Tropical ocean

“ The ocean is also the great source of moisture, and this, too, it distributes over the land through the agency of the wind. Where warm ocean currents, like the Gulf Stream and Kuro Siwa, penetrate into temperate or sub-polar latitudes, or where cool ones, like the Peruvian and Benguela Currents wash the coasts of tropical regions, they enhance the power of the ocean and wind to mitigate the extremes of temperature on land. ”

“ Now, under the continuous blazing sun of the torrid zone the sea-water near the surface gets fairly warm,—having an average temperature of about 85° along the equator,—while in the polar regions the ocean is always chilled by permanent or floating ice until it is nearly cold enough to freeze; but these masses of warm and cold water cannot remain separate in the universal ocean. The hot tropical flood, continually rising, must flow away somewhere to find its level ”

“ Wholly overcast, dull days, such as are common in the winter of the temperate zone, occur frequently only on tropical coasts in the vicinity of cold ocean currents, as on the coast of Peru and on parts of the west coast of Africa. ”

“ Within a few yards of the surrounding glaciers, and close to the sea, the vegetation is abundant, and in many places semi-tropical, a fact which is due to the comparatively mild winters, the temperate summers, the moist climate, and the rich soil of these parts. Passing up English Reach, we now caught our first glimpse of the Pacific Ocean, between Cape Pillar on one Page 139side, and Westminster Hall, Shell Bay, and Lecky Point, on the other. ”

“ PAGE 112 THE PHYSICAL GEOGRAPHY OF THE SEA.
and continues on toward the coast of South America, in the same direction, appearing now as the prevailing northwest wind of the extra-tropical regions of the southern hemisphere. Traveling on the surface from warmer to colder regions, it must, in this part of its circuit, precipitate more than it evaporates.
202. Now it is a coincidence, at least, that this is the route by which, on account of the land in the northern hemisphere, the northeast trade-winds have the fairest sweep over that ocean. ”

“ There is something in a tropical forest akin to the ocean in its effects on the mind. Man feels so completely his insignificance there, and the vastness of nature. ”

“ Probably it reaches the surface and exerts an influence, also, upon the weather through the ocean, and by heating it in its greatest depths. Little attention has been paid, so far as I am informed, to the question how far the ocean is thus heated in tropical latitudes. Doubtless a portion of the warmth of the ocean there is derived from that source, and it has its influence in changing the temperature of the [Pg 10] deep-seated cold polar currents of, the great oceans. Perhaps it may yet be found that the icebergs are detached by it in the polar seas—the observations of Dr. ”

“ OUR story opens in that broad, far-reaching expanse of water which lies deep and blue between the two hemispheres, some fifteen degrees north of the equator, in the latitude of Cuba and the Cape Verd Islands. The delightful trade winds had not fanned the sea on a finer summer's day for a twelvemonth, and the waves were daintily swelling upon the heaving bosom of the deep, as though indicating the respiration of the ocean. ”

“ Meeting no land in this long oblique track over the tepid waters of a tropical sea, it would, if such were its route, arrive somewhere about the meridian of 140° or 150° west, at the belt of equatorial calms, which always divides the north-east from the south-east trade-winds. Here, depositing a portion of its vapour as it ascends, it would, with the residuum, take, on account of diurnal rotation, a course in the upper region of the atmosphere to the south-east, as far as the calms of Capricorn. ”

“ The air currents come up over the valleys, plateaus, hills and mountain sides, fresh from the ocean currents that wash the Pacific shores. These ocean streams are heated under an equatorial sun and sweeping north around the circle of the earth, temper the whole western slope. ”

“ The warmer the atmosphere, the greater its capacity to hold moisture. The heated, thirsty air of the tropics drinks up the water of the ocean, and bears it away to the colder regions, where, through condensation by cold, it becomes visible as a cloud ”

“ It has been tacitly assumed that all marine organisms coming from regions bordering the equator must have lived under tropical conditions; but deep-sea research has shown that all conditions of temperature and of light prevail at their several depths in tropical as well as other seas ”

“ The consequence is that the air over the interior of the continent becomes more rare than over the oceans, rises up and flows out in all directions above while the barometric pressure is diminished, and the air from all sides, from the Atlantic on the east to Pacific Ocean on the west, the Gulf of Mexico on the south, and the polar sea on the north, flows in below to supply its place. ”

“ Remote alike on one side from the moderating tropical rains, on the other from the equalizing influences of the sea, destitute of high mountain chains and extensive forests to draw down and retain moisture, the whole expanse is virtually a naked plain, basking under a semitropical sun. ”

“ Pursuing the study of the climates of the sea, let us now turn to Plate VI. Here we see at a glance how the cold waters, as they come down from the Arctic Ocean through Davis’s Straits, press upon the warm waters of the Gulf Stream, and curve their channel into a horse-shoe. ”

“ If a storm arises, the whole creation seems to be dissolving. No words can be found adequate to describe the scene, or in any measure to convey the frightful experience the sailor has to undergo. But on the other hand, in clear and calm weather, the tropical sea 171 presents an aspect of gorgeousness and grandeur, with which the loveliest natural scenery of a northern climate cannot compare. ”

“ Mildly they reply, as they gently fan us, "we will sweep the broad ocean, tempering the burning heat of the tropic sun to the half-fainting voyager as he passes through the torrid zone, and, bearing aloft the ocean-spray to the clouds, convey it as refreshing dew to the arid soil of Africa, and to the islands and mainland of Europe to saturate the ground in preparation for forthcoming fruits and flowers." ”

“ The whole system of trade-winds, equatorial and tropical calms, with the cloud ring, follow the sun in declination; consequently in its journeys back and forwards it annually travels over 1000 miles of latitude, and regulates the dry and rainy season in the tropical parts of the earth. ”

“ Continental surfaces are known to be productive of extremes of temperature, while the climate of sea areas is comparatively equable; and the general character of the climate of land and water surfaces is further and locally affected by the configuration and altitude of the land, by the breadth and depth of the oceanic basins, and especially by the ocean-currents. The sea forms the great evaporating surface, and the source from which is derived the enormous quantity of water transported by the system of atmospheric circulation. ”

“ And fully to understand this pregnant educational importance of the Tropics we must consider with ourselves how large a part tropical conditions have borne in the development of life in general, and of human life and society in particular.
The Tropics, we must carefully remember, are the norma of nature: the way things mostly are and always have been. They represent to us the common condition of the whole world during by far the greater part of its entire existence. ”

“ They gradually pass into warm; for in traveling from the poles to the equator they partake of the temperature of the latitudes through which they flow, and grow warm.
535. Plate IX., therefore, is only introduced to give general ideas; nevertheless, it is very instructive. See how the influx of cold water into the South Atlantic appears to divide the warm water, and squeeze it out at the sides, along the coasts of South Africa and Brazil. So, too, in the North Indian Ocean, the cold water again compelling the warm to escape along the land at the sides, as well as occasionally in the middle. ”

“ The dark, sombre green of the tropic landscape stretches for miles and miles. There lies the expanse of the sapphire-hued ocean, ending far away in the pale saffron fires of the skyline’s sunset, as, in my imagination, I softly dip my pen into the magic foams that sparkle on the coral-dust sands at my feet and sigh with the coco-palms overhead. ”

“ Between the tropics there is a sight haziness, like a thin gauze, drawn over the sun, which, without obstructing or obscuring the light, tempers the heat which comes down with perpendicular fierceness in the Atlantic and Indian tropics. ”

“ The result is that before it begins to ascend in the tropical updraught, being much moisture-laden, the atmosphere stores a good deal of heat. As it rises, rarefies, and cools, the moisture descends in the torrential rains which ordinarily fall when the sun is nearly vertical in the tropical belt. ”

“ And thus on it goes, round and round the world; down in the ocean's depths, up in the cloudy sky, deep in the springs of earth; ever moving, ever active, never lost, and always fufilling the end for which it was created.
All ocean currents are composed of water in one or other of the conditions just described;—the hot and salt waters of the equator, flowing north to be cooled and freshened; the cold and fresh waters of the north, flowing south to be heated and salted. The Gulf Stream is simply the stream of equatorial hot water that flows towards the pole through the Atlantic. ”

“ It has already been shown that, although marshes and rivers, inland seas and lakes, yield by evaporation watery vapours to the air, the ocean is the great source of rain, whence it is lifted in vast quantities by the sun’s radiant heat, to be subsequently condensed by passing into cooler regions, or by contact with cold mountain peaks, falling to earth as a fertilizing shower or a devastating flood. ”

“ A person who has never been in the South Seas cannot appreciate the pleasure of gliding along a tropical bay, just close enough to see the small grass villages and the dense jungles behind; the seas breaking over the coral reefs ahead, and the pure blue waters underneath; the tropical birds flying overhead, and canoes paddling along the shores. ”

“ Vessels navigating the Archipelago [Pg 41] between China and New Zealand, should make observations every three hours, in order that the undulations arising from the configuration of the terrestrial and oceanic surfaces may be more distinctly marked and more advantageously compared with the Gulf of Mexico, the Caribbean Sea, and the northern portion of the African continent.
The Pacific Ocean.—As this ocean presents so vast an aqueous surface, generally speaking observations at intervals of six hours will be amply sufficient to ascertain its leading barometric phænomena. ”

“ Though I speak of the ocean being calm, there was always a perceptible swell, more perceptible when we were on the weather-side of a coral reef, against which the swell, finding an impediment to its progress, could be seen dashing with tremendous force, rising high in the air in masses of foam. ”

“ Rocks and islands are adorned with the luxuriant vegetation of the tropical forest; a perpetual mist hovers over the waters, and the summits of the lofty palms pierce through the cloud of spray and vapour. ”

“ The winds, and the clouds now take charge of the new island, or continent, and begin to prepare it for vegetation, and the habitation of man, and animals. The Pacific Ocean, within the tropics is, par excellence, the coral sea, and the navigator of that ocean is familiar with the phenomenon, which I am about to describe. In the midst of a clear sky, the mariner sometimes discovers on the verge of the horizon, a light, fleecy cloud, and as he sails toward it, he is surprised to find that it scarcely alters its [Pg 172] position. ”

“ The trade winds prevail about thirty degrees on each side of the equator. This part of the ocean may be called the Elysian Fields of Neptune’s empire; and the torrid zone, notwithstanding Ovid’s remark, “non est habitabilis æstu,” is rendered healthy and pleasant by these gently-blowing breezes. The ship glides smoothly on, and you soon find yourself within the northern tropic. ”