Simulation and characterisation of the barrier layer in the Indian ocean
The existence of a barrier layer, between the upper mixed layer and the top of the thermocline, was recently noticed and discussed in the tropical Pacific ocean. Such a layer isolates the upper ocean from the thermocline and emphasizes the response of the ocean to the atmospheric forcing. Its presence modifies the sensitivity of the upper ocean to atmospheric forcing, which may be important to understand coupled interactions.
In order to detect the existence of such a structure in the Indian ocean, a multi-year numerical experiment was performed: the LODYC oceanic model was forced with the ERA15 reanalysis, from 1979 till 1993. This simulation was able to capture the different phases of the annual cycle in the Indian ocean, and also exhibited a relatively strong interannual variability. Barrier layer was detected in different regions of the Indian ocean: in the Arabian Sea, at the end of the summer monsoon, in the eastern equatorial Pacific, during the fall. Existence and variability of the barrier layer are characterized and mechanisms contributing to their formation are analyzed.
