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Science Meetings

El Niño Low Salinity Equatorial Jets
Clarke, A. and Zhang, X. (22-May-17)

Fundamental to El Niño dynamics is the eastward movement of the western equatorial Pacific warm/fresh pool edge during El Niño and its westward movement during La Niña. Analysis of TAO/TRITON salinity and temperature measurements, as well as Aquarius sea surface salinity (SSS) and satellite altimetry, show that this zonal movement is mostly controlled by a shallow 23cm/s narrow jet. This zonal jet is confined to only a few degrees north and south of the equator in the top 50m-70m of the water column. The jet and its zonal movement result from a coupled ocean/atmosphere instability in which the jets are driven by westerly wind anomalies during El Niño and easterly wind anomalies during La Niña. Preliminary work in the eastern equatorial Pacific suggests that there is also a shallow, narrow, low-salinity interannual zonal flow centered at 1 degree N that stretches for thousands of km and causes the interannual surface flow maximum to shift north of the equator. We are just beginning to examine its dynamics.