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Abstract

The Australian Bureau of Meteorology Research Centre CGCM and a linear first baroclinic-mode ocean shallow-water model (SWM) are used to investigate ocean dynamic forcing mechanisms of the equatorial Pacific Ocean interdecadal sea surface temperature (SST) variability. An EOF analysis of the 13-yr low-pass Butterworth-filtered SST anomalies from a century-time-scale CGCM simulation reveals an SST anomaly
spatial pattern and time variability consistent with the interdecadal Pacific oscillation. Results from an SWM
simulation forced with wind stresses from the CGCM simulation are shown to compare well with the CGCM, and as such the SWM is then used to investigate the roles of “uncoupled” equatorial wind stress forcing, off-equatorial wind stress forcing (OffEqWF), and Rossby wave reflection at the western Pacific Ocean boundary, on the decadal equatorial thermocline depth anomalies. Equatorial Pacific wind stresses are shown to explain a large proportion of the overall variance in the equatorial thermocline depth anomalies. However, OffEqWF beyond 12.5° latitude produces an interdecadal signature in the Niño-4 (Niño-3) region that explains approximately 10% (1.5%) of the filtered control
simulation variance. Rossby wave reflection at the western Pacific boundary is shown to underpin the OffEqWF contribution to these equatorial anomalies. The implications of this result for the predictability of the decadal variations of thermocline depth are investigated with results showing that OffEqWF generates an equatorial response in the Niño-3 region up to 3 yr after the wind stress forcing is switched off. Further, a statistically significant correlation is found between thermocline depth anomalies in the offequatorial zone and the Niño-3 region, with the Niño-3 region lagging by approximately 2 yr. The authors conclude that there is potential predictability of the OffEqWF equatorial thermocline depth anomalies with
lead times of up to 3 yr when taking into account the amplitudes and locations of off-equatorial region
Rossby waves.

Item Type:	Article
Authors/Creators:	McGregor, S and Holbrook, NJ and Power, S
Journal or Publication Title:	Journal of Climate
ISSN:	0894-8755
DOI / ID Number:	https://doi.org/10.1175/JCLI4145.1
Additional Information:	© 2008 American Meteorological Society
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