Jan Hafner (IPRC/SOEST, University of Hawaii, USA)

Analysis of historical data of mesoscale sea level anomaly reveals robust global pattern of its annual cycle (Figure). Outside of the tropics, the annual signal is initiated on the eastern boundaries of all oceans and propagates westward consistently with the dynamics of Rossby waves. Locations of 30% of documented mesoscale eddies (both cyclonic and anticyclonic) are consistent with the phase of the annual signal. This suggests that, contrary to the stochastic turbulent concept, formation and propagation of eddies may be anchored to such basin-wide phenomena as Rossby waves, beta-plumes and striations.
Our finding will help to better understand the dynamic of mesoscale eddies and relation of their statistics to large-scale, time-mean or low-frequency ocean phenomena and to improve predictions of seasonal variability of sea level, both globally and locally.

Figure. Month of maximum SLA in daily climatology, high-pass filtered with 5-degrees longitude-latitude filter.