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Showing posts from January, 2018

Ocean ventilation: oxygen pathways from the ocean's surface to the ocean's interior

As land-dwelling animals, we breathe plentiful oxygen from the atmosphere, except perhaps if we are climbing a high mountain summit where oxygen is more scarce. But ocean-dwelling animals are often not as fortunate as we are when it comes to oxygen abundance.   To begin with, oxygen as a gas is NOT easily dissolved in water. Though a liter of seawater weighs nearly 1000 times more than a liter of air, that very same liter of water contains about 40 times less oxygen than one liter of air (0.008 g versus 0.3g).  But things can get much worse than this, because below the surface layer, oxygen can litterally go down to zero. At 300 m depth, vast expanses of the ocean contain a very small percentage of the amount of  oxygen these same waters contained when they were last found at the sea surface, in direct contact with the atmosphere. This percentage gets very close to zero in the northern Indian Ocean and the eastern equatorial Pacific, and actually reaches zero in th