Download properties of oceans, inland seas, coastal zones, and estuaries

PROPERTIES OF OCEANS, INLAND SEAS, COASTAL ZONES, AND
ESTUARIES
N.N. Mitina
Institute of Water Problems, Russian Academy of Sciences, Moscow, Russia.
Keywords: Oceans, seas, inland seas, coastal zone, mouth areas of rivers, deltas, estuaries,
classification, morphology, continental slope, continental rise, continental shelf, abyssal,
currents, water masses.
Contents
1. Introduction
2. Oceans
3. Seas
4. Coastal zones
5. River mouth areas
6. Marine pollution
7. Science and the World Ocean
Conclusions
Related Chapters
Glossary
Bibliography
Biographical Sketch
Summary
Areas, depths, geomorphological and geological features of ocean, classification of seas, bays,
straits, different coastal zones and estuaries are described. Basic characteristics of Ocean water
(seawater), water masses and currents are given. Main course and features of marine pollution
and environment protection measures are discussed. History, problems and ways of the marine
science are considered in the article.
1. Introduction
The World Ocean is the body of water with a continuous water surface, occupying the largest
depressive geomorphologic feature of the Earth. It surrounds the continents and islands and has a
composition dominated by common salt. The total area of the World Ocean is 361.26 million
km2; this is about 70.8% of the Earths surface (61% of the surface in the northern hemisphere,
and 81% in the southern hemisphere). The average depth is 3711 m, and the maximum depth is
11 022 m in the Mariana Trench in the Pacific Ocean. The total volume is around 1340.7 million
km3. The World Ocean is considered as an open dynamic system, which exchanges matter and
energy with the contiguous natural spheres of the Earth. This exchange has the form of global
cycles, in which the heat, moisture, salts, gases and other materials that construct the "body" of
oceans and continents take part. During the whole Earths history these processes were self
regulated and aimed at natural stability. Humanity now threatens to destroy this stability by
industrial and other activities leading to negative consequences for nature.
The World Ocean plays a vital role in the global hydrological cycle and actively interacts with
the atmosphere in a way that is very important for the Earths environment. Persistent wind
systems transport huge air masses across the oceans and in and out of the land areas. More or
less stable currents carry their temperature characteristics to far-distant parts of the oceans,
affecting the climatic conditions in bordering lands. The annual inland evaporation of about
66 000 km3 occurring in dry air masses is transported as water vapor out to sea and is
precipitated. Of the 502 500 km3of water evaporated yearly from the ocean, a considerable
portion is carried by maritime air masses to the land, where total precipitation amounts to about
110 000 km3 annually. To compensate for the excess of precipitation over land evaporation,
42 600 km3 of water returns to the sea by runoff. In addition to this large-scale phenomenon,
there are numerous interactions between the oceans and land; these affect synoptic meteorology
and cause salt-water intrusion problems. The Ocean has vast energetic (tidal energy), mineral
(chemical substances dissolved in the water, mineral resources) and biological (fish, mollusks,
crustaceous, algae) resources. It supports life forms even at maximum depths (11 km), not only
in the euphotic layer.
2. Oceans
The World Ocean is divided into oceans, seas, bays and straits (see Figure 1).
Figure 1. Major basins of the World Ocean. Source: Philips Atlas of the World. Introduction to
World Geography. (1997). George Philip Limited, UK (modified).
Oceans are the major parts of the World Ocean, which have independent basins, being semiisolated by surrounding continents, and having:

independent systems of atmospheric circulation which determine
the variety of climatic conditions over the surface,

independent systems of surface and deep currents and therefore
independent horizontal and vertical systems of distribution of
hydrological, hydrochemical and biological features.
There are essentially four oceans: Pacific, Atlantic, Indian and Arctic. Their areas are 49.9%,
25.7%, 20.5% and 3.9% accordingly (see Table 1). The term "Southern Ocean" is often used, but
this area has no independent abyssal basin (its area is 86 millions km2).
Table 1. Basic data on the oceans Source: Philips Atlas of the World. (1997). Source for average
depth: Fundamental Soviet Encyclopedia (1979). Moscow, BSE.
Among the main geomorphological and geological features of oceans, we can distinguish:

underwater edges of continents,

transitional zones from oceans to continents, in particular the
systems of islands,

ocean basins which include the abyssal plains (bottom) of oceans,

mid-oceanic ridge zones, and

submarine mountains (see Figure 2).
Underwater edges of continents combine the three relief elements: 1) continental shelf, 2)
continental slope and 3) continental rise. The common feature for these three parts is similarity
in continental composition, composed of three layers: sedimentary, granite and basaltic layers.
Figure 2. Distribution of rifts (Mid-Ocean Ridges), trenches and slippage
Continental shelf: part of the continental margin with a flooded gentle slope (slope less than
1:1000) and having a common geological structure with the continent, located between the
coastline and the line where the slope sharply increases. The width can vary from a few
kilometers to 500 km. As a rule, the continental shelf boundary is situated at a depth of 100 to
200 m. The shelf of the Arctic Ocean is the widest (up to 400 km) and the shelf around
Antarctica is the deepest (to 350 m).
Continental slope: the underwater edge of a continent located between the shelf and the ocean
basin, dropping from 100-200 m to 1500-3500 m with steep slopes (more than 4o, and in some
places from 35o to 90o. and abrupt relief (breaks, canyons). Transport of sediments as mud-floods
are characteristic of this relief form.
Continental rise: the plain adjacent to the lower part of the continental slope and inclined to the
ocean bottom. A gently sloping zone (up to 10-12) to a depth of 2000-3600 m adjacent to the
(steeper) continental slope. The continental rise is formed by a thick layer of sediment,
accumulated at the base of the continental slope as a result of sediment transport from the
continental shelf and continental slope (Schukin, 1974).
Abyssal plain: a wide accumulative plain area with average depth of 4-6 km. A peculiar feature
of ocean basin topography is the system of Mid-Ocean ridges or rifts, which stretch for a total
of more than 60 000 kilometers along the middle of the bottom of the Atlantic, Pacific, Arctic
and Indian Oceans. This is a great cordillera-type mountain system, 1-3 kilometers high over the
ocean bottom, delimited by steep slopes. The spreading process is coincident with the mid-ocean
ridges. The presence of rift valleys 25-50 km wide along the ridge axis, and perpendicular
transform faults are typical for mid-ocean ridges. The average depth of the rift zone is about 3.0
km.
2.1. Characteristics of Ocean Water (Seawater)
Seawater is generally composed of water, solids, and gases. The physical properties of seawater
are different from those of fresh (river) waters not only with regard to concentration of salt but
also as regards temperature and pressure. The solids include suspended particles of inorganic
matter, living organisms, and organic detritus, in addition to salts. The ratio of total solids to total
sample of seawater is known as the salinity. The ratio of the halide ions (C1-, Br-, and Imeasured by chemical titration) to total sample of seawater is approximately what is known as
the chlorinity. Both salinity and chlorinity are expressed in parts per thousands or per mille,
denoted by promille (). More then 99.9% of the salinity of ocean water is due to eight ions, the
two most important of which (Na+ and Cl-) are the constituencies of common salt. The
proportions of the salts, as percentages by weight, are shown in Figure 3.
Figure 3. Principal ions in seawater.
Source: Skinner B.J., & S.C. Porter, (1994). The Blue Planet. An Introduction to Earth System
Science. John Wiley &Sons, Inc. USA.
In some parts of the World Ocean, waters may significantly differ in quantitative salt
composition. The total solids in typical seawater are almost completely ionized. The most
important factors effecting salinity are (1) evaporation, (2) precipitation, (3) inflow of fresh
water, and (4) freezing and melting of sea ice. Average salinity of seawater is about 34.75. The
salinity of the seawater normally ranges between 33 and 37 and is related to latitude (see Figure
4). High salinity values occur in tropical and subtropical waters where evaporation exceeds
precipitation. The highest salinity levels occur in enclosed seas such as the Arabian Gulf, and the
Red Sea.. Salinity values generally decrease both north and south of the equator, but low values
are also found off the mouths of large rivers.
Figure 4. Average surface salinity of the World Ocean.
Source: Skinner B.J., & S.C. Porter, (1994). The Blue Planet. An Introduction to Earth System
Science. John Wiley &Sons, Inc., USA.
Seawater density and some other physical properties depend almost entirely on temperature,
salinity, and pressure. Average density of the World Ocean waters is1045 ton/m 3. The maximum
density of seawater is reached at a temperature of 4 oC, high salinity and high pressure. When
water in a certain region of the sea possesses a definite temperature and salinity for a wide
variety of conditions, it forms a continuous water mass. Water that is less saline or cooler is
more compressible. The vapor pressure over ocean water is somewhat lower than that over fresh
water, depending on salinity. Because of the salinity, the freezing point of seawater is lower than
that of fresh water. Since, on average, the specific heat of ocean water is much higher than that
of fresh water, the temperature variation in seawater is much lower than that of the fresh water.
The temperature in the open ocean varies between about 32 C and the freezing point, -2 oС. Two
types of ice can be formed in the oceans: frozen seawater, and icebergs, which are broken-off
pieces of glaciers. The average annual temperature of the surface waters in the World Ocean is
17.5 С; the highest average temperatures are found at the equator (up to 28 С), while moving to
the poles it drops down to -1.9 С). Seasonal temperature fluctuations occur to a depth of 100 to
150 meters. More than half the ocean surface is warmer than 20 C (see (Figure 5). About 93% of
the ocean volume is colder than 10 C and 76% is colder than 4 C.
Figure 5. Average surface temperature of the World Ocean: A) in February, and B) in August.
The horizontal variation of the surface temperature of seawater depends on many factors: solar
radiation, wind action, ocean currents, evaporation, precipitation, and river inflow. The vertical
variation in temperature allows us to recognize several consistent layers. The near-surface layer
temperature is close to that of the lower layer of the atmosphere, and it decreases gradually with
increase in depth. This layer is followed by a thermocline layer, which is characterized by
rapidly decreasing temperature with depth. Below the thermocline is a deep-water layer in which
temperature gradually decreases again with depth and until it reaches constant low temperature
of the bottom-water layer. In the bottom layer the temperature is 1.4 to 1.8 С, while in the polar
regions it is lower, at 0 С). The thermocline layer has a mean thickness of 200 meters. It can be
permanent and can extend to more than one kilometer deep. It may also be shallow and vary with
the seasons, thus becoming known as a seasonal thermocline. At great depth the temperature
distribution is determined by deep circulation, which imports water from the surface. Water
circulation in the layer down to 150-200 meters is determined mostly by the winds prevailing
over the Ocean; beneath this layer circulation is mainly attributable to variations in density in the
water layers.
2.2. Current Systems
Ocean currents are of many types. Drift, or wind currents are those developed from friction
exerted on the sea surface by steady blowing wind. Slope currents are caused by inclination of
the water surface developed by wind, barometric differentials, or inflow from rivers. Density
currents are caused by difference in density of the water. Tidal currents are caused by tidal
actions. To satisfy the law of continuity of flow, compensation currents are developed to fill the
spaces left by activating currents. Currents may also be generated by internal waves propagated
along surfaces of large density discontinuity within the body of the sea. The direction taken by
ocean currents is also influenced by the Coriolis effect.
The principal elements of surface ocean currents are developed in response to atmospheric
circulationmainly anticyclone cycles in subtropical latitudes and cyclone cycles in high latitudes.
Low-latitude regions in the trade wind belts are dominated by the warm, westward-flowing
North and South Equatorial currents. In their midst, and lying in the doldrums belt of light,
variable winds, is the eastward-flowing Equatorial Countercurrent. Each major ocean current is a
part of a large sub-circular current system called a gyre. Within each gyre different names are
used for different segments of the current system. Figure 6 shows the Earth's six major ocean
gyres. Currents in the northern hemisphere gyres circulate in a clockwise direction; those in the
southern hemisphere circulate counterclockwise.
Figure 6. Surface currents for a hypothetical ocean surrounded by land.
Source: P.K. Weyl, Oceanography: An Introduction to the marine environment.
Copyright 1970 by Wiley.
The actual circulation is very similar, with continents limiting flow and forcing oceanic
gyrations. In each major ocean basin, westward-flowing equatorial currents are deflected
poleward as they encounter land. Each current thereby is transformed into a western boundary
current that flows generally poleward, parallel to a continental coastline. In the North Atlantic
Ocean this current is called the Gulf Stream, while in the North Pacific it is the Kuroshio Current
(see Figure 7). In the South Atlantic the Brazil Current follows the South American coast, while
in the Pacific and Indian oceans the corresponding currents are the East Australian Current and
the Mozambique Current. On reaching the belts of westerly winds, the Kuroshio Current changes
direction to form the North Pacific Currents on the poleward side of the North Pacific gyre,
while in the Atlantic, the Gulf Stream passes eastward into the northeast-flowing North Atlantic
Current. In the southern hemisphere, the poleward moving waters of the Brazil, East Australian,
and Mozambique currents enter the Antarctic Circumpolar Current that circles the Earth near
latitude 60S. At the southeastern ends of the southern hemisphere gyres, cool southern waters
move northward along western continental coasts forming the West Australian Current in the
eastern Indian Ocean, the Humboldt Current along the southwestern coast of South America, and
the Benguela Current off the southwestern coast of Africa (Kennish, 1997).
Figure 7. Prevailing surface ocean currents in the northern hemisphere in winter.
The top figure represents the condition in summer in Indian Ocean. (1) East Greenland Current,
(2) Labrador Current, (3) North Atlantic Current, (4) Gulf Stream, (5) Antilles Current, (6)
Canaries Current, (7) North Equatorial Current, (8) South Equatorial Current, (9) Guiana
Current, (10) Brazil Current, (11) Falkland Current, (12) Circumpolar Current, (13) Benguela
Current, (14) North-East Monsoon Current, (15) South-West Monsoon Current, (16) Equatorial
Countercurrent, (17) South Equatorial Current, (18) Somali Current, (19) Agulhas Current, (20)
West Australian Current, (21) North Pacific Current, (22) Oyashio Current, (23) Kuroshio
Current, (24) North Equatorial Current, (25) Equatorial Countercurrent, (28) South Equatorial
Current, (29) Peru Current, (30) Cape Horn Current.(Source: Kennish M.J. (1997) Practical
Handbook of Estuarine and Marine Pollution. CRC Press Marine Science Series).
The northern Indian Ocean exhibits a unique circulation pattern in which the direction of flow
changes seasonally with the monsoons. During the summer, strong and persistent monsoon
winds blow the surface water eastward, whereas in winter, winds from Asia blow the water
westward.
The wind currents over the Equator periodically deviate from the normal, leading to changes of
ocean currents and suppression of the upwelling. In a normal year, southeasterly trade winds
drive surface waters westward off the region of South America, drawing cold, nutrient water up
from below. In an El Nino year, which occurs every 2-7 years, warm water from the western
Pacific suppresses upwelling in the east depriving the region of nutrients, and disturbing the
tropical atmospheric circulation. During an intense El Nino, the southeast trade winds change
direction and become equatorial westerlies, resulting in climatic extremes in many regions of the
World, such as Australia, India, UK, and southeastern USA.
Major Water Masses
The water of the oceans is organized vertically into major water masses, stratified according to
density (see Figure 8). The identity and sources of these masses have been determined by
studying the salinity and temperature structure of the water column at many places. The Atlantic
Ocean provides a good example. In the Atlantic, water in the surface zone forms a central water
mass north and south of the equator to about 35 latitude. The temperature of this water typically
ranges from 6 to 19 C (43 to 66 F), and the salinity ranges from 34 to 36.5.
Figure 8. Main water masses of the World Ocean. 1- Polar, 2 Sub-polar, 3 Moderate-tropical, 4
Tropical, 5 Equatorial, 6 Indo-Malaysian, 7 Near- Mediterranean, 8 North-Atlantic (Source:
Stepanov V.N. (1983) Ocean-Sphere. M., Musl.)
Cooler subarctic and subantarctic surface water masses are found at high latitudes where cool
temperatures and high rainfall give rise to colder, less saline waters. The largest polar surface
water mass, flowing as the Antarctic Circumpolar Current, moves clockwise around Antarctica.
Its temperature is 0 to 2 C (32-36F), and its salinity 34.6 to 34.7. The central water mass of the
Atlantic overlies an intermediate water mass that extends to a depth of about 1500 m. The
Antarctic Intermediate Water mass, the most extensive such body of water, originates as cold
subantarctic surface water that sinks and spreads northward across the equator to about 20N
latitude. Its temperature ranges from 3 to 7 C (37-45 F), and its salinity lies within the range 33.8
to 34.7. Water entering the Atlantic from the Mediterranean Sea is so saline (37-38) that it flows
over a shallow sill at Gibraltar Strait (-400 m) and downward beneath intermediate water to
spread laterally over much of the ocean basin.
In the North Atlantic, the deep ocean consists of a deep-water mass that extends from the
intermediate water to the ocean floor. This dense, cold (2 to 4 C, or 36 to 39 F), saline (34.8 to
35.1) North Atlantic Deep Water originates at several sites near the surface of the North Atlantic,
flows downward, and spreads southward into the South Atlantic. The deepest, densest, and
coldest water in the Atlantic is the bottom water mass that forms off Antarctica and spreads far
northward; in the Pacific it reaches as far as 30 N latitude. Because of its greater density,
Antarctic Bottom Water flows beneath North Atlantic Deep Water. It forms when dense brine,
produced during the formation of winter sea ice in the Waddell Sea adjacent to Antarctica, mixes
with cold circumpolar surface water and sinks into the deep ocean. This dense water has an
average temperature of -0.4C (31F) and a salinity.of.34.7.
The major currents are large-scale features of the ocean water masses and surface. Finer-scale
ocean surface movementwavesare also responses to the interaction of the atmosphere and ocean
surface and, in the near-shore zone, a response to movements of the solid Earth. The size of
surface waves depends how fast, how far and how long the wind blows. Storm waves are
produced by hurricane-force winds (>115 km/h) blowing for several days across thousands of
kilometers of the open water surface (Kennish, 1997). Severe thunderstorms over tropical and
subtropical oceans provide tornadoes. One or more tornado funnels may form within the tornado
cyclone as it moves with the thunderstorm. The low pressure and a strong winds account for the
destructive nature of tornadoes. A large earthquake or other brief, large-scale disturbance of the
ocean floor, such as a landslide or volcanic eruption, can generate a tsunami. Hawaii is
especially susceptible to dangerous tsunamis approaching from the earthquake regions of the
Pacific basin. The whole water mass in the Ocean is also subjected to the tidal forces of the
Moon and Sun.
3. Seas
A sea is a part of ocean more or less isolated from it by land, islands or uplands of the
underwater relief; it differs from the open part of the ocean in certain physical-geographical
features, mostly in its own hydrological and climatic regimes as well as differences in
precipitation, flora and fauna. The geographic configuration of the seas conditions the impact of
land on them, particularly as regards temperature and currents. Secondly, rivers influence the
seawater regime. They carry a vast amount of fresh water and suspended matter, and thus affect
salinity and the composition of bottom sediments. The limited connection with the open ocean
normally results in reduced water-exchange, which increases the influence of land factors as well
as development of intra-basin processes of eutrophication and reduced oxygen levels. The
greater the isolation of a sea, the more the land influences the sea and the greater the difference
from the ocean.
From a geological point of view, todays seas are young: they all have been finally formed when
the ocean level was close to modern level, in the Quaternary period. The deepest seas formed in
fault zones (for example the Mediterranean Sea, which has a maximum depth of 4594 m).
Shallow seas formed by flooding of the marginal zones of continents by the waters of the World
Ocean as a result of their sinking, or rising of the Ocean level; they are therefore situated on the
continental shelf. In seas of the temperate zone terrigenous sediments are formed, but in the
tropical zone chemogenous, as well as biogenous organic sediments (coral, shell) are mixed with
terrigenous material.
3.1. Classification of seas
There is no conventional classification of seas based on the whole complex of their features.
Various classifications are based on separate features (physical-geographical, morphological,
hydrological, tectonic). According to the degree of isolation and peculiarities of hydrological
regimes, seas are classified as inland, marginal and encircled with islands; according to
geographical position they are classified as mediterranean and continental, and according to
tectonic composition they are divided into platform (shelf) and geosynclinal (see Figure 9) (Sea
Geomorphology, 1980). Two large water bodies, the Caspian and the Aral, are commonly known
as Seas, but from a geographical standpoint, these are lakes. Similarly, not all seas are given the
name Sea, e.g. the Gulf of Mexico, Hudson Bay, and the Arabian Gulf.
Figure 9. Classification of seas
The following paragraphs describe the different kinds of seas.
Shelf seas (synonym: continental, epicontinental, platform) are situated on the shelf as a whole,
on continental parts of the Earths crust and are the submerged parts of continents covered by
seawater. Shelf seas are usually shallow (up to 100 to 200 m), but in the regions of modern
(Antarctic zone) or Quaternary (Barents, Kara Seas) glaciations they can have intra-shelf grooves
and depressions with depths of 500-1000 m.
Geosynclinal seas (seas of geosynclinal regions). These sea are adjacent to contemporary
geosynclinal systems (e.g. the Bering, Okhotsk, Caribbean, etc.) as well as superimposed
depressions (e.g. the Black Sea). The Earths crust under the bottom of a geosynclinal sea is of
oceanic or transitional type; the sediment layer is thick, relief is complex with a steep continental
slope and a deep basin, often complicated by underwater ridges. Geosynclinal seas are associated
with seismic activity and, sometimes, vulcanology. Normally within limits of geosynclinal seas
(e.g. Bering, East China, Okhotsk) there are vast platform territories (continental shoals).
A basin sea is a sea water basin, the bottom of which is a clearly defined deep depression,
limited on all sides by slopes. Such seas are normally located within limits of mountain or
modern geosynclinal belts (e.g. Black, Bering, Okhotsk, Japanese, Bahama, Caribbean).
According to tectonic features, basin seas may be regarded as a type of geosynclinal sea;
according to physical-geographical features they may be adjacent or mediterranean.
A marginal sea is a part of the ocean adjacent to a continent and partly isolated from the ocean
by peninsulas, islands or underwater uplands. They have comparatively free water exchange with
the ocean. According to tectonic features they are divided into shelf seas (North, Barents, Kara
Seas) and basin seas (Okhotsk, Bering, Andaman Seas).
A sea encircled by islands (or inter-island sea) is a part of the ocean surrounded by a more or
less tight ring of islands. They are normally characterized by free water exchange with the ocean,
and strong currents and tides (for example, the seas of the Malayan archipelago). Sometimes, the
narrowness of the gap between islands prevents free water exchange with the open part of the
ocean (for example, the seas Java, Banda, Zulu).
An inland sea is a sea that cuts deep inland and communicates with the ocean and adjacent seas
by one or more narrow necks. It is characterized by isolation from the ocean and weak water
exchange. The influence of the land and weak water exchange with the ocean, produce changes
in the water composition of inland seas (e.g. changes in salinity, sometimes hydrogen sulfide
pollution, eutrophication) and in the character of sediment formation. According to geographical
position inland seas are divided into continental (for example, Black, White Seas) and
mediterranean (for example, the Mediterranean and Red Seas).
Continental seas cut deep inland within a single continent (for example, the Sea of Azov, White
Sea, Hudson Bay). They are formed as a result of land submergence and flooding by ocean
waters.
A mediterranean sea is a part of the ocean situated between continents and connected with it by
one or several channels (e.g. the Mediterranean and Red Seas).
3.2. Inland Seas
We will now give further examples of the Eurasian inland seas. The inland seas of Eurasia all
appeared in the recent geological past, and have a tectonic origin. During their history the
majority of the seas had interrupted links with the ocean, becoming lakes for a period, and
changing their salt composition and water level regime. Features of the inland seas are
conditioned not only by their history and environmental influences, but also by bottom and
coastal relief, including the morphology of the straits through which water exchange with the
ocean takes place. Their features are also conditioned by climate, by rivers flowing into the sea,
their sizes and hydrochemical peculiarities, and also by anthropogenic impact in the watershed
areas of these rivers, in the coastal zone and water surface of the sea. Water balance of the inland
seas is heavily influenced by atmosphere precipitation, flow from the continent, evaporation
from the sea surface, and intensity of water exchange with the ocean. All these conditions define
the peculiar and unique character of inland seas (Table 2).
Lack of river water inflow combined with a warm dry climate that promotes high evaporation,
leads to high salinity of seas, either of the whole volume (the Red Sea), or parts of it (the
Mediterranean Sea). Thus the average salinity of the Red sea close to Suez Canal and the Gulf
of Aqaba is more than 41.5 (the highest salinity of the World Ocean). In the northern part of the
Red Sea it is 40.5 to 41, and in the southern, 38 to 39.
Table 2. Characteristics of some inland seas
In the Mediterranean Sea during the period of winter cooling in regions with high water
density, intensive convective intermixing take place, which lead to formation of intermediate
warm waters with high salinity in the Eastern basin and deep waters in the north of the Western
basin, in the Adriatic and Aegean Seas. The near-bottom temperature and salinity the
Mediterranean Sea is one of the warmest and most salinized seas of the World Ocean (12.6 to
13.4 оС and 38.4 to 38.7 respectively).
In the Black Sea dissolved oxygen is observed only in the upper water layers; its content near
the surface is 8 to 9 mg/l. Below 150 to 200 m the sea water is "polluted" by hydrogen sulfide,
the concentration of which close to the bottom is up to 11 to 14 mg/l. The oxic-anoxic boundary
has been steadily rising and at times reaches the surface. It is considered that the hydrogen
sulfide in the Black Sea is formed mostly as a result of the vital functions of sulfate-reducing
bacteria, the intense water stratification and weak vertical water exchange (FSE, 1980).
According to L. Mee (1992), this phenomenon is probably related to the decrease of river
inflows.
In the Azov Sea the principal phenomenon of interest is the contribution of fresh water. The
salinity balance is not stable and changes in response to seasonal and year-to-year climatic
conditions, as well as in response to reduced river flows as a result of agricultural activities in the
catchment areas, mainly withdrawal of water for irrigation, etc. Today the average input of fresh
water (coastal flow + precipitation on the sea surface) exceeds evaporation from the sea surface
by 8 km3 per year, but in unfavorable years (low flow, high evaporation) the fresh water balance
becomes negative and inflow of saline waters from the Black Sea through the Kerch Strait
exceeds the outflow of Azov Sea waters, resulting in ecological catastrophe.
During pre-glacial time there was dry land in the area of the Baltic Sea. During the last
glaciation the sea basin was completely filled with the ice. Sinking of land in the region of the
Denmark Strait took place about 7000 years ago, re-establishing links with the World Ocean.
The climate of the Baltic Sea is marine humid and is characterized by comparatively low
seasonal variations in temperature, frequent and fairly evenly distributed precipitation through
the year, and intensive cyclonic activity during the autumn-winter months. Hydrological
conditions are defined mostly by excess of fresh waters due to the continental river flow, and by
water exchange with the North Sea. The amount of water that comes with precipitation (172
km3/year), is equal to the amount of evaporation. The salinity of the surface water reduces away
from the Denmark Straits from 11 to 6-8 in the central part of the Baltic Sea. In the Gulf of
Bothnia it is only 4 to 5%о (and in the northern part of the bay, 2). In the Gulf of Finland salinity
is 3 to 6 (and in the upper part of the bay 2 and even less). Freezing begins normally in the
beginning of November in the north of the Gulf of Bothnia and achieves its maximum extent at
the beginning of March. By this time most of the Riga, Bothnia and Finland Gulfs are covered by
immobile ice. The central part of the sea is usually free of ice.
Like the Baltic Sea, the basin of the White Sea, with which it is closely connected in history,
was filled with ice during the last glaciation. It was only during the recent period in which the
climate has been affected by human activity, that the edges of the ice retreated and the basin was
filled by sea waters. The position of most of the White Sea to the north of the Arctic Circle
enables us to consider this water surface as subpolar and subarctic. The climatic features of this
region and several specific features of the hydrological regime of the White Sea are conditioned
by this situation. The White Sea freezes annually and is under ice for 7 to 8 months, from
October to May. There is a system of constant flows from the White Sea to the Barents Sea,
removing the surplus water derived from flows from the continent (in the spring-summer period
the continental flow is greater), and by the excess of precipitation over evaporation. The bottom
relief of the White Sea has the form of a bowl, separated from the Barents Sea by a shallow strait
at to the narrow entrance to the gulf. This prevents water exchange between the deep layers of
the Barents and White Seas. This is why the deep waters (deeper than 100 m) are constantly
saline (30) and have a constant temperature (-1.4 оС).
4. Coastal zones
The coastal zone is a strip of land and associated sea with relief forms and sediments created by
the sea under its present average perennial level. The coastal zone consists of the coastal
underwater slope coastline, and the seacoast. The coastal underwater slope is situated within the
limits of the wave base zone. In accordance with the theory of wave processes, the inner edge of
this zone is at a depth equal to the half of the biggest storm wave length in the deep sea. The
motion of wind-driven surface waves terminates downward at the wave base, a distance of
several dozens of meters to several kilometers. A wave breaks in shallowing water as interface
with the bottom causes the wave to grow higher and steeper. Waves approaching a shore are
refracted as the wave base reaches the bottom, realigning the wave so that it reaches the shore at
a gentler angle. During this process, surface waves modify the underwater relief of the wave base
zone, lifting light sediments and removing them as suspended load to greater depths. The
coastline is an average long-term perennial position of the water edgethe line of connection of the
coast with the sea surface without waves and tides. During the receding phase of the upswash the
ground surface exposes, while during the advancing motion the coastal zone is flooded by
seawater. If enough sediments are accumulated in this zone, they form specific, very changeable
accumulative relief form, called a beach. Conversely, cliff and bench are related to abrasion
relief forms of the coastal zone.
In the tidal seas and during wind-induced surges the upswash zone migrates along the flat coast
in accordance with the range of water level as well as the relief and the coastal and underwater
slopes. In this case the upper border of the underwater coastal slope is the water level under low
water or the wind effected low water, while between it and the beach one more geomorphologic
element is formedtidal flat, or littoral. One of the peculiarities of the seas and ocean coastal
zones relates to their position at the meeting point of the principal natural spheres of the Earth.
This is the area of interaction of the processes that take place on land, in the atmosphere, in the
sea and on the bottom of the sea. Thus, the sea shallows are complex ecotones, formed on the
borders land-sea, freshwaters-seawaters, water-bottom, water-atmosphere, land-atmosphere. As
an example, the benthic ecotones are transitional zones between communities of loose and dense
grounds, and silty and sandy grounds. In the pelagic zone, typical ecotones are formed at the
transition of different water masses, for example:

a layer of sudden change of temperature (thermocline);

a layer of sudden change of density (pinocline);

a layer of sudden change of salinity (halocline);
Like other ecotone systems the sea shallows play a role as natural filters, membranes, and
barriers and are the zones of "ecological tension", where physical, chemical and biological
processes are especially intensive. The common feature of ecotones is the "marginal
effect"increase of variability and abundance of organisms compared to adjacent biotopes and
biocoenoses.
In the modern stage of the World Ocean the most accessible and best studied is the coastal zone.
It is the most productive zone of the World Ocean, but intensive study is also necessary because
of the scale of industrial development and other anthropogenic impacts on the coast, in addition
to problems associated with exploitation of natural resources and pollution. The fact that 91% of
fish and seafood are produced in the shelf zone speaks volumes. Concentration of industrial
activity and exploitation of fossil fuels leads to pollution. Shallows and shoals are the zones
mostly influenced by pollutants, even in regions where the coastal belt is not developed and is
sparsely populated. In such cases pollution comes with river flow and its impact on biota can be
significant.
Although limited in area, the shallow seas play a global role in biological productivity and
biodiversity. as Along with their associated fresh and brackish water ecosystems they comprise
the main bioproduction zone of the World Ocean, where the principal world resources of fish
and seafood are concentrated (see Figure 10). They are also richly endowed with oil and gas
fields and other mineral resources.
Figure 10. World fishery regions. Source: Philips Atlas of the World. Introduction to World
Geography. (1997). George Philip Limited, UK, modified.
Thus, the shallow seas are the most vulnerable parts of the hydrosphere, suffering from the
influence of industrial and other human activities. The most productive parts of the shallow seas
are estuaries and river mouth areas. People deliberately cause major ecological change, often
without taking into account all the interactions in the natural processes and all the potential
consequences of their interference. This is why ecological considerations can no longer be
ignored by all branches of industry connected in any way with use of natural resources of marine
and coastal environments.
5. River mouth areas
River mouths are natural systems, formed as a result of mixing of fresh and sea waters, by
interaction of different water masses and currents. They are heavily influenced by sedimentation
processes, and support peculiar freshwater-seawater ecosystems of ecotone type. Thanks to
hydrochemical regime features, and biogenic material carried by rivers, the well-warmed shallow
sea mouth areas of rivers play a unique role in productivity of marine and freshwater organisms.
The ecological importance of these areas extends over vast areas of river systems and oceans.
River mouth areas are especially vulnerable to anthropogenic load in the river basins,
particularly, to anthropogenic changes of river flow. This is partly because of the spatial
coincidence of areas of maximum aggregation of living organisms, particularly those in early
stages of ontogenesis, and maximum content of toxic substances. Anthropogenic changes in such
areas are very dangerous for biota. In recent decades, as a result of industrial activities in river
basins and construction, significant changes have occurred in aquatic ecosystems and in the
mouths of many rivers. In the Volga River delta, for example, there has been a very considerable
reduction in valuable fish resources. Exploitation of oilfields has led to further degradation of
freshwater-seawater ecosystems. Deterioration of the state of aquatic ecosystems is apparent in
the mouth areas of some of the largest rivers in the World, e.g. the Danube, Mississippi, Nile,
and Amur, Niger, Tigris, Euphrates, etc..
More than 80% of sediments enter the ocean in river flows and most of this quantity is deposited
in the mouth and near-mouth areas. The river carries the solid material (pebbles, sand, silt) to its
mouth and deposits it in calm seas. On the other hand, the sea, by wave swash, flooding and
other flows, often washes out and carries away the sediments that were deposited by the river,
and thus, acts in an opposite direction. The morphology of river mouths is largely dependent on
interaction and intensity of these antagonistic factors.
Features of the river mouth include:

stream discharge,

flow velocity,

quantity of solid material and its composition,

positive or negative Earth crust movements,

strength and direction of longshore currents and waves,

shape and orientation of the coastline, and

offshore topography.
Various combinations of these factors can explain the fact that, sometimes on the same coast,
even quite close to each other, rivers have different types of mouths. In general, we can
distinguish two main types of river mouth: 1) delta and 2) estuary. Deltas emerged as the result
of abundant sediments, transported by rivers and laid in the mouth. Estuaries are flooded by seas
lower parts of river valleys.
5.1. Deltas
Deltas are coastal and nearshore accumulative plains in the form of the Greek letter Δ. They are
primarily of fluvial origin, and are found where a stream or river discharges into a receiving
basin (ocean, sea, bay, estuary or lake). Many of the worlds largest rivers, among them the Nile,
the Volga, the Mississippi, and the Ganges have built massive deltas at their mouths. Each delta
has its own peculiarities and shape, determined by many factors.
Factors favorable for the deltas formation are: abundant sediments carried by rivers, sea
shallowness at the river mouth, absence or weakness of tidal and coastal sea currents, capable to
carry away the sediments brought by rivers. Being laid in the river mouth, the sediments are
often very thick: in the Nile delta they are more than 100 m, while in the Po delta more than 200
m. Aeolian sediments in some semidesert regions influence the deltas formation (so, in the Volga
delta such sediments are 5 cm in 100 years). Fresh waters mixed with the sea waters cause
sediments coagulation and their further sedimentation on the bottom. Usually deltas are low,
swamp and are covered by rich vegetation. Depending on the place of formation the deltas are:
outer deltas and inner deltas. Genetic classification presents complicated deltas beginning from
mono-channel to multi-channel deltas. According to contours we can distinguish cuspate, lobate
and other deltas. There are deltas classification based on energetic factor, that prevails in the
mouth offshore. When the river sediments are not abundant and the sea bottom is deep, the
incised or sculptural deltas are formed (Sea geomorphology, 1980).
Inner delta are formed when the river flows into the bay or gulf; in this case delta grows fast,
the sediments fill in the bay, protected from the waves and then enters the offshore (Neman,
Oder).
Outer delta is formed on the open coasts in the shape of convexity in the sea (Nile, Volga).
Cuspate delta is the variant of outer delta. It consists of two mouth spits and mouth territory of
the river valley. Formation of the mouth spits results from the inequality of the river flow speed
in its pivotal part (shank) and close to the banks parts. As the result, the accumulation of
sediments carried by river takes place on the extension of both banks of the river channel, while
opposite to the shank, even in the sea, the stream is still quick and prevents the accumulation
(Tiber).
Lobate delta is the variant of outer delta. It is formed in case when through each channel out of
multiple channels so many sediments are carried which waves and currents can not carry away.
That is why opposite to each channel the projection is formed. When the process is intense the
delta in a shape of bird foot is formed (Mississippi).
Sculptural (incised) delta is formed by river when the sea level lowers quickly. Channels and
arms are incised not in their own accumulative sediments, but in the ancient sediments which
form the coastal plain. They are formed when the slopes of the bottom are not steep and the solid
sediments carried by rivers are not abundant. Material accumulation takes place only within
limits of the river channels (Neva).
5.2. Estuaries
Estuaries (from the Latin aestuarium - flooded river mouth) are semi-enclosed and mostly deep
mouth areas, where a river flows directly into a sea or oceans. Normally in estuaries the lines of
equal depths (isobaths) follow the curves of the coastal line in a smoother way, forming an
entering angle. . A factor which can lead to formation of an estuary is land subsidence
(submerging) or rise of World Ocean level, as took place during the Flanders transgression.
During this process the sea intrudes into the mouth of eroded valleys, transforming them into
bays that run deep inland. Estuaries on the western coast of the Iberian peninsula (between Vigo
and Vivero Bays) and the northern coast of the Black and Azov Seas are of this origin. One of
the favorable condition for the estuary formation is previous or modern coastal submergence too.
From hydrological point of view, the boundary of estuary is the beginning of mixing of the river
and sea waters, from morphological point of view the line, where the river bed is lower than the
average sea level. Estuaries are often ly present in rivers which flow into the sea on coasts under
the influence of a large tidal range. The tide may penetrate far up the river as a wave, causing a
temporary rise of river level. During the reflux, the sea water accumulated in the river, flows
back down the river, as well as the accumulated river water, which is why the reflux flow is
stronger than the afflux. It washes out the banks, removes sediment from the river bed and
deposits them widely in the shallow waters around the mouth. Reflux flow not only prevents
accumulation of river sediments in the mouth area of rivers, but also makes the river deeper and
wider. I
Thus, estuary is geomorphological, partly erosion form. The picture of flows and mixture
process of fresh and salted waters in the estuary are very complicated, which conditions the
formation of specific estuary type of circulation. Circulation of water in estuaries is conditioned
by interaction between the river flow, sea (including tides) flows and features of water
stratification. Usually double-layer stratification is observed in estuaries, that is conditioned by
flow of fresh waters and is characterized by flows of opposite directions. In the upper layer the
flow is directed into the sea and its intensity grows together with growing of the river flow; in
the bottom layer the flow of the sea water in the coastal direction prevails and its intensity also
grows together with growing of the river flow. But growing of the river flow higher than some
specific limit lessens the intensity of the two-layer flow and the flow to the mouth begins to
prevail.
In the tidal seas maximum speeds of the bottom flow in the upper parts of estuaries are in phase
of low-tide in mouth direction. In the middle part of estuary maximum bottom speeds can be
observed in the phase of rising tide and are directed to the river; during the low-tide they are less,
but still are rather high. Maximum rising tide coincides with maximum salinity and the heavier
impact of the bottom water layer on the bottom surface of estuary. Additional complications into
the estuary circulation give vertical circulation water raising in the upper part of estuary and
sinking in the mouth part.
Estuary hydrological conditions are observed in the bays of rias, fiord, liman and lagoon types.

Rias are bays resulted of underflooding of the mountain erosion
valleys.

Fiords are sea-flooded glacial (through) valleys, initially of
tectonic or erosion origin.

Lagoons is the variant of estuary - water surfaces, separated by
bars and stretched along the coasts. Coastal bars, that are narrow,
but very long (several dozens and even hundreds of kilometers)
stripes of accumulative land, as well as lagoons are widely spread
on the coasts of the World Ocean. The reason of this phenomenon
is that modern coastal zones of seas and oceans were formed
under conditions of the Postglacial Epoch transgression of the
World Ocean, e.i. similar to the formation of the main part of
shelf. Meanwhile the vast accumulative plains composed by
alluvial, fluvial-glacial and aeolian sediments were flooded
sometimes. These sediment masses under the impact of the sea
roughness were put in motion and accumulated either on the
coast, which formed intensively growing accumulative terraces in
the form of close to each other beaches - coastal bars, which
formed as a total accumulative coastal terraces, or in some
distance in the sea, forming coastal or island bars (coastal and
island barriers). Lagoon waters differ from the sea waters by
higher (under conditions of arid climate) or lower salinity, by
stagnant hydrological regime, by high content of organic matter.
The fine silt sediments are deposited in lagoons and under high
salinity the salt deposition take place. The underwater
accumulative forms are usually formed in lagoons, connected
with impact of waves, wind and tidal flows.
Due to the absence of tides and strong wave activities in the Black and Azov seas, these water
bodies have tendency to continue eparated from the seas by spits and sandy banks, forming a
series of lagoons.

Limans the variant of estuary are formed under the sea ingression
into the river valleys, which dissect the low coastal lowlands. In
most cases such coastal plains are composed by loose rocks, that
are easily washed by the sea and from a lot of sediments. That is
why on the limans coasts there are a lot of abrasion as well as
accumulative forms, especially in their mouth. The accumulative
forms develop quickly and under favorable conditions turn into
sand banks, which separate limans from the sea and turn them
into lakes. Various phases of turning limans into lakes are
observed on the north-western coast of the Black sea, between
Odessa and Danube delta (Sea geomorphology, 1980).
6. Marine pollution
The world's estuaries and oceans are the ultimate repository for a vast array of substances
discharged deliberately or accidentally via human activities. The immediate and most acute
impacts of these activities occur in the coastal zone where population growth has increased
dramatically over the years. This growth is concentrated at the land-sea interface, and is
associated with construction of industrial installations, maintenance of harbors and other
waterways, domestic development, and other uses of coastal space. Together with pollution of
the coast zone, the risk of pollution of the open Ocean is rising. For example, open ocean waters
are subjected to frequent oil pollution by shipping (see Figure 11). In addition to pollution from
shipping operations beyond the continental shelf, the input of toxic chemicals from atmospheric
transport and deposition can also adversely affect open ocean waters. In contrast to conditions in
the open ocean, shallow estuarine and nearshore marine waters continue to be extensively
degraded by both point and non-point sources of pollution. Systems characterized by a slow rate
of exchange relative to their volume (e.g. semi-enclosed estuaries and embayments) are most
susceptible to contaminant inputs. These systems typically have a very limited assimilative
capacity for pollutants. Consequently, certain unassimilated materials, such as synthetic toxic
organic compounds, can accumulate and persist for long periods of time, posing a potential longterm danger to marine food webs.
From a global perspective, five classes of contaminants are considered to be critical to the
environmental health of the ocean (Kennish, 1997):
1. Petroleum hydrocarbons (crude oil and its refined products)
2. Halogenated hydrocarbons
3. Heavy metals (particularly mercury, cadmium, and lead)
4. Radionuclides (especially cesium-137, strontium-90, and
plutonium-239, 240)
5. Litter.
Figure 11. Areas of water pollution: 1- severely polluted areas and lakes, 2 polluted sea areas and
lakes, 3 areas of frequent oil pollution by shipping, 4 major oil tanker spills, 5 major oil rig blowout, 6 offshore dumpsites for industrial and municipal waste,
7 severely polluted rivers and estuaries.
Source: Philips Atlas of the World. Introduction to World Geography. (1997). George Philip
Limited, UK, modified.
There is evidence for a decline in concentrations of at least certain constituents of the first four
classes of these critical contaminants. The amount of litter, however, seems to be on the increase
around the world. Perhaps most alarming is the occurrence of persistent plastics which has been
on the rise in oceanic waters for a number of years.
According to M. Kennish (1997), there are three pollutant categories of priority concern today in
coastal marine environments: sewage, nutrients, and synthetic organic compounds. Sewage
input, eutrophication from excessive nutrients, and the toxic effects of persistent organic
compounds in estuaries and nearshore oceanic waters pose significant public health risks. Three
other pollutant categories (i.e. heavy metals, radionuclides, and oil) are seen as less threatening
in the sea. More general impacts of heavy metals on marine communities are evident only in the
immediate vicinity of metal-rich discharges or mine-tailing effluents, in which concentrations are
very high. Aside from nuclear accidents, marine inputs of radionuclides are now restricted to the
relatively small number of discharges from nuclear power stations and reprocessing plants.
Damage from oil pollution at sea, while potentially severe, is localized in space and time, with
the worst impacts arising from oil moving ashore and contaminating coastal wetlands, or
becoming buried in sandy beaches. The main global concern regarding oil pollution appears to
be operational discharges from large tankers, which circulate on ocean currents and affect beach
amenity far from the original source. Used oils from land-based sources may pose a potential
risk to the coastal zone worldwide. Conservative wastes (e.g. heavy metals, hydrocarbons, and
radioactivity) are potentially reactive with marine organisms and occasionally harmful to them.
7. Science and the World Ocean
The World Ocean is a complex global structure, which influences and defines the very existence
of humankind. lasting recent decades ocean science and geography have developed very well,
especially the physical aspects. Many problems of ocean science have been raised and solved,
such as dividing into the Ocean into natural zones. The nature of separate zones has been studied
in great detail. Broad studies have been done in arctic waters, from the 1920s to the present, from
both scientific ships and drifting ice. From the 1950s an ambitious program of complex research
into Arctic and Antarctic waters was initiated.
Studies of the World Ocean are typically done as large international programs. Thus, in 1986 the
International Council of Scientific Unions (ICSU) acknowledged the necessity of developing an
international program of study of the Earths Geosphere and Biosphere named "Studying the
Global Changes". Several large, long-term, international, interdisciplinary research projects are
now underway on the oceans as part of the IGBP (International Geosphere-Biosphere Program).
One example is GLOBEC (Global Ocean Ecosystem Dynamics) (Costanza, 2000).
Because of the relative vastness and inaccessibility of the oceans, their scientific exploration had,
in many senses, lagged behind the study of terrestrial systems. But in recent times, new
monitoring and remote sensing technologies have led to an explosion of new scientific
information about the oceans. Deep-sea apparatus has allowed exploration of the deepest regions
of the oceans, with the dramatic discovery of completely new life forms inhabiting deep-sea
thermal vents. Satellite remote sensing has allowed observation of the ocean surface. This has
led to discovery and mapping of important new features of ocean structure and circulation, such
as mesoscale eddies and the complex spatial patterns of marine photosynthesis. New information
has given an impulse to development of sophisticated models of the ocean system and its links to
the atmosphere and terrestrial biosphere. This activity has been stimulated by interest in the
problem of global climate change and the important role of the oceans in climate changein
particular the exchange of greenhouse gases with the atmosphere.
Questions concerning weather formation and prediction have become more and more important
in complex, multi-aspect problems of ocean and atmosphere interaction It is well known that
oceans influence the weather over vast areas of land. Ocean atmosphere interaction is
particularly active in regions where warm currents, which carry the tropical water masses, come
into comparatively cold zones and give up vast amounts of thermal energy to the environment.
These areas called energy-active ocean zones. The most important ones are situated around the
Gulf Stream, Newfoundland, in the Norwegian Sea, near Curacao and in tropical parts of oceans.
In these zones there are marked seasonal variations in surface water temperature and large
differences between water and air temperatures. For improving long-term forecasting methods in
such zones it was clear that it was necessary to organize regular perennial monitoring of the state
of ocean and atmosphere. The research includes observations made from scientific ships and use
of remote sensing. Monitoring of energy-active zones will facilitate weather forecasting and will
improve the whole global system of World Ocean monitoring.
Another significant problem connected with the ocean and atmosphere is to improve
understanding of tropical hurricanes in the Pacific Ocean, where they are known as typhoons.
The destructive force of these is well known and it is important to develop methods of reliable
prediction of the behavior of these natural processes.
The oceans contain about 85% of the global mobile carbon and act as a sink for atmospheric
carbon dioxide. Thus, the problem of climate change cannot be considered without detailed
analyses of the influence of the oceans on the carbon cycle, and carbon dioxide exchange
between ocean and atmosphere. According to some climate change scenarios, enhancement of
the greenhouse effect may cause, together with the significant temperature rise on the Earth
surface, a melting of Arctic and Antarctic glaciers sufficient to increase the World Ocean level
by 0.4 meter by 2050 (IPCC, 1996). In general, the main biogeochemical effects of sea level rise
in the coastal zone would be as follows:

inundation and displacement of wetland and lowlands;

erosion of shorelines;

exacerbation of coastal zone flooding;

alteration of tidal ranges in rivers and bays;

changes in sediment deposition patterns, and

decrease in the amount of light reaching the bottom of seas.
Unfortunately, the modeling of ocean dynamics is not yet very reliable. One problem concerned
with global climate change, which needs intense study, is maturation of the El-Nio effect.
The main features of ocean hydrochemistrymovement of principal salts, chemical exchange
between continents and ocean, and processes of sedimentation in various ocean zoneshave been
well studied. The accumulation of plankton and associated herbivores and predators at different
depths, their passage into the eutrophic (0-100m) layer during the process of convection or in the
zones of upwelling, and processes of carrying material by rivers are largely understood. At the
beginning of the twenty-first century the problems of hydrochemistry have acquired specific
significance because of marine pollution, which may affect water evaporation, gas balance, and
albedo of ocean and sea surfaces. Methods and technology for extraction of valuable resources
from ocean waters have begun, particularly for bromine, strontium, uranium, lithium, silver, and
gold.
At the end of the twentieth century humanity is faced with a severe problemdeterioration of the
health of the World Ocean. The main pollutants are oil products, heavy metals, detergents,
pesticides, and radioactive substances. In spite of water-protection measures, pollution level of
many coastal zones, according to some indices, exceeds the maximum permissible
concentrations (MPC). All oceans and many seas are facing the prospect of mineral resource
exploitation from the bottom and coastal zones. Further development of marine oil and gas
production raises many problems for researchers, as well as the need to work out technologies of
oil production under various conditions and preservation of the "purity" of the industry.
In recent decades the phenomenon of upwelling has drawn the attention of specialists,
particularly in connection with the demands of the fishery industry, as well as its influence on
water hydrochemistry, euthrophication processes, biological and fish productivity of coastal
waters, and large-scale ocean circulation. For marine biology it is typical the transition from
studying of separate marine organisms to biological communities and ecosystems as a whole,
their composition, functioning, productivity, interlinks and interactions between groups of
organisms and environment. In the oceans and seas there are vast reserves of fish and especially
invertebrates that have valuable food qualities. Vast reserves of krill, squids and some fishes in
the open ocean and in the subantarctic are almost unused. Traditionally 90% of fish and other
marketable animals are obtained from the continental shelf. Further studies have shown that in
the open ocean there are large accumulations of such animals, in pelagic waters at a depth of a
few hundred meters, over the continental slope and over underwater uplands.
A new scientific discipline has begun to develop, that of anthropogenic ocean ecology (Izrael,
Tsiban, 1992). This is the science of human impact on variability, disturbances and sustainability
of marine ecosystems. It includes learning about the assimilation capacity of marine ecosystems.
In the Russian Federation its main task now is to work out and define ecologically permissible
limits for pollution of the ecosystems of inland and marginal seas.
Social sciences also involved in study of various problems of the Ocean. So-called social
oceanology is developing successfully. This includes problems of ocean use economy (marine
transport, fisheries, oil production, production of chemical resources, recreation, etc.), socioeconomic geography and international marine law. Socio-economic geography needs to come up
with practical recommendations on rational spatial distribution of industry in the seas and
oceans, and more expedient use and management of marine resources.
Conclusions
The World Ocean is a vital life support system for human survival. Humanity has to allow its
continued exploitation in a spirit of sustainable development, and to safeguard the World Ocean
ecosystems for future generations. To develop our knowledge of the World Ocean it is necessary
to combine the efforts of many scientists from different countries. To do this several large
international programs have been organized. The role of the Ocean was recognized as central in
the International Geosphere-Biosphere Program.
Related Chapters
Click Here To View The Related Chapters
Glossary
Beach
Boundary
current
Coriolis effect
Cliff, bench
Ecosystem
Ecotone
El Nio
Euphotic layer
(photic region)
Greenhouse
effect
Hydrological
cycle
Hydrosphere
Littoral
Monsoon
Pelagic waters
:An accumulative relief form, formed in the upswash zone, an analogue of
the modern accumulative terrace.
:A current that flows generally poleward, parallel to a continental coastline.
:A phenomenon by which all moving bodies veer to the right in the northern
hemisphere and to the left in the southern hemisphere.
:An abrasion relief form in the upswash zone, an analogue of the modern
abrasion terrace.
:The otality of living organisms (a trophic pyramid) in their environment and
their interactions.
:A transitional zone, which forms at the border of different ecosystems,
natural zones or environmental conditions (atmosphere-land, land-ocean,
fresh water marine water, etc.).
:A periodic climatic variation in which trade winds slacken and surface
waters of the central and eastern Pacific become anomalously warm.
:The surface ocean zone in which enough solar light penetrates for
photosynthesis to occur. The lower border of the euphotic layer is the depth
at which the degree of illumination is 1% of the illumination at the ocean
surface. Its average depth is 80 m. It is opposite to the aphotic zone.
:The property of the Earths atmosphere by which long wavelength heat rays
from the Earths surface are trapped or reflected back by the atmosphere.
:A recurrence of different forms of movement of water and changes of its
physical state in nature on a given area of the Earth (a river or lake basin, a
sea, a continent, Earths land, the World Ocean, or the entire Earth).
:The totality of the Earths water, including oceans, lakes, streams, soil and
underground waters.
:The bottom belt, that is dry during the low water period and developing as
beach under the impact of not only sea, but sub-aeration factors as well.
:A seasonal wind accompanying temperature changes over land and water
from one season of the year to another.
:A thick layer of ocean, sea or lake waters as a sphere of habitation for life
forms (plankton, nekton, pleuston). It is opposite to benthal, i.e. the bottom of
a water body inhabited by benthos.
:An ocean zone beneath the surface zone in which water density increases
rapidly, as a result of a decrease in temperature, increase in salinity, or both.
Spreading of the :a process of moving apart of solid lithosphere platforms in the regions of
rifts of the mid-ocean ridges with constant renewal of the Earths crust (of
oceans bottom
oceanic type) from material of the upper mantle heated by upward
convectional drifts.
:A rise of water level relative to the land so that areas formerly dry are
Submergence
inundated.
:Rapidly decreasing temperature with depth.
Thermocline
:The rhythmic, twice-daily rise and fall of ocean waters, caused by
Tides
gravitational attraction between the Moon (and to a lesser degree, the Sun)
and the Earth.
:A violent whirl of destructive winds which nearly always is accompanied by
Tornado
a funnel cloud hanging down from a cumulonimbus clouds. The diameter of
tornado is usually a few hundred meters, and the maximum wind is in excess
of 100 mph. Passing on the earth or water surface tornado takes up a column of
Pycnocline
dust, sand and water. It has especially fast rotator and forward movement with a
great destructive force. Accompanied often by rainstorm.
Thunderstorm
Trade winds
Upwelling
Water mass
:A relatively small storm involving one or more cumulonimbus clouds,
always accompanied by lightning and thunder, generally with rain and gusty
winds, and sometimes with hail.
:The winds that occupy most of the tropics and blow from the subtropical
highs toward the equatorial trough; they are mostly northeasterly in the
northern hemisphere and southeasterly in the southern hemisphere.
:The process by which subsurface waters flow upward and replace the water
that is moving away. In the coastal sea zone this process is caused by winds
from the coast, that draw the surface water into the open sea.
:A water volume, formed under concrete physical-geographical conditions
and possessing comparable homogeneity of physical-chemical characteristics.
Bibliography
Fundamental Soviet Encyclopedia (1979). Moscow, BSE.
Costanza R., (2000). The Ecological, Economic, and Social Importance of the Oceans. Seas at the Millennium: An
Environmental Evaluation (Edited by C. Sheppard). Elsevier Sciences Ltd.
IPCC. (1996). Climate change 1995: The Science of Climate Change. Contribution of Working Group II to the
Second Assessment Report of the Intergovernmental Panel of Climate Change. Cambridge University Press,
Cambridge, 586 p.
International Petroleum Encyclopedia (2001) Penn Well, USA, Vol. 34.
Izrael Yu. , Tsiban A.B., (1992). Anthropogenic ecology of ocean, Moscow, Nauka. (in Russian).
Handbook of Applied Hydrology (1960) Ed. By Ven Te Chow, McGRAW HILL BOOK COMPANY, New-York San Francisco Toronto London. p.
Kennish M.J. (1997). Practical Handbook of Estuarine and Marine Pollution. CRC Press Marine Science Series.
Kuusisto E,. Lemmela R., Liebscher H., & Nobilis F. (1997). Climate and Water in Europe: Water Quality and
Aquatic Ecosystems. WMO.
Longinov, V.V. (1966). Lythodynamics of coastal zone on the tideless seas, Leningrad, Nauka, (In Russ.).
Mee L. (1992). The Black Sea in crisis: a need for concerted international action. Ambio 21, pp. 278-286.
Philips Atlas of the World. Introduction to World Geography. (1997). George Philip Limited, UK.
Sea geomorphology, (1980). Terminology reference book. Moscow: Nauka. (In Russian).
Semptner, A, (1995). Modeling ocean circulation. Science 269, pp, 1379-1386.
Schukin I.S. (1974). General geomorphology. V.3. MSU Pub. House. (in Russian).
Skinner B.J., & S.C. Porter, (1994). The Blue Planet. An Introduction to Earth System Science. John Wiley &Sons,
Inc., USA.
Strahler А. N. (1960). Physical Geography, 2d ed., copyright 1960 by John Wiley & Sons, Inc
U.S. Department of the Interior Minerals Management Service. Gulf of Mexico OCS Oil and Gas Lease Sales:
2003-2007, (2002). Final Environmental Impact Statement. Vol. 1. Published by U.S. Department of the Interior
Minerals Management Service, Gulf of Mexico OCS Region, New Orleans, LA, (ММS, 2002).
Biographical Sketch
Natalia N. Mitina graduated from the Geographical Faculty, Moscow State University in 1977. She received her
Candidate of Sciences degree (equivalent to Ph.D.) in submerged landscapes of the Sea of Japan in 1994 at StPetersburg State University and Doctor Degree in 2005. Since 1996 she has held a position of Senior Research
Scientist at the Institute of Water Problems Russian Academy of Sciences in Moscow. Natalia N. Mitina is a Senior
Fulbright Scholar of 2002-2003. She is the author of more then 80 scientific publications. Her research interests are
in the fields of conceptual methodologies of formation and classification of subaquatic landscapes, and their stability
and transformation as a result of natural processes and anthropogenic load. She is dealing now with estimation of
anthropogenic load on river mouth natural complexes and recommendations for their protection. Her main
publications are: Mitina N.N. Geoecological investigations of the subaquatic shallow-water landscapes. M, Nauka,
2005, 200 p. (in Russian) Mitina N.N. "The dynamics of main landscape forming factors of river mouth regions
under different anthropogenic load", 2002, Surface Water Hydrology. A.A. Balkema Publishers
Lisse/Abingdon/Exton (pa)/Tokyo, Edited by V.P. Singh, M. Al-Rashed, M.M., Sheriff, Vol. 1, pp.451-456.
Puzachenko Yu. G., Mitina N.N. "Marine Communities" State and Protection of Biological and Landscape Diversity
for the Caspian Region. National Report. Part 2.1. Moscow, Ministry of Natural Resources for Russian Federation.
2000. Pp. 39-79. Mitina N.N. "Estimation of the Natural Aqua-complexes Sensibility to Potential Climate
Fluctuations in the Coastal Zone of the Sea of Japan". Proc. 2-nd Int. Conf. on Climate and Water. Espoo, Finland
17-20 August, 1998,Vol. 2, pp. 605-614. Mitina N.N. The Significance of the Mouths of Small Rivers for the
Preservation of Aquatic Ecosystem. British Hydrological Society Occasional Paper, UK, 1998, No. 9, pp. 54-59.
To cite this chapter
N.N. Mitina, (2006), PROPERTIES OF OCEANS, INLAND SEAS, COASTAL ZONES, AND ESTUARIES, in
Types and Properties of Waters, [Ed. Martin G. Khublaryan], in Encyclopedia of Life Support Systems (EOLSS),
Developed under the Auspices of the UNESCO, Eolss Publishers, Oxford ,UK, [http://www.eolss.net] [Retrieved
September 5, 2007]
©UNESCO-EOLSS
Encyclopedia of Life Support Systems