We think of icebergs as a sign of a pristine environment. They are white in colour and made of ice formed over millennia from compacted snow. But all icebergs carry debris. As they move, steered by ocean currents, they leave a trail of material in the water and on the sea f loor. This debris contains nutrients and trace elements that are important for plant growth. In this plume of meltwater and debris spreading from an iceberg, phytoplankton are stimulated to grow and multiply.
The phytoplankton absorb carbon dioxide (CO2) from the atmosphere, in the process of photosynthesis. This carbon is deposited on the sea floor in the bodies and excreta of phytoplankton and the organisms that depend on the plankton for food. Icebergs are therefore a little-considered component of the global carbon cycle, helping move carbon, as carbon dioxide, between the atmosphere and ocean (Figure 1).
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