ENSO-like decadal variability as the "debris" of interannual ENSO

Decadal ENSO-like SST variability in the tropical Pacific has a spatial structure that strongly resembles interannual ENSO variability. By representing the decadal SST pattern as a linear combination of interannual spatial patterns, it can be shown that the decadal ENSO-like pattern results from temporal averaging over SST anomalies that are known to represent precursors to ENSO (via the seasonal footprinting mechanism), the peak of ENSO, and ENSO "left-overs" (produced via the atmospheric bridge and oceanic wave dynamics along the equatorial wave guide). This suggests ENSO-like decadal variability may be described as an average over the "debris" of interannual ENSO.

Results suggest that intrinsically decadal processes are not needed to explain the spatial structure of ENSO-like variability. This does not imply, however, that decadal mechanisms are unimportant for creating decadal time scales. Indeed, any decadal mechanism that can alter the decadal characteristics of ENSO variability should result in an ENSO-like pattern, if averaged over a long enough time.