internal tides in the Solomon Sea in contrasted ENSO conditions

Michel Lionel Tchilibou1, Lionel Gourdeau2, Florent Lyard3, Rosemary Morrow4, Ariane Koch-Larrouy3, Damien Allain3 and Bugshin Djath5, (1)United States, (2)LEGOS/IRD, Toulouse, France, (3)LEGOS, Toulouse, France, (4)CNES French National Center for Space Studies, Toulouse Cedex 09, France, (5)LGGE Laboratoire de Glaciologie et Géophysique de l’Environnement, Saint Martin d'Hères, France
The Solomon Sea is the last passageway for the low-latitude western boundary currents of the Southwest Pacific that connect the subtropics to the equator. In this marginal sea strongly influenced by ENSO, the cumulated effects of mesoscale activity and internal tides constraints result in water mass transformation as observed by in situobservations. Based on two regional simulations with and without tides, we document the M2 internal tides characteristics and impacts on water masses during two contrasted ENSO conditions: the 1997-1998 El Niño and the 1999 La Niña. The
generation, propagation and dissipation of the internal tides are sensitive to changes in stratification and mesoscale activity between El Niño and La Niña. The El Niño
conditions, with stratification closer to the surface, are favorable for the propagation of mode 2 M2 baroclinic tide. The la Niña case with a high level of mesoscale activity favors the
appearance of incoherent internal tides. Diapycnal mixing induced by the internal tides is efficient in eroding the salinity maximum of the upper thermocline water, and in
cooling the surface temperature interacting with the atmosphere. The interaction of internal tides with the surface mesoscale activity reduces surface cooling during El
Niño 1998, but increases surface warming during La Niña 1999, with possible impacts on regional air sea interaction.