Oceanography

“ In dynamic oceanography the ocean is studied in motion. We study the waves, which move the surface under the influence of the wind, and the currents, which, like the network of our arteries and veins, traverse its mass to a certain depth, and result from the simultaneous actions of heat, evaporation, the topography of the sea bottom, the geographic configuration of the surrounding continents, the climate, the force of the winds ”

“ Like geography, oceanography may be viewed in two different ways, and is conveniently divided into general oceanography, which deals with phenomena common to the whole ocean, and special oceanography, which has to do with the individual characteristics of the various divisions of the ocean. ”

“ The line between these various branches of science is for our present purpose difficult to draw; but at the risk of a charge of arbitrary treatment it appears pertinent to refer to certain facts in the history of oceanography. As an organized department this is no less a creation of the nineteenth century than others we have named. Among ancient geographers there was certainly some speculation as to the physical character of the seas, known and unknown. ”

“ Thus geology, meteorology, oceanography and anthropology developed into distinct sciences. The absurd attempt was, and sometimes is still, made by geographers to include all natural science in geography; but it is more common for specialists in the various detailed sciences to think, and sometimes to assert, that the ground of physical geography is now fully occupied by these sciences. ”

“ As commerce extended, such observations became more full, and resulted in systematic coast-surveys in which the depth of water, currents, magnetic conditions, temperatures, tides, and winds, were taken into account, and the knowledge thus accumulated gave rise at length to a great science—the Physical Geography of the Sea. About twenty-five years ago a new step was taken toward the extension of our knowledge of sea-depths. Science had given to the world the electric telegraph, and commerce demanded that it should be laid across the ocean. ”

“ The water of the earth's surface, viewed from the standpoint of anthropo-geography, is one, whether it appears as atmospheric moisture, spring, river, lake, brackish lagoon, enclosed sea-basin or open ocean. Its universal circulation, from the falling of the dews to the vast sweep of ocean current, causes this inviolable unity. Variations in the geographical forms of water are superficial and constantly changing; they pass into one another by almost imperceptible gradations, shift their unstable outlines at the bidding of the mobile, restless element. ”

“ Besides the intricate labyrinth of islands, reefs, rocks, and shoals which are scattered over its surface, there are recorded the variations of the compass, the directions of the ocean currents, and the results of countless soundings. Running your pencil through all the points on this map for which the indicated depth is fifteen hundred fathoms or thereabouts, you will be able to trace out an irregular and more or less interrupted band, extending from the East Indian seas nearly to the coast of South America. Within the area thus marked out the sea is comparatively shallow ”

“ Seeing, then, that the inhabitants of the sea, with their powers of secretion, are competent to exercise at least some degree of influence in disturbing equilibrium, are not these creatures entitled to be regarded as agents which have their offices to perform in the system of oceanic circulation, and do they not belong to its physical geography? Their influences upon the economy of the sea are like those outstanding quantities which the astronomer finds in the periods of heavenly bodies. ”

“ 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. ”

“ The Pacific and Atlantic, though both depressions or flattenings « 59 » of the earth, are, as we shall find, different in age, character, and conditions; and the Atlantic, though the smaller, is the older, and, from the geological point of view, in some respects, the more important of the two; while, by virtue of its lower borders and gentler slope, it is, though the smaller basin, the recipient of the greater rivers, and of a proportionately great amount of the drainage of the land. [22]
[21] Dana, "Manual of Geology," introductory part. ”

“ The geological clock may, we thought, strike new periods; its hands may point to era after era; but, so long as the ocean remains in its basin, so long as its bottom is covered with blue water, so long must the deep furrows and strong contrasts in the solid crust below stand out bold, ragged, and grand. Nothing can fill up the hollows there; no agent now at work, that we know of, can descend into its depths, and level off the floors of the sea. ”

“ It was, however, impossible to invent any satisfactory hypothesis to explain the disappearance of so enormous a body of water throughout the globe, it being necessary to infer that the ocean had once stood at whatever height marine shells might be detected. It moreover appeared clear, as the science of Geology advanced, that certain spaces on the globe had been alternately sea, then land, then estuary, then sea again, and, lastly, once more habitable land, having remained in each of these states for considerable periods. ”

“ Doubtless it is given to the winds, that they may bear it off to distant regions, and make lands fruitful, that but for these sources of supply would be almost rainless, if not entirely arid, waste, and barren. These seas and arms of the ocean now present themselves to the mind as counterpoises in the great hygrometrical machinery of our planet.—As sheets of water placed where they are to balance the land in the trade-wind region of South America and South Africa, they now present themselves. ”

“ That the fauna of the ocean, apart from the influence of temperature, would be much more uniform, and therefore less susceptible of being divided into zoological provinces, or regions, will be apparent from a glance at the map of the world on Mercator's projection, in which the fact that the three great oceans the Pacific, the Atlantic and the Indian are in free communication with one another in the southern hemisphere is clearly brought out. ”

“ Shore Deposits and Stratified Rocks.—If we go round the shores of any of our continents we shall almost always find a considerable belt of shallow water, meaning thereby water from 100 to 150 fathoms deep. The distance from the coast line at which such depths are reached is seldom less than twenty miles, and is very frequently more than a hundred, while in some cases such shallow seas extend several hundred miles from existing continents. The great depth of a thousand fathoms is often reached at thirty miles from shore, but more frequently at about sixty or a hundred miles. ”

“ All recent observations, he said, have shown that the vast expanse of water which has its centre in the southern hemisphere is the one great ocean of the world, and the Atlantic with the Arctic Sea, and the North Pacific, are merely its northward-extending gulfs: any physical phenomena affecting obviously one portion of its area must be regarded as one-of an interdependent system of phenomena affecting the ocean as a whole. ”

“ When, therefore, we take into consideration the fact that, as a general rule, sea water is, with the exception above stated, everywhere and always the same, and that it can only be made so by being well shaken together, we find grounds on which to base the conjecture that the ocean has its system of circulation, which is well calculated to excite our admiration, for it is as wonderful as the circulation of the blood. ”

“ Where does the water come from to fill the underground lakes and reservoirs and keep the rivers constantly flowing? Geologists tell us that all the land surface of the earth was for vast ages under water; that the great oceans that now roll between the continents once covered them entirely, but after long ages mighty internal forces of the earth raised them above the ocean’s level. For a long time after the hills and mountains were raised above the surface of the ocean, where the valleys and prairies now are there were lakes and inland seas. ”

“ When ocean electric cables for connecting islands and continents are laid, engineers find that there are the same sort of plains, mountains, valleys, and gorges beneath as above the waters of the ocean. The skeletons of whales, and natural beds of deep-sea shells, found in valleys and hills many hundred feet above the present level of tide waters, tell us plainly enough that in the long ages which have passed, the diversified surface of the earth which we now behold has changed places with these submerged regions, which probably once formed the dry land. ”

“ As shown below, only a small part of the coast line of the world is thoroughly surveyed. In the extensive ocean areas which are dotted with islands or reefs, a large amount of work is required for their sufficient charting, although many doubtful areas have been cleared up in recent years. Even the parts that are known to be of depths so great as to be free from navigational dangers should be sounded over sufficiently to develop the general configuration of the ocean bottom. ”

“ The ocean, therefore, is the great depository of everything that water can dissolve and carry down from the surface of the continents; and, as there is no channel for their escape, they of course consequently accumulate. ”

“ The height to which the tides rise, and the violence and velocity of currents, depend in a great measure on the actual configuration of the land, the contour of a long line of continental or insular coast, the depth and breadth of channels, the peculiar form of the bottom of seas—in a word, on a combination of circumstances which are made to vary continually by many igneous and aqueous causes, and, amongst the rest, by the tides and currents themselves. ”

“ If latitude and longitude are not readily available, record best available position, for example 5 hours at 10 knots, SE of Miami.
[14] Any oceanographic or bathymetric information obtainable at the time of sighting may be significant. Such measurements as water depth, presence of large fish schools, or deep scattering layer/organisms (DSL) characteristics of the bottom (e.g., flat sand plain, sea mount, submarine cliff) , surface temperature, depth of thermocline, and salinity should be included if available. ”

“ The argument on both sides depends upon theories to which travellers can contribute but little except by observations on the geology, fauna, and flora of oceanic islands, and by the investigation of coral-reefs and especially of atolls. In ranges of hills or mountains near the coast both of continents and islands and in all tracts where evidence of recent elevation exists, search should be made for deep-sea deposits. ”

“ What should make the waters of the Mexican Gulf and Caribbean Sea salter than the waters in those parts of the ocean through which the Gulf Stream flows? There are physical agents that are known to be at work in different parts of the ocean, the tendency of which is to make the waters in one part of the ocean Salter and heavier, and in another part lighter and less salt than the average of sea-water. These agents are those employed by sea-shells in secreting solid matter for their structures ”

“ PAGE 149 THE OPEN SEA IN THE ARCTIC OCEAN.
surface, by changes, from whatever cause, in the course or velocity of the surface current, for obviously the under current could not bring more water into the frozen ocean than the surface current would carry out again, either as ice or water.
287. Every winter, an example of how very close warm water in the sea and a very severe climate on the land or the ice may be to each other, is afforded to us in the case of the Gulf Stream, and the Labrador-like climate of New England, Nova Scotia, and Newfoundland. ”

“ Those slow alternations of elevation and subsidence which take place over immense areas, here producing a continent where once there was a fathomless ocean, and there causing wide seas to spread where in a long past epoch there stood snow-capped mountains, gradually work great atmospheric changes. While the highest parts of an emerging surface of the Earth's crust exist as a cluster of islands, the plants and animals which in course of time migrate to them have climates that are peculiar to small tracts of land surrounded by large tracts of water. ”

“ Upon the sides of mountains, or on their summits, now thousands of feet above the level of the ocean, unquestionable traces of the action of the sea can be found. And the scientific observer of to-day sees all about him evidences that the immense work of the creation of continents, commenced by the sea in the earliest periods of time, is to-day continuing without relaxation or intermission, and with such energy that even during the short course of a single life great changes can be seen to have been produced. ”

“ Here, too, our knowledge is exceedingly imperfect, though the blanks upon the geological map of the world are yearly diminishing in extent. Lastly, as a most valuable supplement to geology, we require to know approximately, the depth and contour of the ocean-bed, since this affords an important clue to the former existence of now-submerged lands, uniting islands to continents, or affording intermediate stations which have aided the migrations of many organisms. ”