Schneider, N., A. J. Miller, M. A. Alexander and C. Deser, 1999:
Subduction of decadal North Pacific temperature anomalies:
Observations and dynamics
Journal of Physical Oceanography, 29, 1056-1070.
Observations of oceanic temperature in the upper 400 m reveal decadal signals that propagate in the thermocline
along lines of constant potential vorticity from the ventilation region in the central North pacific to approximately 18
degrees N in the western Pacific. The propagation path and speed are well described by the geostrophic mean
circulation and by a model of the ventilated thermocline. The approximate southward speed of the thermal signal of 7
mm s(-1) yields a transit time of approximately eight years. The thermal anomalies appear to be forced by
perturbations of the mixed layer heat budget in the subduction region of the central North Pacific east of the date line,
A warm pulse was generated in the central North Pacific by a series of mild winters from 1973 to 1976 and reached
18 degrees N around 1982. After 1978 a succession of colder winters initiated a sold anomaly in the central North
Pacific that propagated along a similar path and with a similar speed as the warm anomaly, then arrived in the
western tropical Pacific at 18 degrees N around 1991. Tropical Ekman pumping, rather than further propagation of
the midlatitude signal, caused the subsequent spread into the equatorial western Pacific and an increase in amplitude.
Historical data show that anomalous sea surface temperature in the equatorial central Pacific is correlated with
tropical Ekman pumping while the correlation with thermal anomalies in the North Pacific eight years earlier is not
significant. These results indicate no significant coupling in the Pacific of Northern Hemisphere midlatitudes and the
equatorial region via advection of thermal anomalies along the oceanic thermocline.