THE POLAR GLACIERS

Taranaki Daily News, Volume LV, Issue 258, 22 March 1913, Page 2 (Supplement)

THE POLAR GLACIERS

AN INTERESTING THEORY. An ingenious hypothesis in regard to the history of continental glaciers and their relation to atmospheric phenomena has been worked out by Professor W. H. Hobbs. There are at present two of these glaciers, one of which covers Greenland and the other Antarctica, These great ice sheets differ in many important particulars from the mountain glaciers of lower latitudes. In the latter the land surface always projects above the highest levels of the ice and snow, the glaciers occupying only the hollows and troughs of the mountain slopes. The continental glacier, on the other hand, blankets practically the entire rock surface, except at the margin forming a flat dome; its model is independent of its basement; and its movement is independent of the grades of the underlying dorr. A peculiar system of winds prevails over each of the polar ice caps, in which the distribution of barometric pressure appears to play no part. The winds blowradially outward from the. centre of the polar continents, i.e., they flow down the ice slopes, often with great violence, usually ol sufficient strength to lift the dry granules of snow a couple of feet or more in the air, when the wind develops greater strength the drifting snow rises to the height of a man, and during the characteristic polar blizzards is probably carried to heights of 100 ft or more above the ice surface; yet the direction is always and invariably outward from the centre of the dome. On the other hand, the upper currents as shown, for example, by the drift of smoke from the volcano Erebus, in the Antarctic, and by the movement of cirrus clouds, are in the opposite direction, i.e., fcojvards the interior of the continent. Normally drifting from the north-west, when the outward flow of surface air assumes great, violence, the smoke of Erebuc swings round and moves directly south, with an accelerated velocity, as if the upper air was being drawn strongly inward to replace outward movements in lower levels. These wind systems are explained as follows: Each of the great ice sheets cools the air in contact with it, and the cold and heavy air drains down the slopes of the polar continent. The upper air is drawn down in the, central vortex to replace it. This air comes from a region charged with ice particles, i.e., from the level of the cirrus clouds. The descending air warms adiobatically," according to a well-known law; ice content is melted and vaporised, only to be condensed again when the cold surface of the glacier is approached. Thus the glacier is fed entirely by the moisture of the upper air. This is the opposite process that occurs in the case of mountain glaciers. In the latter the surface winds blowing up the slopes are adiabetically cooled, and the glacier is fed by the moisture which they discharge. The fine dry snow deposited over the interior of the continental glacier is continually swept down the slopes, forming the rounded, dome-like surface. According to this view, the old theory of two polar anti-cyclones must give place to that of two continental (glacier) anti-cyclones, the centre of which—the wind poles of the earth—are not coincident with the geographic poles. Tn Pleistocene times the vastly larger ice sheets must have given rise to correspondingly vaster permanent, anticyclones. Direct evidence of a Pleistocene anti-cyclone has been obtained by Professor Solger, of Berlin, who in studying the fossil sand dunes of the North German plain has shown that the prevailing winds at that time came not from the west, as they do to-day, but from the east.