Demystifying Science: What is the Pacific shadow-zone?

Headline : Demystifying Science: What is the Pacific shadow-zone?

Background

  • From the Carbon-14 dating, it was already known that the most ancient water lies in the deep North Pacific.
  • But until now the struggle was to understand why the very oldest waters huddle around the depth of 2km.
  • But now the researchers have found out that at around 2km below the surface of the Indian and Pacific Oceans, there is a ‘shadow zone’ where no vertical movement of water takes place and ocean water suspends for centuries.

 

Shadow zone

  • It is an area of almost stagnant water sitting between the rising currents caused by the rough topography and geothermal heat sources below 2.5km and the shallower wind driven currents closer to the surface.
  • The oldest water in the North Pacific ocean has remained trapped in this shadow zone for over 1,000 years.
  • The researchers have found the bottom water cannot rise above 2.5km below the surface, leaving the region directly isolated.

 

Possibilities Ahead

  • The research suggests that this stagnant water in the shadow zone is a consequence of the shape of the ocean floor and its impact on vertical circulation.
  • As this isolated shadow zone traps millennia old ocean water, there is a possibility that it might have trapped nutrients and carbon which can have a direct impact on the capacity of the ocean to modify climate over centennial time scales.
Section : Environment & Ecology

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