Early Bloom Trigger

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Science  06 Jul 2012:
Vol. 337, Issue 6090, pp. 10
DOI: 10.1126/science.337.6090.10-e
CREDIT: BROR JÖNSSON/NASA

Springtime phytoplankton blooms occur when high nutrient concentrations are combined with abundant sunlight and a stratified upper ocean layer. It has been thought that stratification occurs because in the spring, seasonal warming causes the water to expand, making it less dense, which creates a layer resistant to mixing from below. Now, Mahadevan et al. (p. 54; see the Perspective by Martin) have combined observations of the upper water column from the subpolar North Atlantic with ocean model simulations, which demonstrate that the initial stratification can be triggered by the dynamic effects of passing ocean eddies. These eddies can advance the time of the bloom by 20 to 30 days.

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