The polar regions: The dynamic and crucial engine of global climate

“ View the arctic and antarctic regions, those huge voids, where nothing lives; regions of eternal snow: where winter in all his horrors has established his throne, and arrested every creative power of nature. Will you call the miserable stragglers in these countries by the name of men? ”

“ In the study also of the climates of the earth, and their effects upon life, we find the ocean bears a most important part. As the circulation of the atmosphere mingles the heated air from the equator with that of the frozen regions of the poles, so the currents of the ocean circulate about the earth, blending the contrasts of climate, and making a harmonious whole of all the different portions. ”

“ It is the means by which the world is kept cool enough for man and beast to dwell in. The polar regions—north and south—are, as it were, the world’s refrigerators; tempering the heated air of the south, and, in connection with the torrid zone, spreading throughout the Earth those beneficial influences which gladden the sphere of man’s temporal existence.
Chapter Eleven. Ice an Agent in transporting Boulders—How this comes about—Dr Kane’s Observations—Long Night in Winter and Long Day in Summer—Extreme Darkness—Influence on Dogs—Intense Cold—Effect on the Sea. ”

“ Now all the land that lies under the zones between the hot and the cold belts can be occupied; but it is likely that owing to location the lands differ somewhat, so that some are hotter than others; the hottest being those that are nearest the torrid belt. But lands that are cold, like ours, lie nearer the frigid zones, where the frost is able to use its chilling powers. ”

“ The task of giving climate its proper place as a factor controlling the life of man as a whole is a difficult one, which can not be definitely and satisfactorily solved to-day—or to-morrow.
Climate and Habitability.—Climate determines where, as well as how, man shall live. It classifies the earth's surface for us into the socalled habitable and uninhabitable regions. The deserts of sand and the deserts of snow and ice, whether the latter be near sea-level or high up on mountain tops, are alike climatic, the former because of aridity, the latter because of cold. ”

“ But the heated air, which has risen in immense volumes in the tropics, spreads out to the north and the south in the upper regions, passes entirely over the trade-winds, and comes down to the earth in the temperate zones. It, however, continues to have the velocity toward the east which it acquired at the equator, and, when it strikes the slower-moving latitudes, it will be traveling much faster than the regions it comes down upon. Hence the westerly winds that prevail almost constantly in the middle latitudes. ”

“ The philosopher of civilization, has discovered that breath, the fan-wafted breeze, the air confined in vessels, the air moving in ventilation, that these are all parts of the great body of air which surrounds the earth, all in motion, swung by the revolving earth, heated at the tropics, cooled at the poles, and thus turned into counter-currents and again deflected by a thousand geographic features, so that the winds sweep down valleys, eddy among mountain crags, or waft the spray from the crested billows of the sea, all in obedience to cosmic laws. ”

“ From the north and from the south cold air flows down into the regions of warmer climate. These [Pg 42] polar winds are not so important to sea commerce, but they do a great work in tempering the heat in the equatorial regions. We cannot know how much our summers are tempered by the cool breath of winds that blow over polar ice-fields. And the cold regions of the earth, in their brief summer, enjoy the benefits of the warm breezes that flow north and south from the heated equatorial regions. ”

“ Even the great deserts, which appear so useless to man, and which are uninhabitable to a great extent, have their office, and an important one too; they are to the earth what ventilators are to buildings, drawing the cold air from the poles to cool the regions that are too hot, and sending a current of heated air through the upper regions of the atmosphere (where it can do no injury to anything) to warm the colder parts of the earth, another instance of the wonderful care and goodness on the part of the Creator. ”

“ But if it be impossible to ignore History in the teaching of Political Geography, it is just as impossible to exclude from our attention great physical features and characteristics. Surface-configuration, climate, and natural products all claim our attention. It is obvious, in fact, that the proper study of Political Geography must give us at least a general notion of the configuration, the river-systems, and climatic conditions of many different lands. ”

“ But when the land-masses became more and more consolidated, when owing to the growth of the continents the warm ocean-currents found less ready access to arctic regions, then the temperature — 379 — of those regions was gradually lowered, until eventually the seas became frost-bound, and the lands were covered with snow and ice. But while the chief determining cause of climate has been the relative distribution of land and water, it is impossible to doubt that during periods of high eccentricity of the orbit, the climate must have been modified to a greater or less extent. ”

“ Regions that have sometimes been frozen and cold have become warmer, and have covered themselves now with oceans, and now with -33- forests, and now with deserts. There is no corner of the whole world which has not undergone changes of climate. ”

“ And on the scarred and grooved rocks was the final evidence; for these deep scratches had surely been ground by the advancing glacier as it slowly and silently moved onward. “The idea that such phenomena were not restricted to regions where glaciers now are found, but that traces of glacial action could be seen over enormous tracts of the earth’s surface, perhaps including regions in the tropics, and that in countries now temperate there might be discovered, not only the remains of tropical fauna and flora, but also distinct indications of a period of arctic cold—this was as new as startling.” ”

“ We must know not only the warm seas, but the cold as well. There is a constant interchange between the water of the tropics and that of the poles, just as there is an interchange of the winds. The cold, ice-laden waters have a tendency to flow into the warmer regions. ”

“ If warm, moist winds constantly blow over a country, they give it a mild climate.
For Recitation.—What does the sun do for the earth? What is meant by the climate of a country? What part of the earth has the most heat and rain? What are the coldest parts of the earth? What kind of climate do you find in the temperate zones? In which zone do you live? In what direction would you travel to reach the Torrid zone? The South Temperate? The North Frigid?
LESSON XIII.
PLANTS.
Preparatory Oral Work.—Talk to class about the care and cultivation of plants. ”

“ The winds have much to do with the climate. The southern half of the continent receives the warm winds from over the Gulf of Mexico, These bring an abundance of rain. The middle portion is swept by winds from the Pacific ocean, but much of the rain is kept out by the mountains along that coast. In winter, cold winds from the Arctic ocean sweep over the level part of the continent and make the climate very cold.
3. Mountains and Plateaus.—The entire western half of North America is a great plateau region called the Pacific highlands. ”

“ Since climate is pract! cally determined by the temperature and moisture of t wr, and since these are dependent on the prevailing winds wmci come charged with the temperature and moisture of the regions they have traversed, it is evident that isobaric charts, showing the mean pressure of the atmosphere, form the key to the climates of the different regions of the globe, particularly those different climates which are found to prevail in different regions having practically the same latitude and elevation. ”

“ The upper layers of the atmosphere are much colder than the freezing-point of water. In the condensation which takes place there, the clouds do not resolve themselves into rain. The vapor of the up-streaming currents of warm air from the earth’s surface is condensed and frozen in these high regions, and passes into little crystals, which unite into flakes of snow. Even in summer the fine white cloudlets which you see floating at great heights are probably formed of snow. ”

“ The experience of balloonists and of mountain-climbers teaches us that snow forms and falls in all seasons of the year. This is melted by the warmed lower strata of air, and the earth thus saved from its chilling influence. ”

“ In a word, snow is water which has lost its latent heat, or—in a negative sense—has absorbed cold from the upper atmosphere. The falling snow conveys this chill to the earth, and thus acts as a great refrigerating agent. To overcome the cold thus conveyed from mid-air to the earth heat is necessary, and large supplies, which might have been usefully employed in the service of man, are lost in the conversion of vapor into snow, and thus indirectly consumed in warming the upper air. ”

“ When sufficient snow is added to the upper part of the glacier to cause the ice at the front to move forward equal to the rate at which it melts away, the glacier is in equilibrium with the climate. When the yearly added snow decreases in amount the ice front seems to retreat or move back, whereas the mass of the glacier is merely decreasing by melting on top and along the edges, just as a cube of ice left in the kitchen sink decreases in size. ”

“ Glacier ice is formed by snow accumulating at a given point more rapidly than it melts. This is due chiefly to wind, snow [Pg 353] slides, and heavy snowfall. The glacier, heavy and powerful, planes, polishes, and reshapes the surface over which it travels, or the walls with which it comes in contact. Most of the lake-basins were gouged out by glaciers. Mountain-ranges have been worn down to hills or plains; cañons and depressions have been filled, and extensive areas overlaid with ground-up rocky material. The gentle snowflake has been the earth's chief maker of scenery and soil. ”

“ Glaciers are accumulations of ice, descending by gravity combined with other forces and conditions, down mountain slopes, along valleys, from snow-covered elevations. They are streams or rivers of ice varying in depth from a few hundred to thousands of feet. They are fed by the snows and frozen mist of regions above the limits of perpetual snow. They stretch far below the limit of perpetual snow, because their masses are too thick to be melted by the heat of the summer. ”

“ The transformation is an interesting process, and the movement of the ice itself from the mountain to the sea is one of the strange mysteries of nature. With respect to the former, Professor Tyndall has stated the case so clearly that I can not refrain from quoting the following passage from his excellent work entitled “The Glaciers of the Alps:”
“Could our vision penetrate into the body of the glacier, we should find that the change from white to blue essentially consists in the gradual expulsion of the air which was originally entangled in the meshes of the fallen snow. ”

“ It is true that glaciers have ages, almost endless, in which [Pg 388] to do their work, but slowly as they move, their destination is the sea, where they must one day be swallowed up. Always immovable in appearance, they are really ice rivers flowing in a rocky bed. On its course the solid river behaves very much as would one of running water. It has its windings, its depths and shallows, its rapids and cascades.
A GLACIER AND CREVASSE.
But the ice, not possessing the suppleness or fluidity of water, accomplishes, somewhat awkwardly, the movements forced upon it by the nature of the ground. ”

“ Ice forms, and every particle of water is swollen by the change. A strain is put upon the mineral particles against which the particles of ice crowd for more room. Frost is a very powerful agent in the crumbling of rocks, as well as of stubborn clods of earth. In warm climates, and in desert regions where there is little moisture in the rocks, this destructive action of freezing water is not known. In cold countries, and in high altitudes, where the air is heavy with moisture, its greatest work is done. ”

“ Water beats upon the rocks of the sea-shore until it pounds them into sand, or rolls them into pebbles and boulders. It also sweeps the rich soil from the mountains into the valleys. In the form of snow it clothes the surface of the temperate and frigid zones with a warm mantle, which preserves vegetable life from the killing frosts of winter. In the form of ice it splits asunder the granite hills; and in the northern regions it forms great glaciers, or masses of solidified snow, many miles in extent, and many hundred feet thick. ”

“ Greenland and the Arctic regions hold all that remains of the glacial period in North America. Their shrunken ice-fields, formidable as they seem to us, are to the frozen masses of that secular winter but as the patches of snow and ice lingering on the north side of our hills after the spring has opened; let us expand them in imagination till they extend over half the continent, and we shall have a sufficiently vivid picture of this frozen world. ”

“ Need we wonder if at a time when the northern ice-sheet approached the fiftieth parallel of latitude in middle Europe, when almost every mountain-group of central and southern Europe had its snow-fields and glaciers—need we wonder if at such a time the climate of wide areas outside of the glaciated tracts was extremely ungenial? The more closely the superficial accumulations of such areas are studied, the more clearly do we perceive in them the evidence of cold and humid conditions. Try, then, to picture to yourselves the probable aspect of those regions during a glacial epoch. ”

“ There was a time, far in the past, but within the era of man's occupancy of the earth, when the influence of the snow was enormously greater than at present, and when the atmospheric chill, stored in the falling flakes, rendered a vast region of the northern continents unfit for human habitation, and extended the border of the frozen zone far toward the present limits of tropical heat. Doubtless if at present all the snow which forms in the upper air should reach the earth's surface, a glacial epoch would now exist in the north temperate zone. ”

“ So long as the lands of the globe were discontinuous and of relatively small extent, warm ocean-currents reaching polar regions produced a general uniformity of temperature—the climate of the terrestrial areas being more or less markedly insular in character. ”

“ During the times I spoke of last night, when the earth crust is breaking, the molten rock and gases and water vapor in the interior of the planet rise in the hearts of the mountain ranges, and often break through as active volcanoes, pouring their lava and ash over the underlying granite, and building it still higher.
“These heightened mountain ranges bring about the glacial climates. For the snows on their cold peaks do not melt when summer comes, and consequently they accumulate, and accumulate, till their own weight presses them down as hard as ice,—that is, makes glaciers of them. ”

“ But though the men who live on these mountains have thus made three countries out of them, the whole region is in nature one. It constitutes one mighty mass of mountainous land, which is lifted up so high into the air that all the summits rise into [Pg 14] the regions of intense and perpetual cold, and so condense continually, from the atmosphere, inexhaustible quantities of rain and snow. ”

“ Temperature of the Glacial Period.—Some geologists hold that the glacial phenomena were the result of warmer, not of colder, conditions of climate than now exist. Their views are briefly summarized by M. Millot, of the scientific faculty of Nancy, France. For the production of glaciers in temperate latitudes an active evaporation at the equator, to furnish moisture to be condensed into snow on the mountains, is above all things necessary. Thus, the quantity of ice produced will be within certain limits proportioned to the heat received at the equator. No heat, no evaporation ”

“ The great climatic regions of the earth, like the hot, wet equatorial belt or the warm, dry trade-wind belts or the cool, well-watered temperate zones, constitute, through the medium of their economic products and their climatically imposed methods of production, so many socio-political areas, regardless of ethnic and political boundaries. ”

“ Pushing away from the congenial temperatures of equatorial and temperate regions, life ventures into the inhospitable frozen zones of the polar regions, and by adaptation to such clime invades the most forbidding sphere. Earth's 'warm embrace' is here a 'cold reception,' but hosts of birds, mammals, fishes and insects have become established and would doubtless suffer extinction in other apparently more congenial regions. ”