Decadal-scale drivers of South Pacific hydroclimate variability

Skinner, Daniel T., Robbins, Connor ORCID: https://orcid.org/0000-0002-3762-4744, Inglis, Gordon N., Joshi, Manoj ORCID: https://orcid.org/0000-0002-2948-2811, Langdon, Peter, Matthews, Adrian J. ORCID: https://orcid.org/0000-0003-0492-1168, Peaple, Mark, Osborn, Timothy J. ORCID: https://orcid.org/0000-0001-8425-6799 and Sear, David A. (2026) Decadal-scale drivers of South Pacific hydroclimate variability. Quarterly Journal of the Royal Meteorological Society. ISSN 0035-9009

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Abstract

The South Pacific Convergence Zone (SPCZ) is the dominant perennial rainfall feature of the Southern Hemisphere, yet the physical mechanisms driving its variability on decadal to multidecadal time scales are poorly understood. Using prescribed sea-surface temperature (SST) perturbations in the atmosphere-only IGCM4 model, we investigate the direct atmospheric mechanisms by which three major modes of low-frequency climate variability – the Interdecadal Pacific Oscillation (IPO), Atlantic Multidecadal Variability (AMV), and Southern Ocean SST-driven mid-latitude jet shifts – modulate South Pacific hydroclimate. IPO forcing produces the most substantial and spatially coherent SPCZ response: a positive IPO anomaly drives a north-eastward shift in the SPCZ, while a negative IPO shifts the SPCZ southwestward. This behaviour arises from coupled dynamic and thermodynamic changes, with anomalous moisture convergence – rather than altered Rossby wave refraction – emerging as the dominant control on SPCZ position. By contrast, AMV-forced atmospheric teleconnections exert only weak and statistically insignificant impacts on South Pacific precipitation; any apparent signal is best interpreted as an alias of IPO-like SST anomalies in the Pacific. Southern Ocean SST anomalies induce significant shifts in the Southern Hemisphere mid-latitude jet and associated Hadley–Ferrel cell structure, but these changes do not generate a coherent SPCZ displacement. Instead, precipitation changes reflect large-scale regions of anomalous ascent and descent, driven by Hadley and Ferrel cell shifts, rather than modifications to SPCZ dynamics.

Item Type:	Article
Additional Information:	Data Availability Statement: CMIP6 data used to generate IPO and AMV SST anomalies are available from the Earth System Grid Federation, and were accessed via the CEDA archive(Boucher et al., 2018; NASA Goddard Institute for Space Studies (NASA/GISS), 2018; Tatebe & Watanabe, 2018; Danabasoglu et al., 2019; Li, 2019; Swart et al., 2019b; Tang et al., 2019; Wieners et al., 2019; Ziehn et al., 2019). 20th Century reanalysis data are available from the NOAA Physical Sciences Laboratory (Compo et al., 2011).
Uncontrolled Keywords:	amv,ipo,midlatitude jet,spcz,sdg 13 - climate action,das in place,giss), 2018; tatebe & watanabe, 2018; danabasoglu et al., 2019; li, 2019; swart et al., 2019b; tang et al., 2019; wieners et al., 2019; ziehn et al., 2019). 20th century reanalysis data are available from the noaa physical sciences laboratory (compo et al., 2011).,2026 ,/dk/atira/pure/sustainabledevelopmentgoals/climate_action
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA Faculty of Science > Tyndall Centre for Climate Change Research University of East Anglia Research Groups/Centres > Faculty of Science > Research Centres > Tyndall Centre for Climate Change Research
UEA Research Groups:	Faculty of Science > Research Groups > Climatic Research Unit Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Social Sciences > Research Centres > Water Security Research Centre
Depositing User:	LivePure Connector
Date Deposited:	15 Oct 2026 14:16
Last Modified:	18 Oct 2026 05:28
URI:	https://ueaeprints.uea.ac.uk/id/eprint/104799
DOI:	10.1002/qj.70312

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