Surface warming since 1950 in the off-equatorial south
Indian Ocean (IO) occurs without a consistent surface heat
flux trend, and is accompanied by a shoaling thermocline.
The associated dynamics have not been fully explored.
Using 20th century climate model experiments, we test if
the shoaling thermocline is attributable to a transmission
from the Pacific, where a similar shoaling occurs, and
whether it is climate change-induced. A 22-model average
produces no such signal. An average of a subset of models
that better simulate El Nin˜o-Southern Oscillation (ENSO)
and its transmission produces the right direction of the IO
thermocline trends. The shoaling in this subset average,
taken as anthropogenically induced, is far weaker than the
observed, suggesting a significant multidecadal variability
component in the observed changes. The Pacific
contribution increases with a stronger model ENSO
amplitude and broader meridional structure, highlighting
the importance of realistic ENSO simulations in modelling
long-term change in the IO.

Full Article: http://www.agu.org/pubs/crossref/2008/2008GL034174.shtml

Last Updated: 2008-08-21