"Decadal shifts" refers to changes or shifts that occur over a period of ten years.
Full definition
The PDO manifests as cool upwelling in the northeast Pacific — the upwelling brings with it cold bottom water and associated nutrients which results in
decadal shifts in biological activity (e.g. Mantua, 1997).
Research shows that
decadal shifts of subsurface Atlantic Water temperatures, along the North Atlantic Current, are associated with a progression of heat anomalies from the Gulf Stream region that coincide with sea surface temperatures extending to cover most of the subpolar and tropical North Atlantic; a signal similar to that of the Atlantic Multidecadal Oscillation.
In a new research paper by Chafik et al., hydrographic observations are employed to show that
decadal shifts of subsurface Atlantic Water temperatures, along the North Atlantic Current, are associated with a progression of heat anomalies from the Gulf Stream region that coincide with sea surface temperatures extending to cover most of the subpolar and tropical North Atlantic — a signal similar to that of the Atlantic Multidecadal Oscillation.
The decadal shift in Hadley Cell width and its relationship with ENSO / external forcings draws interesting parallels to the recent «hiatus» in global warming.