The contribution of eddies to striations in absolute dynamic topography

Distinct 4 year averages of absolute dynamic topography reveal striations in all ocean basins during 1993-2008. Striations are alternating mesoscale jet-like structures observed in time-averaged zonal geostrophic velocity, (u) over bar. They are characterized by speeds O(1 cm s(-1)) and are nominally separated by 200 km in the meridional direction. Similar patterns have been observed in sea level anomaly, mean dynamic topography, and Argo float measurements. Use of a tracked-eddy database in concert with a contour identification and eddy removal algorithm demonstrates that eddies are a dominant source of striations in (u) over bar in the South Pacific (20 degrees S-50 degrees S, 200 degrees E-280 degrees E). Eddies with lifetimes >= 4 weeks account for 46-57% of the variance in u and correlation coefficients between total and eddy-only u are 0.90-0.93. Attention is given to the ability of the algorithm to correctly identify eddies and suggests that a more appropriate bound on the variance due to eddies is similar to 30-70%. This permits the existence of latent zonal jets and/or beta-plumes. Additional findings of the study include (1) a large number of eddies having a broad range of amplitudes and scales contribute most to the eddy-induced patterns and (2) the standard deviation of (u) over bar does not decay inversely with averaging period as proposed by a model of random eddies. Citation: Buckingham, C. E., and P. C. Cornillon (2013), The contribution of eddies to striations in absolute dynamic topography, J. Geophys. Res. Oceans, 118, 448-461, doi:10.1029/2012JC008231.