Oceanography: Division of Oceans (Part-1)

In the previous post, we have dealt with the basic terminology related to the Oceanography. In this post, we will divide Oceans on the following basis like,

  • Penetration of Sun Rays,
  • Bioproductivity,
  • Ecological Division and
  • Morphological Division

So, let’s start our discussion. For the deep study of Oceanography, one needs to classify the Ocean on the basis of their location, productivity and marine life. So, here first we will study regionalisation of Oceans on the basis of Penetration of Sun Rays.

Regionalisation of Oceans

Penetration of Sun Rays

On the basis of penetration of Sun Rays, there are three parts of oceans,

  • Photic Zone
  • Diasphotic Zone
  • Aphotic Zone
Photic, Diasphotic and Aphotic regions of Oceans
Photic, Diasphotic and Aphotic region of Oceans

Photic Zone

So, Photic zone is demarcated by the region up to where Sun rays can penetrate the Ocean. It is generally 260 feet deep from the sea level of the ocean.

As Sun rays are active in this zone, photosynthesis can take place in this region. Because of this, the region has 98% of marine life. Only 1% of marine life can thrive below this zone.

Diasphotic Zone

This is a twilight zone of Ocean. The zone appears deep blue to black in colour. As there is no enough Sunlight, Photosynthesis can not take place in this region.

Aphotic Zone

This is a dark zone of the Ocean. The sunlight never reaches here, so photosynthesis is impossible. The only means to thrive lives in this region is by Chemosynthesis Process. In this microbes lead the food chain. Only 1% of marine life in this zone.

Classification on the basis of Bioproductivity

Bioproductivity of the Oceans
Bioproductivity of the Oceans

Equatorial Zone

This zone has the highest productivity and the highest biodiversity. This is because this region receives the highest solar energy. So, the higher the energy greater will be entropy which will lead to the highest bio productivity. This zone lies between 10°N to 10°S, as shown in the above figure.

Cold Upwelling Zone

This zone lies along the western coast of the continents between 15°-30° Latitudes. It is because here the trade winds become offshore and drive coast water away resulting in cold upwelling zone.

Due to cold upwelling nutrient supply is greater in this region and it attracts swarms of fishes. Coldwater also helps with the multiplication of phytoplanktons.

Polar Fringes/ Arctic and Antarctica Zone

In polar regions, productivity is good. It is because of the mixing of freshwater and saline water. This mixed water creates possibilities for lives to thrive. Example- we will find Whale, Amphibians like Walrus, Penguin and seals here.

Warm and Cold Ocean Current Mixing Zone

When the warm and cold ocean current meets, advection (Horizontal) fog produces. This fog intercepts Ultra-Violet and Infrared rays of Sun. So, obviously, it provides the best conditions for marine life to thrive.

Most of the Fishing banks are at the confluence of warm and cold water current. Example, Grand Bank, Newfoundland, where Labrador cold ocean current meets Gulf Stream warm ocean current.

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