Shinoda, T., H. H. Hendon, and M. A. Alexander, 2004:
Surface and subsurface dipole variability in the Indian Ocean and its relation with ENSO.
Deep Sea Res., 51, 619-635.
ABSTRACT
An ocean general circulation model, forced with observed winds for the
period 195897, was used to examine surface and subsurface temperature
variability in the Indian Ocean and its relation to ENSO. Empirical
orthogonal function (EOF) analysis of temperature anomalies in the
equatorial longitude-depth plane indicates that the leading mode of
variability has a dipole character, with strongest loadings in the
thermocline and more modest loadings at the surface. The subsurface
dipole is weakly correlated with Nino3.4 SST. However, the subsurface
dipole is well correlated with dipole variability at the surface, which
itself is well correlated with ENSO. These results indicate that
"dipole" variability that is independent of ENSO is more prominent at
depth than in the SST. While the influence of ENSO on subsurface
variability is detectable, the ENSO-induced surface dipole is primarily
controlled by surface heat fluxes. On the other hand, subsurface
variations play an important role for surface dipole events that are
independent of ENSO. This is especially true in the eastern Indian Ocean
where the strong surface cooling in late summer is generated by
up-welling and horizontal heat advection in response to basin-wide
surface easterlies.