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The Ocean Conveyor: The flow of water through the deep
sea has been determined primarily with chemical tracers. For example,
dissolved silicate concentrations increase with time as diatoms (phytoplankton
with silica shells) fall into the deep sea and dissolve. Older waters have
more silicate, therefore. The movie loop shows the location of waters at
3000 m depth with progressively higher Si concentrations. The lowest
values are found in the North Atlantic, where cold, low Si waters sink into the
deep sea. These are the youngest deep waters. Increasing Si
concentrations are found through the South Atlantic, around Antarctica and up
into the Indian and South Pacific Oceans. Waters with the highest Si are
found in the North Pacific. These are the oldest deep waters in the
ocean. Deep water forms primarily in the North Atlantic because surface
salinities are greatest in the Atlantic and the saltier water becomes more
dense than Pacific surface water when cooled in the winter.
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