The Coming Ice Age

by C. A. M. Taber

The Agulhas stream, which even now assists in replenishing the South Atlantic with tropical water, would, during the perfection of a glacial period, with the Cape channel closed, be a much stronger stream than it now obtains with the Cape channel possessing its present enlarged capacity, for the reason that the South Atlantic waters would continue as now to be forced eastward by the westerly winds, while they could not be replenished, as they are to-day, directly from the South Pacific.

Consequently, the waters of the South Atlantic Ocean would be correspondingly reduced.

Such conditions alone would greatly increase the volume of the Agulhas stream at the culmination of a frigid age. Therefore, the work of subduing a frigid period in the southern hemisphere after the Cape Horn channel was closed would not rest on the Brazil current alone, but also on the great equatorial stream of the Pacific and Indian Oceans.

Yet during such frigid times the sources of the equatorial stream would be greatly chilled by its two great feeders, the Humboldt current and the returning Japanese current, both of which flow down from the high latitudes and meet in the equatorial latitudes on the eastern side of the Pacific, thus cooling the source of the great equatorial current.

But this latter stream, while on its long western passage across the Pacific and Indian Oceans, beneath a torrid sun, with only one cold feeder from the south which approaches it along the west side of Australia, would, on its long tropical journey, be able to obtain considerable warmth, even during an ice period, to supply the Mozambique and Agulhas streams, and so greatly assist the Atlantic waters in bringing about a mild period. Still, the process of subduing the cold of the southern latitudes would be slow, even with the Cape Horn channel closed, because of the vast collection of ice burdening the sea and land.

Yet there were conditions that were naturally brought about to favor the process of returning warmth; for it appears that, when the southern ocean was made shallow because of a considerable portion of its waters having been moved into the northern hemisphere, it will be seen that the conditions were more favorable for the westerly winds to create drift currents than would be the case on deeper seas. Therefore, the high and low sea-levels caused by such winds would be greater on a shallow ocean than would occur on deeper waters. Thus the low sea-levels of the shallow southern sea would have strong attraction for tropical surface waters, and so increase the thickness of its warm drift currents, and at the same time its lessened depths would have less capacity for the storage of cold water to reduce the temperature of the under-waters of the tropical zone.

And, furthermore, when the southern ocean was shallow, New Zealand acquired a longer extension of land to the north and south. Consequently, the enlarged low sea-level on its eastern side attracted more tropical water into the southern latitudes than now.

So, according to the conditions I have pointed out, the ice-sheets would at length melt away, and a long period of mildness would succeed on account of the length of time it would require after the ice disappeared from the earth for the prevailing winds to move the surface waters of the augmented northern seas into the southern ocean, and again restore its independent circulation, and so, after a considerable lapse of time, bring about the geographical and climatic conditions existing at the present date, which can be seen on [map No. 2], which shows that a cold period has already made considerable advance in the southern hemisphere, the southern continent and islands being covered with glaciers, and the prevalence of icebergs as far north as the latitude of 35° south.

Moreover, when we consider that the independent circulation of the southern ocean is caused by the westerly winds blowing its surface waters constantly around the globe through the open Cape Horn channel, and so largely preventing the tropical currents from entering the high southern latitudes, and how, in consequence, the cold is slowly on the increase through the constant accumulation of ice on the lands and in seas of the southern latitudes, it appears that a frigid age is slowly progressing in the southern hemisphere. For it seems that continental ice-sheets should not only be able to retain their freezing temperature, but also the mean of the low temperature in which they were formed, for a considerable length of time, and so impart their extreme coldness in the shape of icebergs into such seas as border on the glaciated lands.

It has been proved at Point Barrow that strata of ice and gravel can maintain a wintry temperature through the summer months. Captain G. B. Borden, keeper of the refuge station in that region, states that Lieutenant Ray, of the Signal Service, excavated through ice and gravel to a depth of forty-one feet, and that the lower portion of the excavation maintains a temperature 15° Fahrenheit above zero the year around. Therefore, with the probability of southern glaciers obtaining a temperature of over 15° Fahrenheit below the freezing point, we can well realize the frigidity imparted to the southern oceans while melting numerous immense icebergs, and consequently will conclude that the temperature of the southern latitudes is gradually lowering.