Physical and Geological

processes in the Oceans

AQ 233

Lecture 1

SCOPE OF THE COURSE1. Introduction to Oceanography

2. General features of the oceans

3. Physical properties of seawater

4. Ocean circulation

5. Waves, Tides and Tsunami

6. Coastal Features (Beaches, estuaries and deltas)

7. Special topics: El Nino & Hurricanes

METHODS OF ASSESSMENT

• Practicals

• Quiz

• One mid-course test

• Final examination

Some Preference books for physical oceanography and

marine sciences in general

• Pickard, G.L., and Emery, W.J. (1990). Descriptive Physical Oceanography. An introduction, (5th Edition). Pergamon Press, Oxford, UK

• Gross, M.G. (1972). Oceanography, a view of the earth. Prentice-Hall, Englewood Cliffs

• Ross, M.A. (1995). Introduction to Oceanography. Harper Collins New York

• Pond, S. and Pickard, G.L. (1983), Introductory Dynamical Oceanography. 2nd Edition. Pergamon Press, Oxford, UK

• Bowden, K.F. (1983) Physical Oceanography for Coastal Waters. Ellis Horwood Limited, England. pp. 302

• Prager, E.J. and Earle, S.A. 2000. The Oceans. McGraw Hill. pp. 314

• Thurman, H.V. and Trujillo, A.P. 2004. Introductory Oceanography. Tenth Edition. Person-Prentice Hall. New Jersey.

• Websites

Focus of the first Lecture▪ Earth’s compartments: the Earth could be divided into

four main compartments

▪ Why study oceans

▪ What is Oceanography

▪ What is Physical Oceanography

▪ Oceans of the World

▪ Structure of Ocean floor

Earth’s compartments

Water in the Biosphere

Volume (Thousands

of km3)

% of the Total

Oceans 1,370,000 97.2

Glaciers 29,000 2.1

Groundwater 4,000 0.62

Freshwater

lakes

125 0.009

Saline lakes 104 0.008

Soil moisture 67 0.005

Rivers 1.2 0.00009

Atmosphere 14 0.0009

Why study the oceans• The oceans is a continuous body of salt water.

• The ocean is a fluid in turbulent motion

• The oceans cover about 71% of the surface of the earth and land covers the remaining 29 %.

• The ocean affects many aspects of our environment, such as climate, weather and sea level.

• The oceans do not operate alone but together with the atmosphere, continents and ice-cover, they form a working machine, driven mostly by energy from the sun. Lesser amounts of energy derive from tides raised by the moon and sun and planets, and heat from the Earth’s interior.

• Oceans are an important source of food, energy, minerals, chemical, recreational and transportation resources.

08/04/2019

Role of ocean in regulating climate

• It stores most of the sun energy

• It transport heat around the globe, pumping warm water and air toward the poles, and cold water and air back to the tropics

• It regulates wind and precipitation patterns, such as cloud formation (evaporation), cloud movement (wind) and rain/snow formation (condensation)

• It controls freezing and thawing in polar regions through the sea ice formation/shrink

• It acts as a reservoir of carbon, soaking up carbon dioxide from the atmosphere

Ocean plays an important role in interaction with the atmosphere

Picture from Ocean Motion, NASA

What is Oceanography (marine

science)• is a scientific study of the ocean

• is the application of all disciplines and methods of science to understanding ocean phenomena.

• Oceanography is the science that studies the world's oceans, its waters and depths, how they move and how they play a part in the whole of our planet.

• Oceanography is the study of the deep sea and shallow coastal oceans: their biology, chemistry, geology and physics.

• Oceanography is not a single pure science but a combination of several.

ASTRONOMYTidal forces

GEOLOGYSea floor

tectonics, coastal

processes, sediments,

hydrologic cycles

PHYSICSThermal

properties of

water, sonar,

waves, currents

CHEMISTRYDissolved components,

temperature

dependence,

stratification/density,

chemical tracers

BIOLOGYFisheries, marine

adaptations

GEOGRAPHYWind belts,

weather,

coastal landforms,

World climate

OCEANOGRAPHY

An Interdisciplinary Science

What is Physical oceanography

• the physical characteristics of the water in the ocean,

such as the motion of the water from the molecular

level to the global scale, including ocean currents,

eddies, waves, and tides. Interaction of the ocean

with the atmosphere is another important area of

inquiry.

• studies all forms of motion in the ocean.

• Synoptic Oceanograpy– Observation, preparation

and interpretation of oceanographic data

• Dynamic Oceanography – applies the laws of physics

to ocean, regarding it as a fluid acted upon by forces

and solve the resulting mathematical equations

Branches of Physical Oceanography

Distribution of water on the Earth’s surface

Atlantic Ocean 25%

Indian Ocean 20%

Pacific Ocean 52%

Ice 2%

Atmosphere, lakes and

rivers

0.01%

Ground water 0.625%

Ocean of the world

• The three major bodies of water: the Atlantic, Indian

and Pacific Oceans

• The Pacific Ocean, the largest and deepest,

constitutes about 43% of the oceanic area of the

world, and is larger than all land areas combined.

Also having both a surface area and a volume

greater than the other oceans combined

• The Southern Hemisphere is dominated by ocean

(80.9%) because of the connection of the ocean

basins around Antarctica. Although the northern

hemisphere contain most of the land, it is still

dominated by ocean (60.7%)

Oceans of the world

Different characteristics of major

oceans

• Indian Ocean is the smallest, youngest, and physically most complex of the world’s three major oceans.

• Indian Ocean has the fewest marginal seas of the major oceans

• In the Northern Hemisphere it is landlocked and does not extend to Arctic waters

• It has fewer islands and narrower continental shelves.

• It is the only ocean with an asymmetric and, in the north, semiannually reversing surface circulation.

• The Atlantic is relatively narrow and has by far the largest drainage area.

Oceans of the world

What is the difference between oceans and

seas?

Smaller water bodies• Sea: Is also a portion of an ocean which is not divided

off by land but has local distinguishing oceanographic characteristics

• Mediterranean Sea, Caribbean Sea, Sea of Japan, Bering Sea, Norwegian Sea; Labrador Sea; Tasman Sea, etc

These are bounded by land or by island chains

Have restricted connections with ocean and thus, have restricted exchange of water with open ocean

• Average depth of oceans – 3 700m

• Average depth of seas - 1200 m

Provinces of the ocean floor

• The major oceans are structured into:

i) Continental margins – shallow-water areas

close to continents

ii) Ocean basins – deep-water areas farther from

land and Mid- ocean ridges, which are

shallower areas near the middle of an ocean

Structure of sea floor

Continental margins

• Continental shelf – flat zone extending from the

shore beneath the ocean surface to a point at

which a marked increase in slope angle occurs,

called the shelf break.

• Usually flat and relatively featureless because

of marine sediment deposits but can contain

coastal islands, reefs and raised banks

• Underlying rock is granitic continental crust – so

geologically part of continent

• The average width of the continental shelf is

about 70 km

Continental margins

• Continental slope – lies beyond the shelf break.

Total relief is similar to that found in mountain

ranges on the continents

• Continental Rise – is a transition zone between

the continental margin and the deep ocean floor

comprised of a huge submerged pile of debris

• Features of the ocean basin – Abyssal plains,

seamounts and trenches, and the Mid-ocean

ridge

Topography of the ocean floor – Hypsographic

Curve• Hypsographic Curve-shows the relationship between height of

the land and the depth of the oceans. It shows amount of Earth’s surface above or below any selected elevation or depth

• In the past, the ocean bottom was considered to be a smooth

• bi-modal distribution in the elevation distribution. It is apparent that most of the earth's surface is covered by deep basins and low lying land

• The frequency plot shows that only about 29% of the Earth’s crust projects above the sea level. This means that we humans inhabit and know most about the area of the Earth that is unrepresentative of its surface, the dry land! These data also reveal that mountains and deep-sea trenches are uncommon landforms

• The average depth of the ocean is about 3.7 km and the deepest areas, in the Marianas and Philippine trenches, are over 11 km deep.

• Average height of the land is 840 m and the highest point is 8850 meter – Mt Everest

Frequency distribution of land and sea

Hypsographic Curve

• The curve shows five different sloped

segments:

i) Tall mountains – steep slope

ii) Low coastal plains – gentle slope

iii) Continental margins – steep areas

iv) Deep-ocean basin – longest and flattest part

v) Ocean trenches – steep slope