I’m not sure I quite understand what the Pacific Decadal Oscillation is, but here’s a new paper suggesting it’s sort of nothing at all. Or, more precisely, that it’s really a combination of other things, not a thing in and of itself.

(climate and drought wonks go ahead and click through – the rest of you can move along, nothing really to see here)

The PDO is a statistical construct – the “leading principal component of North Pacific monthly sea surface temperature variability” – that’s been linked to long-term drought on decadal scales in the southwest (and wet decadal-scale periods as well). So, for example, the drought of the 1950s corresponds to a long period of negative PDO. It’s sort of like El Niño and La Niña, but on much longer time scales. The question always has been what might be the physical mechanism that creates such a lingering decadal-scale climate phenomenon. Now Schneider and Cornuelle seem to be arguing that it’s the product of a number of different interacting phenomena at various time scales – ENSO, the Aleutian low, ” zonal advection in the Kuroshio–Oyashio Extension”. Sort of like the beautiful rich undertones from a grand piano:

These results support the hypothesis that the PDO is not a dynamical mode, but arises from the superposition of sea surface temperature fluctuations with different dynamical origins.

What’s not clear to me is what the implications might be for understanding the relationship between what I know as PDO and drought here in New Mexico.