Langmuir circulation

Langmuir circulation is a wind driven helix circulation in the ocean with the axis almost parallel to the wind. Irving Langmuir discovered this phenomenon after noticing windrows of seaweed in the Sargasso Sea in 1938 [The open university, "Ocean circulation" Butterworth Heinemann second edition 2001] .

The circulation was found to be 15° to the right of the wind in the northern hemisphere [Stewart, Robert H., "Introduction To Physical Oceanography", Copyright 2002 Fall 2002 Edition] and the helix forming bands of divergence and convergence at the surface. At the convergence zones floating seaweed, foam and debris will concentrate and form the bands Langmuir noticed in 1938. At the surface the circulation will set a current from the divergence zone to the convergence zone and the spacing between these zones are of the order 15-300 m. Below convergence zones narrow jets of downward flow form and the magnitude of the current will be comparable to the horizontal flow. The downward propagation will typically be in the order of meters or tenths of meters and will not penetrate the pycnocline. The upwelling will generally be less intense and take place over a wider band under the divergence zone.

In an observation done at windspeeds of 14 m s^-1 the horizontal spacing of the cells were 20 m and maximum vertical velocity was -18 cm s^-1.

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