The characteristics of marine environment

by Aaron Finch

The sea is one of the most important environments on Earth, both because it covers more than two-thirds of the planet’s surface and because all life on land (or in freshwater) is ultimately dependent on what goes on in this alien world.

The ocean is the planet’s largest habitat

 It can be seen from space as a vast, uniformly colored blue expanse, but in fact it is divided into distinct zones or regions with radically different physical and biological properties.

Oceanographers divide the ocean into seven seas: The Pacific Ocean, the Atlantic Ocean. 

The Indian Ocean, the Southern Ocean, the Arctic Ocean and two minor seas—the Mediterranean Sea and the Red Sea. Among these seven seas, the Pacific ocean is the largest in area (about 60% of Earth’s water surface), followed by the Atlantic ocean (about 20%), Indian ocean (about 14%) and Arctic ocean(about 10%).

The major divisions of marine waters are shown in figure below.

1. The Pacific Ocean

It is the world’s largest ocean, covering approximately 30% of the Earth’s surface. It separates Asia and Australia from the Americas, and contains the seas which are situated between Asia and North America on one side and North America and South America on the other. 

The Pacific Ocean is bounded by Asia in the East, by Australia in the south-east, by Antarctica in south (and partially by Atlantic ocean),by Americans in north(partially)and by a chain of islands known as Micronesia (which includes Marianas, Carolinas etc) in NW.

The coastline of this ocean along with those oceans is roughly 115000 km long. It was named Pacific because of the peaceful nature of its waters.

The Pacific Ocean has a high water and weather variability, thus the climate is tropical in most of the ocean with some temperate regions near coastal areas. 

The water temperature varies from 30°C to 14°C along the equator.

2. The Atlantic Ocean

It is the second largest ocean in terms of area (28%) after the Pacific ocean and covers approximately 20% of earth’s surface area.

 It separates Americas in the north, Europe and Africa in west and South America in south by spreading along a large number of islands like Azores, Madeira etc on its eastern side, it is bordered by Africa(west) and south America(south) . 

The Atlantic Ocean has a coastline length of around 100000 km,its average depth is ~ 3700m and its average water temperature varies from 22°C to 24°C.

3. The Indian Ocean

It covers an area of about 14% of Earth’s surface area and has a coastline length of around 60000 km.

 It separates the Indian subcontinent in the south(from which it got its name) and Asia in the north, with Australia and some other islands lying in between them.

 The region is bounded by the equator in north, the Antarctic continent (from which it is separated by the Southern ocean) in south, on east by India and on west by Africa .

This ocean has the second largest average depth (after Pacific ocean) of ~ 3800m.The temperature ranges from 25°C to 28°C.

4. The Southern Ocean

It is a sea of extreme conditions, covering about 10% of earth’s surface area and is the fourth largest ocean in terms of area. 

The southern ocean does not have any land on its border except for the very small Antarctic continent(which is surrounded by this sea).

 It extends around 20°S to 80°S, thus it surrounds Antarctica from all sides.

It also separates Chile from Tierra del Fuego, South Georgia and South Sandwich Islands etc 

.The average depth of this sea is ~ 3700m,the temperature ranges from -1°C to 4 °C(in summer) and with freeze in winter season. i.e. coldest part of earth is around the South pole and Southern ocean of earth

5. The Arctic Ocean

It is the smallest ocean and covers an area of about 10% of Earth’s surface area. This ocean separates the Northern hemisphere from the Southern hemisphere(except in Canada where there is a large gulf) .

On its eastern side, it is bordered by North America(particularly by Canada), Eurasia and the North Atlantic Ocean. On its western side, it is bordered by Eurasia, Greenland and North Pacific Ocean .It also separates Greenland from Iceland.

 The average depth of this ocean is ~ 4100 m and the average water temperature varies from 0°C to 4°C on the North pole and from -20°C to 30°C on the other(southern) side .

6. Mediterranean Sea

It is an important sea for the Mediterranean Region (Southeast Europe and Western Asia). 

This sea has many surrounding islands and is therefore a cultural/geographical region. It has a coastline length of around 80000 km,the average depth of this sea is 3700m,the water temperature varies from 0°C to 15°C, it has a large quantity of water which cools down the earth’s atmosphere.

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