Meandering versus mesoscale eddies
Most of the variance in the Eulerian average comes from the meandering of the structurally invariant current. This is shown in two ways. Approach 1
Take the observed positions and
directions of maximum flow for each and every section and replace all
data with data using the analytical form (light line) shown in Figure
2 after projecting them onto the ship's track.
Compare the eddy statistics for the two cases, the original data set (solid line) and the synthetic data set (dashed line). Define a 'residual eddy kinetic energy' (rEKE) by subtracting the analytical representation of the Gulf Stream from the observations (dotted line) in Figure 4 (below). | ||||||
Figure 4. The three curves show the velocity variance in 1) stream coordinates from the observed data, 2) using only the light line double-exponential form in Figure 2, and 3) after first removing the same double exponential function from each transect. The abscissa shows distance in km from New Jersey. | ||||||
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In summary, here as at the Pegasus line, most of the observed variance in the region of the Gulf Stream stems from the meandering of the current itself, about 67% of the total between 0 and 2000 m at the Pegasus line (HR) and 80% along the Oleander line at 52 m depth. |