Are Southern Ocean Swells important for ENSO and Indian Ocean Dipole?

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Tuesday, 6 January 2015: 5:00 PM
224A (Phoenix Convention Center - West and North Buildings)
Yalin Fan, US Naval Research Laboratory, Stennis Space Center, MS; and E. Rogers and T. Jensen

Several field observations have suggested that when long swells propagate into light wind regions, they can interaction with the air above and create wave driven wind, and thus give momentum to the atmosphere and dissipate. Since the equatorial East Pacific and Indian Ocean are dominated by Southern Ocean Swells with light winds, the interaction between the local winds and these long waves could have important effect on SST and mixed layer depth in these regions. The possibility of a teleconnection between the Southern Ocean swells and SST anomalies in the Eastern Pacific Niņo regions and southeastern Indian Ocean is investigated using numerical models. Southern Ocean swells are found to contribute to more than 50% of wave to atmosphere momentum flux (WAMF) in the equatorial Eastern Pacific and Indian Ocean. The corresponding modeled turbulent kinetic energy flux (TKEF) reduction anomaly in the Niņo 3 region is in opposite phase of reported SST anomaly, suggesting the Southern Ocean swells may play an important role in regulating the SST anomalies in this region. The modeled bi-monthly averaged TKEF reduction in the southeastern Indian Ocean can reach 5% during austral winter, and is well correlated with the Indian Ocean Dipole (IOD) mode. TKEF reduction in the central Indian Ocean during May-June 2007 is suspected to play an important role in reducing the unfavorable conditions for positive IOD during La Niņa years.