The diverse Ocean environment is a system of complex unions and interactions between the atmosphere, water, bottom and their inhabitants. As a whole, they form the unique character of the Ocean, in which many features are still insufficiently investigated. The influence of the Ocean has an effect in the most remote corners of the Earth. The lack of knowledge of the Ocean environment therefore, presents a real problem for modern science.
 
 

The area of the Earth surface is equal to 510,100,000 km². Land covers 148,800,000 km² (29.2%) and the World Ocean covers 361,300,000 km² (70.8%). The World Ocean is a continuous water “blanket” over the Earth adjacent to all of the continents and islands and possesses a generally salty structure.

In the Northern Hemisphere, the World Ocean occupies 61% of the area and in the Southern Hemisphere, 81%. If we were able to arbitrarily divide the Globe into two equal parts so that in one hemisphere the land predominated, and in the other the water, water will appear to cover more than half of the area (53%). The oceanic hemisphere takes up about takes 91% of the area. The land and sea are also non-uniformly distributed on the planet. Land predominates only between latitudes of 45° N and 70° N, and to the south, from latitude 70° S to the South Pole. Water predominates over the remaining part of Globe. The shapes of the shorelines, bottom relief, systems of oceanic currents, tides, atmospheric circulation and a number of other criteria subdivide the World Ocean into the Pacific, Atlantic, Indian and Arctic Oceans.

With the broadening of knowledge about Antarctic waters as a unified, physical-geographical area, some scientists now separate the waters surrounding the Antarctic continent, an area of 86 million km², into a different water body: the Southern Ocean. Although widely used in scientific and other literature, the term “Southern Ocean” has not yet received official status.
 
 

On the surface of the Earth, altitudes less than 1,000 m and depths from 3,000 up to 6,000 m predominate. It is shown on a hypsographic profile constructed from the areas derived from various kinds of charts, showing the heights of the land and the depths of the Ocean over the entire planet.

1. Sea level 2. Continental shelf 3. Continental slope 4. The Ocean floor  5. Mean depth of the World Ocean 3711m  6. Mean altitude of the land 840m 7. Jomolungma 8848m 8. Marianas Trench 11022m

The water cover of the Earth (called the “Hydrosphere”) has volume of 1,389,500,000 million km², and 97.4% consists of salt water. Of this volume, 96.5% is in the World Ocean, and 0.9% is in salty underground and lake waters.

Fresh water comprises only 2.6% of the total volume of the Hydrosphere. This is the water contained in the atmosphere, rivers, lakes, glaciers, underground and ground water, and also the waters contained internally in animals and plants.

The waters of the World Ocean are distinguished from fresh water by their differing physical and chemical properties. By well-defined differences and a complex exchange of energy and matter peculiar to the animal and plant kingdoms, a subclass of the Hydrosphere exists, called the “Oceanosphere”, can be separated from the rest of the hydrosphere. The Oceanosphere has a great influence on the formation and changes of the natural world.

The World Ocean (Oceanosphere) contains on the order of 1,340.7 million km³ of water, making up 1/800^th of the total volume of the Earth (1,083.3 billion km³). Alternatively, the volume of fresh water is about 35.8 million km³. If the Oceanosphere was shown in the form of a sphere, its radius would be equal to 690 km, or 0.11 mean radii of the Earth (6,371 km).

In the process of exchanging water with the atmosphere and continents, World Ocean annually produces atmospheric precipitation of about 458,000 km³; both rivers and ground water produce about 48,000 km³ of water. Evaporation from the surface of the Ocean produces 506,000 km³. In comparison with the total volume of oceanosphere, these figures of exchange are insignificant. There is a much greater exchange between waters of the different oceans, that is, about 18,370 km³ of water is annually exchanged between the oceans. This process redistributes the oceanic reserves of heat and salt, and has a great influence on both atmospheric processes and the characteristics of the whole Oceanosphere.

1. The World Ocean 2. Glaciers and permanent snow cover 3. Ground water, permafrost 4. Lakes, rivers, bogs 5. Water in atmosphere

Oceanic water is a complex solution and there is a great diversity in its chemical composition. It differs from fresh water by having a greater diversity of dissolved chemicals, and therefore, Oceanic water has different properties than fresh (terrestrial) water. The total mass (in grams) of all solid substances dissolved in sea water is expressed as salinity in parts per million (⁰/₀₀). The average salinity of waters of the World Ocean is about 35⁰/₀₀, that is, about 35g of solid substances are dissolved in 1 kg of the water. Almost all chemical elements known on the Earth, have been found in Ocean water. They are in the forms of elements, molecules and as suspended matter.

The substances which are included in the structure of Oceanic water are conditionally divided into five groups: main elements, dissolved gases, biogenic substances, trace elements and organic substances.

Eleven main chemical elements comprise about 99.99% of the whole weight of dissolved substances, or about 47.8 x 10¹⁵tons, having the greatest influence on the physical properties of water. The stability of ratios between concentrations of main elements is the most important feature of its chemical structure.

Basically, dissolved gases in the World Ocean are nitrogen, oxygen, carbon dioxide, argon and hydrogen sulphide. The gases are derived from the atmosphere, biochemical processes in different layers of the water, at river mouths and estuaries, from degassing of the mantle into the Earth’s crust and from other geochemical processes. The weight of atmospheric gasses entering the waters of the World Ocean are on the order of 32.4 x 10¹² t. Most chemically and biologically-derived substances dissolved in the World Ocean are oxygen and carbon dioxide.

Biogenic substances, that is, inorganic concentrations of nitrogen, phosphorus and silicon, are consumed by water plants, mainly by phytoplankton. The concentration of biogenic substances is determined by the amount and degree of biological processes, ocean dynamics, and to a lesser degree, by coastal mixing and outpouring of rivers.

Trace elements, of which there are 60, are found in minute quantities in ocean water and comprise only 0.01% of the total sum of elements in the Ocean, or 0.33 x 10¹² t. They have practically no influence on the physical properties of sea water, but play an important role in biochemical processes occurring in the Ocean.

Organic substances are found in dissolved and suspended states in the water column. The greatest concentrations are seen in the surface layer of the Ocean.
 
 

1 - dissolved trace elements

Sea water has a number of unique properties that considerably distinguish it from other fluids. The most important physical properties of sea water are a high thermal capacity, high dissolving ability, density, low heat conductivity, transmission of light and sound and good electrical conductivity. In many respects, these properties depend upon temperature, salinity and pressure.
 
 

1. Lines of equal temperature (isotherms) in degrees Celsius(°C) 2. Average limits of sea ice distribution 3. Cross-sections

1. Isolines of salinity in parts per million (0/00) 2. Average limits of sea ice distribution 3. Cross-section

1. Isolines of oxygen in milligrams/atom per litre of sea water (mg-at O2/l) 2. Mean limit of sea-ice distribution 3. Cross-section

Warmer surface and near-surface layers transmit heat to underlying waters, forming a productive layer. Hydrological, biological and other processes act within it. The thickness of an active layer ranges from 200-400 m. Down to depths of 1,000-1,800 m, the temperature gradually decreases, and below 1800 m, cold waters of almost constant temperature exist.

The salinity of water in the surface layer of the World Ocean depends mainly on evaporation and atmospheric precipitation. In coastal regions, fresh water outflows near the mouths of rivers, and in polar regions, the processes of freezing and thawing of ice greatly influence surface salinity. Below than surface layer, the salinity field is formed as a result of the interaction between the transport of salts by currents and diffusion by the intermixing of waters.

High salinity (>35⁰/₀₀) is encountered in surface waters at tropical latitudes, where evaporation is greater than at other latitudes. The lowest average salinity of oceanic waters (~29⁰/₀₀) is observed in the summer in the Arctic Ocean. In coastal regions with significant river run off, salinity does not exceed 15-20⁰/₀₀. The salinity of deep and near bottom waters in the oceans about 35⁰/₀₀. Salinity and temperature together affect the density of water. Many physical characteristics depend on density distribution, for example, water exchange processes, intermixing and sound transmission.

Oxygen enters the Ocean from the atmosphere and also as a result of photosynthesis in phytoplankton in the upper layers of water. The oxygen content essentially depends on temperature. When temperature decreases, oxygen solubility increases. In deep layers, the oxygen content is mainly determined by processes of intermixing and transport of water masses by currents.

The total amount of dissolved oxygen in the Ocean is ~7.5 x 10¹² t, which is 158 times less than in the atmosphere. Oxygen is expended during respiration by marine organisms and by processes of oxidation. Oxygen saturation of the Ocean surface layers occurs only when the atmospheric oxygen budget is exceeded.
 
 

Light exposure on the Ocean surface depends on the altitude of the Sun, transparency of the atmosphere, cloud cover and weather disturbances. Sunlight on the Ocean surface is refracted and enters in the water, with a minor amount being reflected back into the atmosphere. Passing through the water, sunlight is dispersed at the expense of absorption and dispersion. More than 60% of transmitted light-energy is absorbed in the upper meter of sea water. In depths greater than 1,000 m, light has occasionally been detected, but only with the help of sensing devices.

The speed of sound transmission in sea water depends upon temperature, salinity and hydrostatic pressure (depth) of the water. Speeds range from 1440m/s to 1570 m/s. An increase of temperature on the order of 1°C causes a decrease in speed of approximately 4 m/s.

There are direct and indirect methods to determine the speed of sound in sea water. Direct methods require the help of instrumentation. Indirect measurement are made by calculating the sound speed based upon available temperature, salinity and depth data.

In the 1940s, layers were detected in the Ocean in which sound waves are transmitted over super-long distances in a so-called “underwater sound channel.” The axis of the channel is at the depth where the speed of sound is at a minimum. The sound is spread with the least transmission power loss and can travel thousands of kilometres in the channel axis. The axial depth of the underwater sound channel may be from 100 m and less in polar latitudes up to 1,500-2,000 m in the Tropics.

USC Axis of USC Upper boundary Lower boundary

The continuous motion of water is a major characteristic of the World Ocean. Water-mass movement in horizontal and vertical directions forms the general system of Ocean circulation. Deposition, evaporation, coastal drainage, horizontal non-uniformity of water density, tides, wind and atmospheric pressure are all related to a number of factors which cause a transitional motion of waters at the Ocean. With the origin of motion, there is a declining force of rotation of the Earth (Coriolis effect), which inclines the forced weight of water to the right in the Northern hemisphere and to the left in the Southern Hemisphere.

Circulation of surface waters is now one of the most investigated topics. Circulation represents a rotational system around a fixed geographical point. Each rotation permits the interconnected currents to widen, and increases the speed and volume, thereby mixing the waters.

One of the largest currents on the globe is the West Wind Drift, or Antarctic Circumpolar current. It is about 2,500 km wide with a maximum speed of 0.4-0.5 m/sec, and has a volume measured in the Drake Passage of 230 million m³/sec. The Gulf Stream current has a volume on the order of 80 million m/sec, and the Kuroshio current, 50-60 million m³/sec. The greatest speed of these currents 2-3 m/sec.
 
 

1. Cold currents 2. Warm currents  Speed of currents in m/sec 3. <0.25  4. 0.25-0.50  5. >0.5  The currents for summer in the Northern Hemisphere are shown in the chartlet.

In-depth studies of the structure and ocean dynamics has resulted in the discovery of ring-shaped motion (eddies) on the edges of large currents (Gulf Stream, Kuroshio etc.) as well as on the open Ocean, and these are called seasonal eddies. They are mainly formed as a result of the dynamic instability of currents and produce high-intensity cyclones and anticyclones. The life of some of these eddies ranges from several days to 3 and even 5 years. Their diameter can reach hundreds of kilometres, their depth distribution up to a thousand or more meters, and their speed of movement up to a few kilometres per day. The temperature contrast between eddies and the ambient waters can reach 10? C and more. In the open Ocean it is lower than on the edges of currents.

The discovery of synoptic eddies has an important value. They can complicate surface and submarine navigation, acoustic transmission calculations and change the density distribution of water. The differences in the sound speed between the centre of an eddy and its edge occasionally reaches several tens of meters per second.

Satellites, aircraft, drifting platforms and long-duration buoys are used for detection and the investigation of eddies on the Ocean.

Counter-currents are usually associated with surface currents, i.e., currents flowing an direction opposite to the main surface currents. These are known to exist widely, and can be found at the surface in Equatorial counter currents, and on the edges of the Gulf Stream and Kuroshio currents.

In the 1950s, subsurface and deep counter-currents were mapped. These were located in Equatorial zones of the Pacific, Atlantic and Indian Oceans They were named after Cromwell, Lomonosov and Tareev. Subsurface counter-currents flow from west to east. The entire system of counter-currents covers about 26,000 km, and moves up to 80 million m³ of water every second. It consists of three jets: the central, most powerful one is found on the Equator and two symmetrical jets, one in the Northern Hemisphere and one in the Southern Hemisphere. The Equatorial jet covers an ocean layer of 50-300 m and has a velocity of up to 1.5 m/s.

Deep counter-currents are also found under such currents as the Gulf Stream, Kuroshio and others. The upper boundary of counter-currents is at depths of 1,000-2,000 m. The speeds generally do not exceed 0.2-0.3 m/s. In 1967, speeds of counter-currents found under the Gulf Stream flow were measured at 0.01-0.18 m/s.

Counter-currents: 1.Lomonosov  2. Tareev  3. Cromwell

The main factors determining formation of deep water, are temperature and salinity.

The surface water is cooled in sub-polar regions of the World Ocean. Upon freezing, the salts are removed and this process increases the salinity of the adjacent water. As a result, the water becomes denser and descends. The areas where these deep waters are generated are in the Greenland Sea in the north and the Weddell and Ross Seas adjacent to Antarctica in the south.

From these sub-polar regions, deep waters are dispersed into the Ocean. Their speed is very slow. For example, Antarctic Bottom Water (AABW) travelling into the Pacific Ocean from the south requires ten years to arrive.

The distribution of deep waters is controlled by sea floor topography. For example, it has been found that North Atlantic deep waters, following the bottom relief, are partially derived from the Westwind Drift, which follows bottom topography from Antarctica.

Speed in m/s 1. <0.05  2. 0.05-0.15  3. Regions where deep water is formed

1. Wind 2. Ascent of waters

Coastal upwelling is caused by wind-driven surface waters and currents controlled by coastlines. Such currents can be generated by sustained winds blowing parallel to a coast, driving surface currents (governed by the Coriolis effect) while forcing them to deviate away from the shore to the right in the Northern Hemisphere and to the left in Southern Hemisphere.

The greatest upwelling has been observed on the coasts of California, Peru, Morocco, South Africa, Somalia and Western Australia. The extent of coastal upwelling zones can reach hundreds of km and their widths, tens of km. The speed of upwelling is basically insignificant. As an example, on the coast of California, it moves about 20 metres in a month, and the waters originate at depths of less than 200 m.

In the open Ocean, upwelling is most often associated with regions of diverging currents. The waters which have come to the surface carry a large number of different biota, which promotes primary production of basic elements of the food chain in the surface layer and makes zones of upwelling major fishing regions of the World Ocean.

In regions where convergent currents and strong winds act on coastal waters, downwelling occurs. Surface waters descend, thereby providing oxygen to deeper layers.

The surface of the Ocean is almost always in a state of motion. Wind waves and swells are most often observed. Wind waves are directly related to the wind, and when the winds decrease or die, swells are observed. Swells also originate from adjacent Ocean regions under the effects of winds. Waves spreading in the absence of wind are called “dead swells.” As a result of the interaction of wind wave and swells, “mixed waves” may occur.

The apparent motion of water masses is caused by the forward movement of waves.. The shape (profile) of a wave is the only part that actually moves. The particles of water in a wave move on circular orbits and have no forward movement. The wind disturbs the uppermost layer of water. With an increase in depth, the radii of the orbits decrease, and at a depth equal to one wavelength on the surface, the disturbance is practically non-existent. The basic elements of a wave are the crest and trough: the highest point is the crest and the lowest point is the trough. The wave height is the vertical distance from the crest to the trough. The wave length is the horizontal distance between two crests or two troughs. The period is the time it takes for a wave to pass until the next wave takes its place.

The size of wind waves depends on the speed, the duration of the wind and length of the fetch. Fetch is the distance a wave travels from the moment of its generation under the effect of a steady wind. The largest waves have been observed in the middle latitudes, where storm winds may blow at speeds of up to 30-50 m/s. The largest wave ever recorded had a height of 34 m and was observed in the North Pacific Ocean. Waves of up to 30 m have been observed in the Atlantic and Indian Oceans. The impact force of storm-generated waves can reach 50-60 t/m².

As a wave approaches the coast, it becomes shorter in length and more abrupt, increasing its height. Friction with the bottom causes the trough of the wave to disappear, the crest to slow its movement, and, when the depth causes the wave height to become 1.3 times the depth, the crest falls, forming a breaker. Breakers can be observed above elevated placed on the shallow sea floor (reefs and shoals), and can be seen from shore. At an abrupt shoreline, the breakers become stronger, making large splashes and have great destructive power.
 
 

1. Orbiting motion of particles 2. Wave-caused destruction at various bottom slopes

Internal waves most often arise at a boundary between water layers of different densities, where the particles of a water are in a condition of a steady-state equilibrium. Particles oscillate under the influence of wind and tidal waves, synoptic eddies, changes in atmospheric pressure and other phenomena. The oscillations are spread in denser water as internal waves with heights of 20-100 m. Their lengths can vary from hundreds meters up to several kilometres, and their period, from several minutes up to tens of hours. Internal waves react to cyclical changes of temperature and salinity at depth. Sometimes, during period of calm or weak winds they are observed in alternating, smooth bands on the surface of the Ocean. These bands are located above troughs of internal waves.

Internal waves influence the navigation of submarines, the overall performance of acoustic devices, migration of plankton and fish, etc.

1. Smooth bands 2. Oceanographic devices

Tidal oscillations are caused by the forces of gravitational attraction of the Moon and Sun, and the determining force is the gravitational attraction of the Moon. The top of a tidal wave appears to follow the Moon during its diurnal motion round the Earth.

The greatest tidal ranges are observed in a syzygy (during a full Moon and a new Moon), when Moon and Sun are on one line with the Earth. When a quarter Moon (quadrature) occurs, the Earth is at the point of a right angle formed by the directions of the Moon and Sun, and the tidal range is the lowest. The highest water level during one period of tidal oscillations is called, “high water”, and the lowest, “low water.” The tidal range is the difference between these levels.

The range and characteristics of tides in different regions of the World Ocean are variable. Apart from tidal ranges being affected by gravitational forces of the Moon and the Sun, the shape of the shoreline, bottom relief, depth, angle of approach of tidal waves to the coast and other local factors influence them.

On the open Ocean, tidal oscillations are insignificant, but on coasts they can be sizeable. For example, the greatest tidal range on Earth is in the Bay of Fundy (on east coast of North America in Canada), reaching 18m; in Penzhinskaya Guba of the Sea of Okhotsk it is 13m; on the northwest shores of Australia it is 11m and so on.

In the Atlantic Ocean, half-diurnal tides predominate, where a lunar day (24h 50m) regularly sees two high and two low waters. In the northern part of the Pacific and in Indian Ocean there are regions having diurnal tides, that is, where within a lunar day, there are almost always one high and one low water. Tidal onsets are accompanied by tidal currents, the speed of which can reach coasts at several meters per second.

The knowledge of tidal oscillations, ranges and currents is necessary for safety of navigation, nautical engineering, construction and for other kinds of economic activity. For this purpose, observations of time, range, height and the nature of tidal currents are routinely compiled and “Tide Tables”—prediction

In 1970, with the aid of radar altimeters placed on artificial satellites, the size and shape of our planet were made clear, and anomalies in the Earth’s the gravitational field were measured with a high degree of accuracy for the first time.

The anomalies are caused by effect of irregular mass distribution in the thickness of the crust and on the surface of the Earth. As a corollary, on the surface of the World Ocean there are stable areas of gravity “highs” and “lows” ("humps" and "holes").

It is possible to determine the sizes of anomalies on a chart of deviations of the surface of a geoid from an ellipsoid of revolution. The geoid and ellipsoid are the theoretical shapes of the Earth formed by gravitational and centrifugal forces. The highest "hump" (+78m) on the a relief of oceanic surface is observed in a region of the island of Papua-New Guinea, and the deepest "hole" (-112m) is found to the south of the Indian subcontinent.

The data on anomalies of the Earth’s gravitational field have an important use in solving a number of practical problems, particularly, for navigational purposes, studying the sea floor, searching for mineral wealth, etc.

Ice is the perpetual element of the landscape of the polar areas of the World Ocean. The primary masses of ice in the Northern Hemisphere is formed in waters of the Arctic Ocean and its seas. An ice season is observed also in Baltic, Bering, Okhotsk and in some other seas of the northern parts of the Atlantic and Pacific oceans. In the Southern Hemisphere, ice is formed in the seas and coastal waters of Antarctic Region.

Ice formation begins at negative temperatures in water. At a salinity of 24.7⁰/₀₀, the freezing temperature is -1.3°C, and at a salinity of 35⁰/₀₀, on the order -1.9°C.

About 12% of the entire surface of the World Ocean is covered with ice. In winter months the area of ice cover increases, and in summer months, it is reduced. For example, the area of ice around the Antarctic continent during the summer in the Southern Hemisphere covers and area of 5 million km²; in the winter, the ice cover is on the order of 20 million km².

Ice formation proceeds in several stages. In the beginning, the smallest chips of ice are formed and the surface of a water takes on an oily, leaden shade (“grease ice”). The ice chips then form needles, which, when frozen together, are transformed into an ice rind. Gradually, ice rind changes into a thin, elastic layer of ice about 5-10 cm thick, called an ice “crust”. With the increase of thickness, the elasticity of ice is lost, and under the action of wind and waves it breaks, by rubbing one piece against another, into pieces from 50 cm to 100 cm in size. Due to the friction, such ice-cakes acquire a round shape, similar to pancakes (“pancake ice”).

The following age-dependent stages of ice development of ice have been noted: young ice is grey and grey - white, with thicknesses of 10-30 cm; first-year ice is from 30 cm to 2m thick; residual first-year ice (older than first-year but which has not melted during the summer); second-year and multiyear-term ice. The multiyear ice can be 3-4 m thick.

The salinity of sea ice varies from 20⁰/₀₀ at the time of formation to 0.5⁰/₀₀ for multi-year ice.

At points where compression occurs in ice packs, pressure-ridges are formed, with heights of up to 15-20 m. At points where the ice pack separates, there are open “leads” of water.

Under the influence of prevailing winds and currents in the Arctic Ocean, the ice is driven through the Fram Strait between Greenland and Spitsbergen and farther, to the North Atlantic Ocean. In areas adjacent to Antarctica, ice has been observed to be drifting in a generally westward direction along the shoreline. As the ice drifts away from the Antarctic Continent, the ice-drift direction changes to north or northeast. Between 60°S and 52°S, the ice drifts in a generally eastward direction.

1. The greatest distribution of ice 2. The least distribution of ice 3. Predominant direction of ice drift

1. Wind 2. Currents 3. Atmospheric precipitation 4. Wind waves 5. Current-transport of heat 6. Downwelling 7. Heat flow through the sea floor 8. Direct Solar radiation 9. Reflected Solar radiation 10. Evaporation 11. Upwelling 12. Synoptic eddy

The mass of the waters of the World Ocean is greater than 280 times the mass of the atmosphere, and thermal capacity of water has almost 1250 times more thermal capacity than the air.

The surface of the Ocean absorbs 99.6% of incoming solar radiation, and only 0.4% is reflected. Heat also flows into the ocean from the sea floor but this heat is very insignificant. The Ocean, therefore assumes the role of a large accumulator of heat, and serves as source of energy and motion for the water. Heat accumulated by the surface layer is only partially lost by intermixing in with deeper layers of the sea. Primarily, heat lost during evaporation is absorbed by the atmosphere. Warm water vapours travel long distances, where they are cooled and form clouds which give off precipitation. When water circulation occurs, heat is exchanged (as are gasses and other substances) between the Ocean and atmosphere. Clouds also form when the atmosphere is warmed. The non-uniformity of atmospheric warming above the Ocean also results in the origination of winds which, in turn, produce drifting currents and storms.

Distribution of permanent atmospheric pressure centres (Aleutian and Icelandic lows, Azores high, etc.) promotes the generation of steady winds forming a system of general circulation on the waters of the World Ocean, including such strong currents as the Gulf Stream and Kuroshio, etc. On the edges of these currents, huge gyres containing upwelling and downwelling areas and internal waves are formed.

The processes of air - sea interaction are most intensive in zones of large differences in water and air temperatures.

As an example of the correlation of processes between the Ocean and atmosphere we can cite the existence of "El-Nino". A small branch of the Pacific Equatorial counter-current called "El-Nino" usually operates in the open Ocean to the north of the Equator, and has no influence on the climate of the west coast of South America. However, in some years, an easing of the easterly winds in the eastern part of the tropical zone of the Pacific Ocean. As a result, upwelling of deep waters decreases and an excessive area of the surface waters at Equator are warmed. The subsurface Cromwell counter-current rises to the surface along the shores of western South America and strengthens a current called "El-Nino", which penetrates far to the south, diverting the cold Peruvian current. On the coast, there are strong winds and excessive rainfall. The sharp increase in water temperature along the coast results in a massive economic loss to the local fishing industry, particularly in the catch of the Peruvian anchovy.

The study of the appearance of "El-Nino" has shown that it has an effect on the climate of the entire planet.

The understanding of the processes of air-sea interaction extremely important for weather prediction. Scientists from different countries have united in their efforts and study air-sea interaction under international programs. The first of such activities was the realisation of the First Polar year (1882). In 1970, the large, International Program of Research of Global Atmospheric Processes (PIGAP) was adopted. The outcome of this program was that new data with regard to thermal and dynamic conditions of the waters of the World Ocean and overall thickness of atmosphere were obtained.

On the "POLEX-North" and "POLEX-South" expeditions organised pursuant to PIGAP, it was found that a sizeable amount of heat from Equatorial regions is transferred to polar areas by oceanic currents and not by the atmosphere, as was earlier thought.. Studies of air-sea interaction continue to be an important field of research and will be in the future.
 
 

The floor of the Ocean has a complex structure caused by horizontal and vertical tectonic motions, breaks in the Earth’s crust, volcanic activity, sedimentation and other factors. The whole diversity of underwater relief forms is classified in the following main categories, including large areas of the Ocean: continental margins, transition zones, Ocean floor and mid-ocean ridges.

Continental margins are areas where a transition from continents to Oceans occurs. They include the continental shelf, slope, and foot. The shelf originated from a time when flat, coastal areas became inundated due to an increase in the height of sea-level from previous times. The width of the shelf varies, from tens to hundreds kilometres, and its depths can vary from 80-100m to as deep as 450-500 m.

The continental slope adjoins the shelf, framing the continental borderland. The slope can be slanted, moderately steep, cut by underwater canyons or step-like in which case the slope has a variable or blocky steepness. Slopes vary from 1°-2° up to 20°-30° and more. The bottom of the slope reaches depths of 3,000-3,500 m, where it changes to a very low grade of flatness at the continental foot. The continental foot is characterised by the existence of great thicknesses of sediment accumulations.

The transition zone is characterised by a change from continental crust to oceanic crusts. The densities of these crusts are very different. Island arcs, deep-water troughs and fringing basins are formed in the transition zone. The bottoms of basins are frequently flat, caused by the expanse of great thicknesses of sediments. However, they often contain rises, ridges and seamounts. The island arcs separate fringing basins from the Ocean, and are formed where oceanic plates collide. They are large underwater platforms on top of which are volcanoes or volcanic islands. The outer edges of island arcs are often bordered by narrow, steep-walled troughs and trenches some of which show depth maxima of up to 8,000-10,000 m.

The Ocean floor covers extensive areas and can be divided into a series of basins. The predominant depths of basins are 4,500-5,500 m. The surface of the Ocean floor is interrupted by ridges, plateaus, seamounts, guyots and underwater mountains chains. 

1 Continental shelf  2 Continental slope 3 Underwater canyons  4 Mid-ocean ridge  5 Transform fracture zone  6 Rift valley  7 Seamounts  8 The Ocean floor

1.Mid - oceanic ridges 2.Mid-Atlantic Ridge 3.North American Basin 4.Brazil Basin 5.Australian - Antarctic Rise 6.East Pacific Rise

1.East-Pacific Rise (centre ridge) 2.Cocos Plate  3.Nazca Plate 4.Pacific Plate

The Mid-Ocean Ridge, the great underwater mountain system of the World Ocean, can be traced for more than for 80,000 km. The ridges are mainly found near the middle of the ocean bed between continents, but can be seen close to continental margins in some cases. Ridges rise above the Ocean floor some 2,000-3,000 m and are often broken and offset by numerous cross-ridges and valleys. The active rift zone exists along the axis, where the highest heat-flow values from the depths of the Earth can be found. It occurs as a result of the spreading of lithospheric plates, rising from great depths in the mantle, and producing the oceanic crust. The Mid-Ocean Ridge is often cut by right-angle fractures called “transform faults” which are a series of separate units sometimes controlled by one-another, but all are expressions of great disturbances occurring deep within the Earth.
 
 

1.Underwater mountains 2.Active underwater volcanoes 3.Volcanic islands and atolls

The formation of underwater mountains has occurred over a broad range of geological periods, but have undergone changes as a result of the effects of external factors such as waves, currents, coral reef growth and possibly glaciation. As a result, some of these mountains have flattened peaks, and are called “guyots” or “tablemounts.” At one time, many of their peaks were probably above sea level, forming volcanic oceanic islands, but these were eroded by waves, after which the islands became submerged by collapsing and subsiding under their own weight, a general rise in sea-level, or a combination thereof. On some of the re-immersed mountains, coral reefs formed concurrently with subsidence, developing thick caps of coral limestone with thicknesses of up to 1,300 meters.

Terrigenous Calcareous Siliceous- calcareous Iceberg-rafted Siliceous Red ooze

Terrigenous sediments are found in layers on continental margins and adjacent parts of the sea floor. They are derived from the land and are dispersed by rivers, winds, ice, and also form when shores are eroded by waves and currents. The coarse material forms sediments basically in the coastal zone and in polar areas, the sediments are carried by icebergs and floating ice and deposited at great depths forming a glacio-marine sediment containing many boulders, cobbles and gravel. Sands are widespread on shallow parts of the shelves, around islands and on the tops of underwater mountains. In deep water sides on the outer continental shelves and on the sea floor, muds, silts and oozes predominate. A significant thickness of sediments on outer shelves and may become over-saturated with water and the slope fails, causing mud flows and submarine landslides, many of which travel downward in submarine canyons.

Biogenic sediments are formed from the remains of dead plants and animals. Depending on their chemical composition, they are divided into the categories of calcareous sediments, which are deposited mainly in tropical and middle latitudes, and siliceous sediments, found mainly in sub-polar and polar latitudes, especially around the Antarctic continent. Carbonate sediments on shelves are composed of fragments of clams, oysters, mussels and other shellfish, bryozoans, coral reefs, and on the Ocean bed, mainly from foraminifera which form oozes. From siliceous sediments, the most widespread are diatomaceous oozes.

In depths greater than 4,500-5,500 m biogenic sediments disappear because the carbonates dissolve under great pressures and remain in solution. They are replaced on the Ocean bed by polygenic sediments, which are characterised by red, deep-water clay, consisting from particles of different origins. One type is purely volcanic in origin, mainly from ash which falls from the sky near volcanically-active islands and island-arcs. Of limited distribution are chemogenic sediments, formed by chemical precipitation of salts from sea water and chemical processes at the bottom of the Ocean.

The thickness of the sedimentary cover at the Ocean bottom is non-uniform and depends on bottom relief and proximity to the source of the materials. Sedimentary cover is minimal on the crests of the Mid-Ocean Ridge, especially in fracture zones, and naturally, thickens with distance from the Ridge. In oceanic basins, the sedimentary thickness is from 0.5-2.0 km, and on and near continental margins the sedimentary cover may be 4-6 km, and in some places more than 10 km near the mouths of very large rivers, for example the Amazon River. Thickness also varies with the speed of accumulation. On continental margins and on the edges of basins, and in internal seas without outlets, sedimentation occurs at a rate of from 30 to 100 mm/1,000 years; and on the deep sea floor in the majority of areas, the sedimentation rate is less than 10 mm/1,000 years. In regions where red clay predominates the sedimentation rate is extremely small and does not exceed 1 mm/1,000 years.
 
 

1. Aeolean (wind) transported 2. Shore erosion 3. Transport by rivers  4. Transport by ground water  5. Yields of biological and chemical processes 6. Transport by icebergs and floating ice 7. Volcanic eruptions

1.Fjord, rias 2. Erosional, depositional 3. Coral, Mangrove  4. Ice  5. Delta, estuary

The World’s shorelines are almost 500,000 km long. The comprise the natural boundary zone between the land and the Ocean. A variety of shores, the result of the action of various natural processes such as storms, tidal and wind waves and currents, thawing and destruction by ice, outflow of fragmental material by rivers and the work of plants and animals. The large value has The greatest effect depends upon the geological structure of a coastal region, which determines the type stability of rocky materials and their breakdown and removal.

Extensive glaciation of continents in the recent geological past have resulted in repeated changes in sea level. During the period of the last glacial maximum (17,000-18,000 years before the present), sea level was 100-120 m lower than it is today. The tongues of glaciers in motion carved out valleys in coastal areas in higher latitudes. The increase in sea level caused by the thawing of glaciers caused inundation of glacial valleys and the formation of deep bays (fjords) in polar regions. In non-glacial areas, the flooded valleys are called “rias.” Such shorelines are widespread in regions where massive crystalline rocks were removed by erosion caused by tectonic uplift.

Waves and swell, and to a lesser degree, currents, not only destroy folded and/or friable rocks on erosion-formed shorelines, but also transport material along them. The transported materials that are eventually deposited in shallow waters form shoals, gravel berms and other forms of deposition. On shallow bottom slopes, the eroded rocks are disintegrated, and are deposited along the coasts. Together, these processes result in an equalisation of the coastline.

Biogenic shores are developed from the action of vegetation and animal activities. Such shores are widespread in temperate and tropical climates. Coral-built shorelines common in tropical latitudes, where they combine with the cemented remains of coral, calcareous seaweeds and mollusc shells. When conditions are right, there is a heavy growth of vegetation providing the environment to produce mangrove shores. Mangrove shores are low, swampy areas in tropical zones, where the intertwining of the air roots of mangrove trees trap suspended alluvium (particles of silt and sand) and prevent their moving out to create a depositional shoreline from forming.

Shoreline formation on the shores of polar seas occurs as a result of the thermal effect on the air and the water. Intensive mechanical weathering of frozen coastal rocks during formation of shores of the polar seas happens in an outcome of thermal effect of air and water. Intensive weathering of frozen coastal rocks in conditions of low temperatures of the air and water contributes to the productions of screes and slope collapses.

As an result of downstream transport of rivers, fragmental materials occupy the shorelines, forming deltas. These are produced mainly in tidal areas and have fan-shaped patterns. Alternately, estuaries are created at river mouths, which are affected by tides but do not have associated deltas.

The study of shoreline structure, formation processes and their development over time allows a prediction of coastline changes and depths to be determined. The results of these studies are useful for navigation, hydraulic engineering, construction of near-shore structures and for exploiting the resources in the coastal zones of the seas and Oceans.

1.Approaching waves 2.Shoal 3.Lagoon 4.Underwater sand bar

1.Wave fronts 2.Shoal 3.Lagoon

Waters of the World Ocean provide a favourable environment for live and the development of plant and animal organisms. If they are rich in oxygen and nutrients, they become bioluminescent. All organisms living in the Ocean are divided into three large groups: The vegetation (plants) such as seaweed and photosynthesising bacteria, using solar energy, transform biogenic nutrients using a process of photosynthesis. Also in this group are many bacteria that convert mineral substances to organic substances by a process called chemosynthesis. The second group, animals, consume plants and other animals. The Third group feeds on the remains of plants ad other animals and also serve as food for many organisms.

In the Ocean, therefore, a certain dependency exists between its living things. Food is the primary dependency, followed by the effects of life on Ocean productivity and then Man’s ability to use sea life as a resource.

The diverse vegetative and animal life in the Ocean is extremely non-uniform in its distribution. Next to areas with abundant sea life, such as zones of upwelling, there may exist areas that have almost no living matter. These are similar to deserts on land. On the globe there exist 63 classes of animals and 33 classes of plants, a basic part of which live in the World Ocean (76% of the animals and about 50% of the plants).

All specific varieties of the inhabitants of the Ocean, from single-celled organisms up to giant whales depend the existence of a population divided into three classes plankton, nekton and benthos, depending on where these organisms live.

Plankton include a huge quantity of organisms, which float in different layers of the Ocean and are transported by currents. Belonging to this class are bacteria, cell-like plants (phytoplankton), some kinds of molluscs, crabs, roe and larva of fishes, larva of invertebrate bottom animals and others (zooplankton).

Nekton consist of organisms which swim in deeper waters and are capable of travelling long distances. Fishes, cephalopod molluscs, marine mammals (whales (cetaceans), seals, sea lions and walruses (pinnipeds)), sea turtles and snakes all rely on them for food. Although nekton are important to large animals, the nektonic biomass is approximately 20 times less than that of plankton.

Benthos comprise a group of organisms living near the sea floor, attached to it, dug in or living in it for shelter. Organisms living on top of the sea floor also fit into this category It contains many kinds of molluscs, crabs, worms, echinoderms and sponges. Especially beautiful are the magnificent benthos on coral reefs. The primary plants in the benthos category are multicellular seaweed (green, red, brown), microscopic one-celled plants, wrack grass, thalassia and other grasses.

There are specific communities that confine themselves to the sea surface: birds. There are 240 kinds of birds - albatrosses, frigate-birds, gannets, shearwaters, gulls and many others that live and rely heavily on the Oceanic food chain.

The World Ocean as an environment for vegetable and animal organisms is subdivided as such: pelagic (living in the layers of water from the surface to the bottom) and benthic (living on the bottom of ocean)

In the pelagic class, epipelagic, mesopelagic, bathypelagic and abyssopelagic life forms live.

Epipelagic - the most inhabited the Ocean, extending from the surface of the Ocean up to depths on the order 100-200 m. The process of photosynthesis promotes the growth of organic substances. Therefore, biological processes observed in epipelagic zone are responsible for determining the life forms living in the other pelagic zones, where organic consumption occurs.

Mesopelagic - the "twilight" zone, located at depths from 100-200 up to 700-1,000 m. The seasonal and diurnal vertical migrations in the epipelagic zone are interconnected with searches for food are characteristics of the majority of the mesopelagic inhabitants. Vertical migration can be 600 m and more.

Bathypelagic - the zone of eternal darkness located at depths from 1,000 to 3,000 m. The quantity of living organisms is sharply reduced here, and is directly related to the decreasing volume of food descending from the upper zones. The specific varieties of fauna are also reduced.

Below the 3,000 depth and extending to the deepest parts of the ocean is the abyssopelagic zone. Inhabitants of the abyssopelagic zone are often colourless. The fishes and crabs most often have no eyes but some have special flashing organs used to assist them to find food.

For distribution of benthic organisms (living on the Ocean bottom) a number of zones have been allocated. The upper zone - littoral and sub-littoral includes places from the tide line to depths of about 200 m; bathyal includes the range from 200 to 3,000 m; abyssal takes in the zone from 3,000 m and ultra-abyssal takes in the zone from 6,000 m to the floors of the deepest trenches in the Ocean.

The littoral and sub-littoral are characterised by the greatest species varieties and abundance of food. Only in this zone does bottom vegetation develop..
 
 

I. Pelagic 1. Epipelagic 2. Mesopelagic 3. Bathypelagic 4. Abyssopelagic II. Benthic 5. Littoral, Sub-littoral 6. Bathyal 7. Abyssal 8. Ultra-abyssal

In 1977, American scientists conducted geological and biological research in the eastern part of the Pacific ocean, using the deep diving submersible, "Alvin". A major result of the research was the discovery of more than 2,000 m hydrothermal sources venting on the sea floor. These contained a liquid lava and was gradually forming tower-shaped structures with heights of tens of meters. Discoverers of the vents called them "black smokers". The temperature of the water near the outpourings of lava reached 350°C. In fields of the hydrothermal vents, real "the oases of life" were detected, occupied by organisms previously unknown to science. The research showed that in most investigated hydrothermal communities four kinds of bottom animals may exist and can be included in the biomass: “Riftia”(length up to 1.5m), bivalve molluscs (length up to 30 cm), “Bathymodiola” (length up to 15 cm) and a living pipes worm “ (length up to 10 cm).

Sources where oases of life exist: 1.Hot 2.Cold 3.Deep-water troughs 4.Mid-oceanic ridges

The basis for life of the numerous population of "oases" is the process of chemosynthesis, on which bacteria live. By consuming various inorganic compounds (hydrogen sulphide, sulphates, iron-manganese, etc.), these bacteria synthesise organic substances, from which their bodies are created. Bacteria - initial link of food chains - exist in hydrothermal communities of animals. Some animals, for example, worm-like creatures, feed by chemosynthesising bacteria in their worm tubes.

In 1986, an expedition of the Academy of Sciences of the USSR inspected hydrothermal sources located in the northern part of Kurile Islands on the research vessel "Mstislav Keldysh"

In the mid-1980s, "oases of life" were found in the Gulf of Mexican Gulf, and in deep-water troughs near northern Japan. There was a difference in the communities of animals living near hydrothermal sources. These "oases" developed using hydrogen sulphide travelling along with water leaked through cracks in the sea floor.

The discovery of exotic fauna in regions of outpouring of hydrothermal products coupled to an infiltration of brines has allowed the scientists to make new approaches to the history of the origin and development of Ocean fauna.