What with all the immensity of space in the South Pacific, we should expect to find here the most powerfully impressive of all ocean currents, but this does not seem to be true. The South Equatorial Current has its course so frequently interrupted by islands, which are forever deflecting streams of its water into the central basin, that by the time it approaches Asia it is, during most seasons, a comparatively feeble current, lost in a confused and ill-defined pattern around the East Indies and Australia.[24] The West Wind Drift or Antarctic Current—the poleward arc of the spiral—is born of the strongest winds in the world, roaring across stretches of ocean almost unbroken by land. The details of this, as of most of the currents of the South Pacific, are but imperfectly known. Only one has been thoroughly studied—the Humboldt—and this has so direct an effect on human affairs that it overshadows all others.
The Humboldt Current, sometimes called the Peru, flows northward along the west coast of South America, carrying waters almost as cold as the Antarctic from which it comes. But its chill is actually that of the deep ocean, for the current is reinforced by almost continuous upwelling from lower oceanic layers. It is because of the Humboldt that penguins live almost under the equator, on the Galapagos Islands. In these cold waters, rich in minerals, there is an abundance of sea life perhaps unparalleled anywhere else in the world. The direct harvesters of this sea life are not men, but millions of sea birds. From the sun-baked accumulations of guano that whiten the coastal cliffs and islands, the South Americans obtain, at second hand, the wealth of the Humboldt Current.
Robert E. Coker, who studied the Peruvian guano industry at the request of that government, gives a vivid picture of the life of the Humboldt. He writes of
…immense schools of small fishes, the anchobetas, which are followed by numbers of bonitos and other fishes and by sea lions, while at the same time they are preyed upon by the flocks of cormorants, pelicans, gannets, and other abundant sea birds… The long files of pelicans, the low-moving black clouds of cormorants, or the rainstorms of plunging gannets probably cannot be equaled in any other part of the world. The birds feed chiefly, almost exclusively, upon the anchobetas. The anchobeta, then, is not only… the food of the larger fishes, but, as the food of the birds, it is the source from which is derived each year probably a score of thousands of tons of high-grade bird guano.[25]
Dr. Coker estimated the annual consumption of fish by the guano-producing birds of Peru as equal to a fourth of the total production of all United States fisheries. Because of this diet, which links the birds with all the minerals of the sea, their excrement is the most valuable and efficient fertilizer in the world.
Leaving the coast of South America at about the latitude of Cape Blanco, the Humboldt Current turns westward into the Pacific, carrying its cool waters almost to the equator. About the Galapagos Islands it gives rise to a strange mixture of waters—the cool green of the Humboldt and the blue equatorial waters meeting in rips and foam lines, suggesting hidden movements and conflicts deep in the sea.
The conflict between opposing water masses may, in places, be one of the most dramatic of the ocean’s phenomena. Superficial hissings and sighings, the striping of the surface waters with lines of froth, a confused turbulence and boiling, and even sounds like distant breakers accompany the displacement of the surface layers by deep water. As visible evidence of the upward movement of the water masses, some of the creatures that inhabit the deeper places of the sea may be carried up bodily into the surface, there to set off orgies of devouring and being devoured such as Robert Cushman Murphy witnessed one night off the coast of Colombia from the schooner Askoy. The night had been still and dark, but the behavior of the surface made it clear that deep water was rising and that some sort of conflict was in progress among opposing water masses far below the ship. All about the schooner small, steep waves leaped into being and dissolved in foaming whitecaps, pricked with the blue fire of luminescent organisms. Suddenly,
On either side, and at a bafflingly uncertain distance from the ship, a dark line, like a wall of advancing water, seemed to be closing in upon us… We could hear the splash and murmur of a troubled surface close by… Presently we could see a gleam of foam sprinkled with points of luminescence on the slowly approaching swell or head to the left. Vague and unfounded thoughts of marine earthquake bores occurred to Fallon and me together, and we felt peculiarly helpless with a dismantled engine and no breeze to make the craft answer her helm. The dreamlike slowness of all that was going on, moreover, gave me a feeling that I had not yet fully shaken off the bonds of three hours’ slumber.
However, when the dark, white-outlined menace, reached us, it proved to be nothing more than a field of the dancing water, tossing its little peaks a mere foot or so into the air and beating a tattoo on the steel flanks of ‘Askoy’…
Presently a sharp hissing sound, different in character from the bursting of small waves, came out of the darkness to starboard, and this was followed by strange sighings and puffings… The puffers were blackfish, many scores, or perhaps hundreds of them, rolling and lumbering along and diving to pass beneath ‘Askoy’ shortly before they reached her bilge… We could hear the bacchanalian clamor of their rumblings and belchings. In the long beam of the searchlight, the hissing proved to come from the jumping of small fishes. In all directions as far as the light carried, they were shooting into the air and pouring down like hail…
The surface was seething, boiling with life, much of which was de profundis. Larvae of clawless lobsters, tinted jellyfish, nurse chains of salpa, small herringlike fishes, a silvery hatchetfish with its face bitten off, rudder fishes, hanging head downward, luminous lantern-fishes with shining light pores, red and purple swimming crabs, other creatures which we could not name at sight and much that was too small even to see distinctly…
A general holocaust was in progress. The little fishes were eating invertebrates or straining out the plankton; the squids were pursuing and capturing fish of various sizes; and the blackfish were no doubt enjoying the squids…
As the night wore on, the amazing manifestations of abundance and devouring gradually, almost imperceptibly, died away. Eventually, ‘Askoy’ lay once more in water that seemed as still and dead as oil, and the lap-lap of skipping waves drew off farther and farther into the distance until it was lost.[26]
Although such exciting displays of upwelling are seen and recognized by comparatively few people, the process takes place regularly off a number of coasts and at many places in the open ocean. Wherever it occurs, it is responsible for a profusion of life. Some of the world’s largest fisheries are dependent on upwelling. The coast of Algeria is famous for its sardine fisheries; the sardines are abundant here because upward streams of deep, cold water provide the minerals to support astronomical numbers of diatoms. The west coast of Morocco, the area opposite the Canary and Cape Verde islands, and the southwest coast of Africa are other sites of extensive upwelling and consequent richness of marine life. There is an amazingly abundant fish fauna in the Arabian Sea near Oman and on the Somali Coast near Cape Hafun, both occurring in areas of cold water rising from the depths. In the South Equatorial Current north of Ascension Island is a ‘tongue of cold’ produced by the rise of sea water from the bottom. It is extraordinarily rich in plankton. Upwelling around the island of South Georgia, east of Cape Horn, makes this one of the world’s centers of whaling. On the west coast of the United States the catch of sardines is sometimes as much as a billion pounds in a year, supporting one of the largest fisheries in the world. The fishery could not exist except for upwelling, which sets off the old, familiar biological chain: salts, diatoms, copepods, herring. Down along the west coast of South America, the astonishing profusion of life in the Humboldt is maintained by upwelling, which not only keeps the waters of the current cold in all its 2500-mile course to the Galapagos Islands but brings up the nutrient salts from the deeper layers.
24
One of the most exciting recent events in oceanography was the discovery of a powerful current running under the South Equatorial current but in the opposite direction. The core of the counter current lies about 300 feet below the surface (although shallower near its eastern terminal in the vicinity of the Galapagos Islands). This subsurface current is about 250 miles wide and it flows at least 3500 miles eastward along the equator at a speed of about 3 knots. (The speed of the surface current is only about one knot.) The existence of the current was discovered in 1952 by Townsend Cromwell in the course of a U.S. Fish and Wildlife Service investigation of methods of tuna fishing. Cromwell observed that long lines set for tuna at the equator did not move westward with the surface current, as would be expected, but drifted rapidly in the opposite direction. It was not until 1958, however, that an extensive survey of the current was made by the Scripps Institution of Oceanography and its impressive dimensions measured. This same survey gave further proof that the deep circulation of the ocean is far more complicated than has generally been realized, for beneath the swift-flowing eastward current was still another, flowing to the west. In only the uppermost half mile of Pacific equatorial waters, therefore, there are three great rivers of water, one above the other, each flowing on its own course independent of the other. When such surveys can be extended all the way to the floor of the ocean an even more complex picture will undoubtedly be revealed.
Only a year before the detailed charting of this Pacific current, British and American oceanographers discovered a south-flowing counter current running from the North to the South Atlantic under the Gulf Stream and the Brazil Current. The techniques that make such discoveries possible have only very recently become available to oceanographers. As their use becomes more widespread our almost complete ignorance of the deep circulation of the ocean will be dispelled.