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Impacts of subtropical upper ocean variability on equatorial Indian Ocean

K V Ramesh(1)

(1) C-MMACS, NAL Belur Campus, Bangalore 560037, India


The region between the core of the trade winds and the maximum westerlies which stretches around the globe between approximately 20° and 45° on either side of the Equator, is characterised by negative wind-stress curl in the atmosphere and by associated Ekman transport convergence in the ocean. The seasonal Indian and Asian monsoons affect the entire tropical Indian Ocean and western Pacific regions. Studies have shown that the interannual and interdecadal variability of air-sea interaction in the southern subtropical Indian Ocean are directly connected with the air-sea interactions of the tropical Indian Ocean. In the northern part of the zone the prevailing winds are light and variable, while in the southern area moderate to strong westerly winds prevail. Furthermore, studies of in situ measurements and a model-assimilated dataset reveals a strong influence of subsurface thermocline variability on sea surface temperature (SST) in this upwelling zone. In this study, we examine the sub-tropical upper ocean variability of temperature and salinity from ARGO, XBT and assimilated data sets. POP OGCM high resolution simulations are made to understand the zonal/merdional circulations and their contributions to the equatorial thermal structure. The weekly SSHA (TOPEX/JASON) datasets are used to measure the heat content variability in this above region. The results show that the sub-tropical variability significantly affects the tropical Indian Ocean. Moreover results indicate that the year to year off-equatorial sub-surface temperature variability may be due to remote forcing such as ENSO.



                 Last modified: 07.10.03