Oceanic mass transport by mesoscale eddies

Science  18 Jul 2014:
Vol. 345, Issue 6194, pp. 322-324
DOI: 10.1126/science.1252418

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Spinning up ocean circulation discretely

Ocean eddies with diameters of tens to hundreds of kilometers are an important component of water transport on a global scale. Averaged over periods of many years, ocean circulation is regular and coherent enough to have been described as a conveyor belt. However, over shorter time scales, irregular, discrete events cause significant amounts of water movement—termed mesoscale eddies. Zhang et al. combined data from thousands of autonomous observational devices called ARGO floats with satellite data. The mesoscale eddies moved around as much ocean water as wind or deepwater currents.

Science, this issue p. 322


Oceanic transports of heat, salt, fresh water, dissolved CO2, and other tracers regulate global climate change and the distribution of natural marine resources. The time-mean ocean circulation transports fluid as a conveyor belt, but fluid parcels can also be trapped and transported discretely by migrating mesoscale eddies. By combining available satellite altimetry and Argo profiling float data, we showed that the eddy-induced zonal mass transport can reach a total meridionally integrated value of up to 30 to 40 sverdrups (Sv) (1 Sv = 106 cubic meters per second), and it occurs mainly in subtropical regions, where the background flows are weak. This transport is comparable in magnitude to that of the large-scale wind- and thermohaline-driven circulation.

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