Tidal mixing in the Indonesian Seas and its effect on the tropical climate system |
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| Authors: | Ariane Koch-Larrouy Matthieu Lengaigne Pascal Terray Gurvan Madec Sebastien Masson |
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| Institution: | 1. Laboratoire d’Océanographie et du Climat: Expérimentation et Approches Numériques (CNRS/IRD/UPMC/MNHN), case 100, Université Pierre et Marie Curie, boite 100, 4 place Jussieu, 75252, Paris Cedex 05, France
2. National Oceanographic, Centre, Southampton, UK
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| Abstract: | The sensitivity of the tropical climate to tidal mixing in the Indonesian Archipelago (IA) is investigated using a coupled
general circulation model. 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. 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. |
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