Relative dispersion in the subsurface North Atlantic

Pair statistics are calculated for subsurface floats in the North Atlantic. The relative diffusivity (the derivative of the mean square particle separation) is approximately constant at large scales in both eastern and western basins, though the implied scale of the energy-containing eddies is greater in the west. But the behavior at times soon after pair deployment is quite different in the two basins; in the west the diffusivity grows approximately as distance to the 4/3 power, consistent with an inverse turbulent cascade of energy (or possibly of mixing superimposed on a mean shear), but in the east the diffusivity grows more slowly, as for instance in simple stochastic systems. Exponential stretching, expected in an enstrophy cascade, is not resolved in any region; however, this may reflect only that the present pair separations are too large initially.