Interdecadal Sea Surface Temperature Variability in the Equatorial Pacific Ocean. Part I: The Role of Off-Equatorial Wind Stresses and Oceanic Rossby Waves

McGregor, Shayne and Holbrook, Neil J. and Power, Scott B. (2007) Interdecadal Sea Surface Temperature Variability in the Equatorial Pacific Ocean. Part I: The Role of Off-Equatorial Wind Stresses and Oceanic Rossby Waves. Journal of Climate, 20 (11). pp. 2643-2658. ISSN 0894-8755


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 (OffEqWVF), 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 Ni \~ n o-4 (Ni \~ n o-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 Ni \~ n o-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 off-equatorial zone and the Ni \~ n o-3 region, with the Ni \~ n o-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.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 05 Jan 2022 22:45
Last Modified: 05 Jan 2022 22:45
Uncontrolled Keywords: Interdecadal Pacific oscillation; Ocean dynamic forcing; Rossby wave; Sea surface temperature
Fields of Research (2008): 04 Earth Sciences > 0401 Atmospheric Sciences > 040105 Climatology (excl.Climate Change Processes)
Fields of Research (2020): 37 EARTH SCIENCES > 3702 Climate change science > 370202 Climatology
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9603 Climate and Climate Change > 960304 Climate Variability (excl. Social Impacts)
Socio-Economic Objectives (2020): 19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1905 Understanding climate change > 190502 Climate variability (excl. social impacts)
18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180506 Oceanic processes (excl. in the Antarctic and Southern Ocean)
Identification Number or DOI: https://doi.org/10.1175/JCLI4145.1
URI: http://eprints.usq.edu.au/id/eprint/44906

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