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Effect of the indonesian tidal mixing on tropical climate system

Par ecola — Dernière modification 04/03/2014 10:15

The sensitivity of the tropical climate to tidal mixing in the Indonesian Archipelago (IA) is investigated using a coupled general circulation model.

 

SST_SSS_anomalies

It is shown that the introduction of tidal mixing considerably improves water masses properties in the IA, generating fresh and cold anomalies in the thermocline and salty and cold anomalies at the surface. The subsurface fresh anomalies are advected in the Indian Ocean thermocline and ultimately surface to freshen the western part of the basin whereas surface salty anomalies are advected in the Leuwin current to salt waters along the Australian coast.

 

schema_couple

 

The ~0.5°C surface cooling in the IA reduces by 20% the overlying deep convection. This improves both the amount and structure of the rainfall and weakens the wind convergence over the IA, relaxes the equatorial Pacific trade winds and strengthens the winds along Java coast. These wind changes causes the thermocline to be deeper in the eastern equatorial Pacific and shallower in the eastern Indian Ocean. The El Nino Southern Oscillation (ENSO) amplitude is therefore slightly reduced while the Indian Ocean Dipole/Zonal Mode (IODZM) variability increases. IODZM precursors, related to ENSO events the preceding winter in this model, are also shown to be more efficient in promoting an IODZM thanks to an enhanced wind/thermocline coupling.

Changes in the coupled system in response tidal mixing are as large as those found when closing the Indonesian Throughflow, emphasizing the key role of IA on the Indo-Pacific climate.

 

precip_sintex

 

More detailed in :

Koch-Larrouy A., M. Lengaigne, S. Masson, G. Madec, P. Terray, (2009a) Indonesian tidal mixing effect on climate system, Climate Dynamic, DOI 10.1007/s00382-009-0642-4.

 

 

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