Steer due East around Antarctica

Lively Data, July 21, 2008

Among one of our Lively Data in 2006, a method was proposed to represent the eddy kinetic energy (EKE) via the Live Access Server. This index, calculated using the expression EKE = 1 / 2 x (U² + V²) is used in the study of mesoscale phenomena to assess the energy carried by the eddies structures. Its expression has not changed, but the way to transcribe it in the new version of LAS is modified (see details below).

The Antarctic Circumpolar Current, encountering neither hindrance nor obstacle, is the strongest current in the world. The EKE, easily represented with the LAS, shows strong eddy kinetic activity at key locations like confluence of the waters (Basin of Argentina, Mozambique plateau, Tasman Sea) and near important topographic thresholds (east of the Drake Strait, west of the Kerguelen plateau, east of the Macquarie rise). The bottom topography therefore influence the eddy activity dissipating surface eddy kinetic energy.

Eddy Kinetic Energy in the Antarctic Circumpolar Current, the January 23, 2008. At the top, an overlooking 360° and down, zoom in on areas with strongest eddy kinetic energy. The maps presented here correspond to a montage of maps less extensive in longitude, in order to obtain an aesthetic and legible representation of the phenomenon.

Select "compare two" using "delayed time absolute geostrophic velocities" dataset: first variable will be U component, second one will be V component. In "output options" write $^2/2 in "evaluate expression" field (to compute (U²/2); to compute V²/2, in the "evaluate expression 2nd variable", write -1*$^2 . You will obtain (-V²/2) variable, so as to plot (U²)-(-V²) in "constraints" menu, which select "difference plot".

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