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<p>The Southern Indian Ocean Dipole (SIOD) is another mode in the tropical Indian Ocean besides the Indian Ocean Basin mode (IOBM) and the Indian Ocean dipole (IOD). The relationships between El Niño-Southern Oscillation (ENSO) and IOBM/IOD have been widely studied; however, the influence of the ENSO on the SIOD remains unclear. Using observational datasets and the Community Earth System Model (CESM) simulation outputs, we reveal that the relationship between the ENSO and late-winter SIOD displays a significant decadal variation that is modulated by the Atlantic Multidecadal Oscillation (AMO), with strong negative ENSO–SIOD relationship during the positive phase of the AMO. The warm sea-surface temperature anomalies (SSTAs) associated with the AMO drive a range of Indo-Pacific mean climate variation, including more frequent occurrences of the central Pacific (CP)-type ENSO and westward shift of ENSO-related vertical circulation. These mean state changes generate strong northwesterly wind anomalies over the southeastern Indian Ocean, which weaken the climatological southeasterlies and reduce surface evaporation, leading to regional warming. Concurrently, pronounced southerly wind anomalies over the southwestern Indian Ocean enhance the advection of cold polar waters, resulting in regional cooling. These dipole anomalies collectively alter the SIOD, which in turn modulates the ENSO–SIOD relationship. The observed AMO’s influence on this relationship is confirmed by the CESM1 Atlantic pacemaker simulations and CMIP6 model outputs.</p>

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Modulation of Atlantic multidecadal oscillation on the relationship between ENSO and late-winter Southern Indian Ocean Dipole

  • 期刊论文

  • 发表日期：

    2026年5月28日

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  • Meng Xu,
  • Haiming Xu,
  • Jing Ma,
  • Jiechun Deng,
  • Yu Yuan,
  • Heming Bai

摘要

The Southern Indian Ocean Dipole (SIOD) is another mode in the tropical Indian Ocean besides the Indian Ocean Basin mode (IOBM) and the Indian Ocean dipole (IOD). The relationships between El Niño-Southern Oscillation (ENSO) and IOBM/IOD have been widely studied; however, the influence of the ENSO on the SIOD remains unclear. Using observational datasets and the Community Earth System Model (CESM) simulation outputs, we reveal that the relationship between the ENSO and late-winter SIOD displays a significant decadal variation that is modulated by the Atlantic Multidecadal Oscillation (AMO), with strong negative ENSO–SIOD relationship during the positive phase of the AMO. The warm sea-surface temperature anomalies (SSTAs) associated with the AMO drive a range of Indo-Pacific mean climate variation, including more frequent occurrences of the central Pacific (CP)-type ENSO and westward shift of ENSO-related vertical circulation. These mean state changes generate strong northwesterly wind anomalies over the southeastern Indian Ocean, which weaken the climatological southeasterlies and reduce surface evaporation, leading to regional warming. Concurrently, pronounced southerly wind anomalies over the southwestern Indian Ocean enhance the advection of cold polar waters, resulting in regional cooling. These dipole anomalies collectively alter the SIOD, which in turn modulates the ENSO–SIOD relationship. The observed AMO’s influence on this relationship is confirmed by the CESM1 Atlantic pacemaker simulations and CMIP6 model outputs.