Australia: The Land Where Time Began

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Variability of the Barrier Layer in the Tropical Indian Ocean and Relationship with Indian Ocean Dipole as determined from Argo profiles

In this paper the authors1 examined the interannual variability of the barrier layer (BL) in the southeastern tropical Indian Ocean (SETIO) by the use of temperature and salinity profiles obtained from Argo floats since 2004. It is indicated by their results that off Sumatra there is quasi-permanent barrier layer with a semi-annual cycle and a maximum in November, and that the interannual variability is closely related to the Indian Ocean Dipole (IOD), the IOD leading the BL by 1 month. Upwelling of equatorial Kelvin waves, that are easterly-induced, raise the isothermal layer (IL) off Sumatra during the positive (pIOD) season of 2006.  A mixed layer (ML), that is salinity-stratified, shoals as a result of reduced eastward salty water transport by a weaker Wyrtki jet, despite an offset by a reduced freshwater flux. Thinning of the barrier layer is dominated by thinning of the isothermal layer. Similar processes operate in the opposite direction during the 2010 negative Indian Ocean Dipole (nIOD). The thermocline-mixed layer coupling is enhanced by thinning of the barrier layer during the positive Indian Ocean Dipole, the results of this study indicating that Indian Ocean Dipole positive feedbacks are in turn enhanced by and IOD-induced co-varying barrier layer.

Sources & Further reading

  1. Qiu, Yun, Wenju Cai, Li Li, and Xiaogang Guo. "Argo Profiles Variability of Barrier Layer in the Tropical Indian Ocean and Its Relationship with the Indian Ocean Dipole." Geophysical Research Letters 39, no. 8 (2012): n/a-n/a.
Author: M. H. Monroe
Last updated  29/12/2013
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