Abstract:
The origin of the Pacific Decadal Oscillation (PDO),
the leading mode of sea surface temperature variability for
the North Pacific, is a matter of considerable debate. One
paradigm views the PDO as an independent mode centered
in the North Pacific, while another regards it as a largely
reddened response to El Nino-Southern Oscillation (ENSO)
forcing from the tropics. We calculate the Southern
Hemisphere equivalent of the PDO index based on the
leading mode of sea surface temperature variability for the
South Pacific and find that it adequately explains the spatial
structure of the PDO in the North Pacific. A first-order
autoregressive model forced by ENSO is used to reproduce
the observed PDO indices in the North and South Pacific.
These results highlight the strong similarity in Pacific
decadal variability on either side of the equator and suggest
it may best be viewed as a reddened response to ENSO.
