Oceanography and coastal zone policy

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Presentation Topic: Oceanography and
Coastal Zone Policy of Bangladesh
Presented by Group-01

Oceanography is the study of the physical, chemical, and
biological features of the ocean, including the ocean’s ancient
history, its current condition, and its future.
It is known as Oceanology.
It is an Earth science covering a wide range of topics, including
ecosystem dynamics, ocean currents, waves, and geophysical fluid
dynamics, plate tectonics and the geology of the sea floor, and
fluxes of various chemical substances and physical properties
within the ocean and across its boundaries.
Definition of Oceanogrphy

Oceanic crust is the outermost layer of earth’s lithosphere that is
found under the oceans and formed at spreading centers on
oceanic ridges, which occur at divergent plate boundaries.
It is about 6 km thick and composed of several layers, not including
the overlying sediment.
The topmost layer, about 500 meters thick, includes lavas made of
basalt.
Oceanic crust differs from continental crust in several ways: it is
thinner, denser, younger, and of different chemical composition.
Like continental crust, however, oceanic crust is destroyed in
subduction zones.
Oceanic Crust-

Oceanic basin is any of several vast submarine regions that
collectively cover nearly three-quarters of Earth’s surface. Together
they contain the overwhelming majority of all water on the planet.
Geologically, they are large basin below the sea level.
It has an average depth of almost 4 km (about 2.5 miles) from the
sea level.
Oceanic Basin-

In hydrology, an oceanic basin may be anywhere on Earth that is covered by
seawater, but geologically ocean basins are below sea level. Geologically, there are
other undersea geomorphologic features such as the continental shelves, the deep
ocean trenches, and the undersea mountain ranges, which are not considered to be
part of the ocean basins; while hydrologically, oceanic basins include Older
references consider the oceanic basins to be the complement to the continents, with
erosion dominating the latter, and the sediments so derived ending up in the ocean
basins.
Geologically, an oceanic basin may be actively changing size or may be relatively,
tectonically inactive, depending on whether there is a moving plate tectonic
boundary associated with it. The elements of an active - and growing - oceanic basin
include an elevated mid-ocean ridge, flanking abyssal hills leading down to abyssal
plains. The elements of an active oceanic basin often include the oceanic trench
associated with a subduction zone.
Origin and Permanency of Oceanic Basin

Through most of geologic time, probably extending back 2 billion years, the ocean
basins have both grown and been consumed as plate tectonics continued on Earth.
The latest phase of ocean basin growth began just less than 200 million years ago
with the breakup of the supercontinent Pangaea, the enormous landmass
composed of nearly all the present-day continents. Since that time the major
developments have included a shrinking of the Pacific basin at the expense of the
growing Atlantic and Arctic basins, the opening of the Tethys seaway circling the
globe in tropical latitudes and its subsequent closing, and the opening of the
Southern Ocean as the southern continents moved north away fromAntarctica.
Origin and Permanency of Oceanic Basin

The oldest known oceanic crust is located in the far western equatorial Pacific,
east of the Mariana Island arc.
The Pacific ocean floor at this site was generated during seafloor spreading from a
pattern of ridges and plates that had existed for some unknown period of time. At
least five different seafloor spreading centers were involved.
In the Indian Ocean the oldest segment of seafloor was formed about 165 to 145
million years ago by the rifting away of Africa and South America from Gondwana,
a supercontinent consisting largely of the present-day continents of the Southern
Hemisphere.
At this time Africa was joined to South America, Eurasia, and North America.
Today this old seafloor is found along the east coast of Africa from the Somali Basin
to the east coast of South Africa and adjacent to Queen Maud Land and Enderby
Land in East Antarctica.

Between 90 and 80 million years ago, Madagascar and India separated, and the
spreading ridges in the Indian Ocean were reorganized. India began drifting
northward directly toward Asia.
During this same period, Europe, joined to Greenland, began drifting away from
North America, which resulted in the emergence of the seafloor in the Labrador
Sea and the northernmostAtlantic Ocean.
This spreading phase affected the passages in the Tethys seaway between
Europe (Iberia) and northwest Africa, intermittently opening and closing it. In the
southwest Pacific, New Zealand, along with the Lord Howe Rise and the Norfolk
Ridge, rifted away from Australia and Antarctica between 80 and 60 million years
ago, opening theTasman Sea.

The properties of pure water are unique in comparison with those of other liquids,
and the nature of our physical environment—that is, the characteristics of the
oceans, the atmosphere, and the land—is in many ways dependent upon the
peculiar properties of water.
The “fitness” of water for the manifold needs of living organisms has been pointed
out by physiologists and ecologists (for example, Henderson, 1913, Bayliss, 1927).
The unique character of water is further emphasized by the fact that, according to
studies on related compounds, pure water should freeze at about − 0°C and boil at
− 100°C. The chemical constitution of water offers no explanation for these
anomalies and certain other deviations from the theoretical properties.
However, it has been found that liquid water is not made up of individual H2O
molecules but that it is polymerized—that is, multiple groups containing one, two,
or three elementary H2O molecules may exist. These are referred to as
monohydrol, dihydrol, and trihydrol.
Ocean Water- Physical Parameters:

The discovery of isotopes of hydrogen and oxygen has modified our conception
of “pure” water. All naturally occurring water contains small but variable amounts
of heavy hydrogen (deuterium) and heavy oxygen.
The amounts of the heavy isotopes vary somewhat, depending upon the source
of the water.
In 1935 Wirth, Thompson, and Utterback found that distilled water prepared from
sea-water samples was, on the average, 1.4 × 10−6 greater in density than
distilled tap water. Sea water from areas of great dilution showed a somewhat
smaller anomaly—namely, 0.2 to 0.5 × 10−6 in density. Samples from the depths
of the ocean were higher than the average.

Again in 1939 Swartout and Dole found that the density of water distilled from a
sea-water sample was 1.7 × 10−6 greater than that prepared from Lake Michigan
water. They also found that the ratio between hydrogen and deuterium in sea
water was about 7000:1.
Rain water and consequently fresh water has a lower proportion of the heavy
isotopes than sea water, since a certain fractionation takes place in the process of
evaporation. The field of isotope study is relatively new, and as yet little is known
about the distribution or significance of the isotopes. Their variability is
apparently rather small and consequently will not significantly affect the
magnitude of the properties to be discussed.

Air- Sea Interactions
The oceans and atmosphere interact in many different ways. There can be a net
exchange of heat, salt, water and momentum between them.
When wind blows over the ocean, energy is transferred from the wind to the ocean
currents. Water can evaporate more easily into warm air, especially if it is windy. As it
evaporates, it removes heat from the ocean. If it then condenses to form a cloud
droplet, it releases the heat into the air. This is one of the main ways they get their
energy.
Salt is continuously brought into the oceans by the rivers draining off the
continents, which carry minerals dissolved from the rocks they run over, and
deposited as sediment on the ocean floor. On the other hand rain dilutes the salt
concentration of the surface ocean. In addition, when it’s really windy, salty droplets
of ocean water can be blown into the air, and these can form the basis of cloud
droplets.

Air- Sea Interactions
The air and the ocean are continuously exchanging heat. As the ocean has a
higher heat capacity, it takes longer to adjust to changes in incoming radiation,
and therefore tends to change temperature slower. It means the surface of the sea
is usually a different temperature to the air immediately above it, and heat is
transferred between the ocean and the atmosphere.
There are many feedback mechanisms between the oceans and the atmospheres.
For example, evaporating water can condense in the atmosphere to form clouds.
These reflect both incoming and outgoing radiation and so determine the
temperature of the ocean surface.

Ocean Circulation
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Ocean circulation is the large scale movement of waters in
the ocean basins. It is a continuous, directed movement of
seawater generated by forces acting upon this mean flow.
Ocean circulation is a key regulator of climate by storing and
transporting heat, carbon, nutrients and freshwater all
around the world .

How Does Ocean Circulation occur?
Surface circulation carries the warm upper waters poleward from the tropics.
Heat is disbursed along the way from the waters to the atmosphere. At the poles,
the water is further cooled during winter, and sinks to the deep ocean. This is
especially true in the North Atlantic and along Antarctica. Deep ocean water
gradually returns to the surface nearly everywhere in the ocean. Once at the
surface it is carried back to the tropics, and the cycle begins again. The more
efficient the cycle, the more heat is transferred, and the warmer the climate.
Due to the rotation of the earth, currents are deflected to the right in the
northern hemisphere and to the left in the southern hemisphere. This effect is
known as the "Coriolis force." The deflection leads to highs and lows of sea level
directly proportional to the speed of the surface currents.
15

How Does Ocean Circulation Occur
Variations in the ocean's circulation can lead to variations in heat transport
and to variations in weather patterns. One important variation in the
circulation is the change in the equatorial circulation known as El Niño which
occurs with an irregular period of two to five years.
Figure: Ocean Circulation 16

Factors Affecting Ocean Circulation
There are six major factors which is responsible for ocean circulation.
• The Rotation of the Earth:The rotation of the Earth, which affects the direction of
movement, deflects poleward current eastwards, equator wards currents
westwards. It may be pointed out here that the wind induced surface current
deflects 45° or less from the wind direction so that the deflection of ocean
circulation are much more than the deflection of wind caused by Earth’s rotation.
• Wind:Wind is the single biggest factor in the creation of surface circulation. Strong
winds moving across an expanse of water move the surface of the water. These
strong winds are not random breezes; the major winds that most often effect the
creation of ocean circulation are the Westerlies, which blow west to east, and the
TradeWinds, which blow east to west.
17

• Water Density: Another major factor in the creation of circulation is water
density, caused by the amount of salt in a body of water, and its temperature.
Water with a higher salinity, or colder water, is more dense and likely to sink.
Sinking water pushes the water below it up. The combination of sinking and rising
in the same area causes a circulation.
• Ocean Bottom Topography: Water contours to the topography of the ocean floor
or bed. If the ocean bottom "drops out," like in a valley or trench, the moving
water will move downward. If there is a rise in the ocean bottom, like a ridge or
mountain, the water moving along it will be forced upward. The sudden upward or
downward change of direction causes water displacement, creating a circulation.
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• Coriolis Effect: When a rotating object collides with another moving or stationery
force, it creates a new motion. The Earth's rotation creates two circulation: one, a
clockwise movement of water in the Northern Hemisphere; the other, a counter-
clockwise movement of water in the Southern hemisphere. When these circulation
are deflected by land masses, they create huge ocean circulation called gyres.
• The Shape of the Coastline: The shape of the coastline of the ocean basins often
deflects currents from their direct courses.
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EL NINO
El Nino is a climate pattern that describes the unusual warming of surface waters
in the eastern Pacific Ocean.
 El Nino is the “warm phase” of a larger phenomenon called the El Nino-Southern
Oscillation (ENSO). La Nina, the “cool phase” of ENSO, is a pattern that describes
the unusual cooling of the region’s surface waters.
El Niño has an impact on ocean temperatures, the speed and strength of
ocean currents, the health of coastal fisheries, and local weather from Australia to
SouthAmerica and beyond.
El Niño events occur irregularly at two- to seven-year intervals. However, El Niño
is not a regular cycle, or predictable in the sense that ocean tides are.
20

What happen during an El-Nino?
21
During an El Niño event, the surface waters in the central
and eastern Pacific Ocean become significantly warmer than
usual. That change is intimately tied to the atmosphere and
to the winds blowing over the vast Pacific. Easterly trade
winds (which blow from the Americas toward Asia) falter and
can even turn around into westerlies. This allows great
masses of warm water to slosh from the western Pacific
toward the Americas. It also reduces the upwelling of cooler,
nutrient-rich waters from the deep—shutting down or
reversing ocean currents along the equator and along the
west coast of South and Central America.

What happen during an El-Nino?
22
The circulation of the air above the tropical Pacific Ocean responds to
this tremendous redistribution of ocean heat. The typically strong high-
pressure systems of the eastern Pacific weaken, thus changing the
balance of atmospheric pressure across the eastern, central, and
western Pacific. While easterly winds tend to be dry and steady, Pacific
westerlies tend to come in bursts of warmer, moister air.

Ocean Dynamics ofWind Waves,Tides, Currents
Ocean dynamics define and describe the motion of water within the oceans. Ocean
temperature and motion fields can be separated into three distinct layers: mixed
(surface) layer, upper ocean (above the thermocline), and deep ocean.
Dynamic of Wind Waves
In fluid dynamics, wind waves, or wind-generated waves, are surface waves that
occur on the free surface of bodies of water (like oceans, seas, lakes, rivers,
canals, puddles or ponds). They result from the wind blowing over an area of fluid
surface. Waves in the oceans can travel thousands of miles before reaching land.
Wind waves on Earth range in size from small ripples, to waves over 100 ft (30 m)
high.
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Dynamic of Wind Waves
When directly generated and affected by local winds, a wind wave system is called a
wind sea. After the wind ceases to blow, wind waves are called swells. More generally, a
swell consists of wind-generated waves that are not significantly affected by the local
wind at that time. They have been generated elsewhere or some time ago. Wind waves
in the ocean are called ocean surface waves.
Wind waves have a certain amount of randomness: subsequent waves differ in height,
duration, and shape with limited predictability. They can be described as a stochastic
process, in combination with the physics governing their generation, growth,
propagation and decay—as well as governing the interdependence between flow
quantities such as: the water surface movements, flow velocities and water pressure.
The key statistics of wind waves (both seas and swells) in evolving sea states can be
predicted with wind wave models.
Although waves are usually considered in the water seas of Earth, the hydrocarbon seas
ofTitan may also have wind-driven waves.
24

Dynamic ofTides
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational
forces exerted by the Moon and the Sun and the rotation of Earth.
The times and amplitude of tides at any given locale are influenced by the alignment of
the Sun and Moon, by the pattern of tides in the deep ocean, by the amphidromic systems
of the oceans, and the shape of the coastline and near-shore bathymetry. Some shorelines
experience a semi-diurnal tide—two nearly equal high and low tides each day. Other
locations experience a diurnal tide—only one high and low tide each day. A "mixed tide"—
two uneven tides a day, or one high and one low—is also possible.
25

Dynamic ofTides
Tides vary on timescales ranging from hours to years due to a number of factors.
To make accurate records, tide gauges at fixed stations measure water level over
time. Gauges ignore variations caused by waves with periods shorter than
minutes. These data are compared to the reference (or datum) level usually called
mean sea level.
While tides are usually the largest source of short-term sea-level fluctuations,
sea levels are also subject to forces such as wind and barometric pressure
changes, resulting in storm surges, especially in shallow seas and near coasts.
Tidal phenomena are not limited to the oceans, but can occur in other systems
whenever a gravitational field that varies in time and space is present. For
example, the solid part of the Earth is affected by tides, though this is not as
easily seen as the water tidal movements. 26

Dynamic of Currents
An ocean current is a continuous, directed movement of seawater generated by forces
acting upon this mean flow, such as breaking waves, wind, the Coriolis Effect, caballing,
temperature and salinity differences, while tides are caused by the gravitational pull of
the Sun and Moon. Depth contours, shoreline configurations, and interactions with other
currents influence a current's direction and strength. Therefore, ocean currents are
primarily horizontal water movements.
Ocean currents flow for great distances, and together, create the global conveyor belt
which plays a dominant role in determining the climate of many of the Earth’s regions.
More specifically, ocean currents influence the temperature of the regions through which
they travel. For example, warm currents traveling along more temperate coasts increase
the temperature of the area by warming the sea breezes that blow over them. Perhaps
the most striking example is the Gulf Stream, which makes northwest Europe much more
temperate. 27

Dynamic of Currents
Surface oceanic currents are sometimes wind driven and develop their typical
clockwise spirals in the northern hemisphere and counter-clockwise rotation in the
southern hemisphere due to imposed wind stresses. In these wind driven currents,
the Ekman spiral effect results in the currents flowing at an angle to the driving
winds. In addition, the areas of surface ocean currents move somewhat with the
seasons; this is most notable in equatorial currents
Surface currents make up only 8% of all water in the ocean, are generally
restricted to the upper 400 m (1,300 ft) of ocean water, and are separated from
lower regions by varying temperatures and salinity which affect the density of the
water, which in turn, defines each oceanic region. Because the movement of deep
water in ocean basins is caused by density driven forces and gravity, deep waters
sink into deep ocean basins at high latitudes where the temperatures are cold
enough to cause the density to increase.
28

Coastal Zone Policy (2005)
The CZPo initiates a process that commits different Ministries, Departments and
Agencies to agree to harmonize and coordinate their activities in the coastal zone
and elaborates the basis for a firm co-ordination mechanism.
Coastal Setting:The coast of Bangladesh is known as the Zone ofVulnerabilities
as it is prone to different natural disasters at most of the time of the year. On the
other hand, it is a great source of different valuable natural resources and contains
several ecosystems. So for the present situation of the country including-
increasing population, competition for limited resources, lack of economic
opportunities, important ecological hotspots etc calls for distinctive coastal
management and the Government also realizes the need and formulated these
coastal zone policies.
29

ICZM: Key to Coastal Development: The main principles in ICZM
includes:
• A. integration through harmony and coordination.
• B. priority setting on issues of the coastal zone.
• C. co-management and participatory decisions.
• D. participatory monitoring and evaluation.
• E. gender equality.
• F. linkage to national planning mechanisms.
30
Coastal Zone Policy (2005)

31
The Government has made the coastal zone policy to provide general
guidance so that the coastal people can pursue their livelihoods under
secured conditions in a sustainable manner without impairing the
integrity of the natural environment.
1. Economic Growth:
a. Efforts will be made to enhance annual growth rate to a level to achieve
national goal for poverty and economic growth.
b.The sea beaches of the country and the Sundarban will be further
developed to attract tourists, leading to the economic growth of the country.
c. steps will be taken for medium and small private investments for coastal
development and coastal resources management.
Policy Framework:

32
2. Basic Needs and Opportunities for Livelihoods:
a. Creation of Job Opportunities.
b. Special Measures must be taken during the disaster period.
c. An integrated network of communication including highways, major
roads, railways and waterways will be developed.
d. Khash Land will be distributed among the landless.
e. No stopage of an existing employment shall be made without
creating opportunities for alternative employment.
Policy Framework:

33
3. Sustainable Management of natural resources:
a. Sustainable use of renewable and renewable resources.
b. Participation of people in all sectors and development of social
awareness.
c. Land: Planning will be done under land use policy to control unplanned
and indiscriminate use of land resources.
d.Water: Sustainable use and management of groundwater. Rainwater
harvesting and conservation shall be promoted. Small water reservoirs shall
be built to capture tidal water to enhance minor irrigation in coastal areas.
e. Aquaculture: Environmentally adopted and socially responsive shrimp
farming will be encouraged. Crab culture, pearl culture and sea grass will also
be encouraged and thus help ion the economic growth and development of
the country.
Policy Framework:

34
4. Reduction ofVulnerabilities:
a. Effective measures will be taken to enhance coping capacity of the
poor during different disaster periods in the coastal areas.
b. Sea-dykes will be regularly maintained as first line of defense and
enhancing afforestation to cope with different disasters.
c. Special care for children, women, the disabled and the old during
disaster and post-disaster period.
d. Adequate provision will be made for safety of livestock during the
time of different coastal hazards and disasters.
Policy Framework:

Oceanography and coastal zone policy

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