Quasi-decadal variability in the Atlantic basin involving tropics-midlatitudes and ocean-atmosphere interactions

Observational data are used to emphasise a 5- to 7- yr lag between the main modes of variability in the midlatitudes and in the Tropics. Considering t his finding a mechanism for quasidecadal variability based on Tropics- midl atitudes and ocean- atmosphere interaction is described. It appears that th e signal associated with the SST anomalies in the northern region of the tr opical Atlantic is transferred in midlatitudes through the atmosphere and i t will modify the thermal conditions of the ocean upper layers. In 5- 7 yea rs, thermal conditions will affect the SST anomalies in the northern Tropic s reversing their sign. The results suggest that the Tropics get a negative feedback from midlatitudes so that the Tropics- midlatitudes system is cap able of generating an oscillatory mode.