Changes in the Oceanic Circulation and Their Climatic Consequences

Abstract

I N the last decade of the nineteenth century, between I892 and i 897, there occurred an enormous outburst of ice from the Antarctic which filled the Southern Ocean with ice floes and icebergs to such an extent that traffic between South America, Africa, and Australia had to seek a more northerly track. This outburst had far-reaching climatic repercussions. The monsoon regimen of the Indian Ocean was profoundly disturbed. In India I893 and I894 were years of excessive rainfall; then, in I896 and I899, came years of drought followed by widespread famine. The area in which crops failed more or less completely was about 256,ooo square miles in extent in I896 and 500,000 square miles in I899. In I899-I900 upwards of 6,500,000 people were on famine relief for several months. The loss of cattle was great, running into many millions: in some districts 90 to 95 per cent of the stock died. Australia also suffered. In New South Wales and Queensland almost continuous drought prevailed from I896 to I902. It is estimated that over 50,000,000 sheep, valued at ?I2,500,000, were lost during these seven years.' Reports of ice dangerous to navigation in the Southern Ocean began to appear again in I922. We do not know which part of the Antarctic shelf was the original seat of this outburst, but it seems likely that it came from the Pacific and Atlantic rather than from the Indian side since its aftereffect has been a disturbance of the Humboldt and the Benguella currents. On the former current Mr. R. C. Murphy has published an elaborate and comprehensive study.2 He shows that the Humboldt Current must have been deflected westwards early in I925, allowing the warm coastal waters from the Bay of Panama, i.e. the countercurrent El Nifio, to penetrate southwards along the coast and thus cause an abnormal rainfall along the arid coasts of Ecuador, Peru, and Chile. This phenomenon though rare is not unprecedented; it appears to repeat itself periodically at intervals of about 34 years, which reminds one of the Bruckner cycle.