a gently rolling surface. Because of their deep draft, they are influenced much more by current than wind. Arctic ice islands have been used as floating scientific platforms from which polar research has been conducted. ”

“ 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. ”

“ I myself think this doubtful, and I am, I believe, the only person living who has seen the Ross Sea open in mid-winter. This was on the Winter Journey undertaken by Wilson, Bowers and myself in pursuit of Emperor penguin eggs—but of that later.
It is clear that winds and currents are, broadly speaking, the governing factors of the density of pack-ice. By experience we know that clear water may be found in the autumn where great tracts of ice barred the way in summer. The tendency of the pack is northwards, where the ice melts into the warmer waters. ”

“ Thus the surface waters moving from the north in order to gain the higher latitudes, after entering the westerly wind-belt, are moved in drift currents by the impelling winds easterly over many degrees of longitude, and also at the same time slowly southward among the cooling icebergs, because of the attraction caused by the difference of temperature and density between the northern drift waters and the icy seas of the antarctic ice barrier. ”