Global Oceanic Mass Transport by Coherent Eddies

Mesoscale eddies are one of the most prominent processes in the world's ocean. The eddy-induced transport of water mass, heat, and energy has a great impact on the ocean and atmosphere. The study of global mass transport by mesoscale eddies is important. However, most existing studies have used Eulerian eddy detection methods. Compared with Lagrangian methods, Eulerian methods fail to distinguish the coherent transport from the incoherent transport induced by eddies. Using a Lagrangian-averaged vorticity deviation (LAVD)-based coherent eddy detection method, this study identifies global coherent mesoscale eddies in the upper 1000 m of the ocean. Based on the eddy dataset, the eddy-induced coherent mass transport is calculated. Compared with Eulerian estimates, the Lagrangian results shown in this study are one order of magnitude smaller. This means that roughly only about 10% of eddy-induced global water mass transport is coherent. The cumulative eddy-induced coherent transport across each latitude or longitude is only around 1 Sv (1 Sv 10(6) m(3) s(-1)), which is much less than the transport induced by wind-driven gyres and thermohaline circulation.