Observational evidence of alternating zonal jets in the world ocean

Abstract

[1] Multiple zonal jets with the east-west velocity direction alternating with latitude are discovered in satellite altimetry data. The time-varying jets are shown to populate every part of the world ocean and its marginal seas and are best seen in the anomaly of geostrophic vorticity. At midlatitudes the jets have a meridional wavelength of about 300 kms with r.m.s. sea level, velocity and vorticity values of 2.4 cm, 6.9 cm/s and 1.5 10 6 s 1, correspondingly. Realistic data from the high-resolution OGCM run on the Earth Simulator are used to justify high vertical coherence of the jets structure and relevance of the jets to an evolving mesoscale eddy field. Strong coupling between the jets and mesoscale eddies is hypothesized. Citation: Maximenko, N. A., B. Bang, and H. Sasaki (2005), Observational evidence of alternating zonal jets in the world ocean, Geophys. Res. Lett., 32, L12607, doi:10.1029/2005GL022728. eddies and meandering frontal jets. Some trajectories of deep floats also indicate the prevalence of zonal currents, but their ensemble fails to resolve individual jets, if any. [4] At present, data with sufficient horizontal and temporal resolution and coverage are only available from remote sensing and are confined to the sea surface. Attempts to detect zonal jets (ZJs) of the nature discussed above are missing in previous studies. This may be partly because the theory of 2D turbulence is more applicable to the deep ocean layers and/or because the wind-driven circulation overwhelms the upper ocean currents. Here, we describe a method to extract the surface signature of ZJs from maps of satellite altimetry. We also use the OFES output to justify the relevance of the extracted signal to deep ZJs. Both datasets are then used to evaluate properties of the jets. 1.