El Niño-Southern Oscillation (ENSO) Impacts Polar Motion and Climate Modeling

New research suggests that the El Niño-Southern Oscillation (ENSO) exerts a significant influence on polar motion, with analysis of coupled climate model output indicating that ENSO signatures are intensified fluctuations in the Bellingshausen Basin and a large-scale see-saw between Pacific and Indian oceans. These patterns are also present in satellite gravimetry data and primarily excite polar motion along 90E. Inferred oceanic angular momentum (OAM) changes account for 40-50% of the variance in observed polar motion excitation during El Niño/La Niña cycles, upon removal of known geophysical fluid effects.

Key Takeaways:

• ENSO exert strong control on interannual length-of-day variations, but its imprint on polar motion excitation remains to be identified.
• Analysis of coupled climate model output suggests that the main ENSO signatures are intensified fluctuations in the Bellingshausen Basin and a large-scale see-saw between Pacific and Indian oceans.
• The inferred OAM changes account for 40-50% of the variance in observed polar motion excitation during El Niño/La Niña cycles.
• ENSO influences polar motion by changing the spatial distribution of ocean mass, with water moving away from the Indian Ocean and the coast of Australia to spread across the Pacific Ocean.
• The research has been peer-reviewed and demonstrates that the characteristic changes in ocean mass and polar motion are also partly seen in global ocean and Earth observations.
• The study suggests that polar motion data may only provide limited insights into variability of this climate mode due to the co-occurrence of ENSO and other oceanic excitation signals.
• The research was supported by the German Research Foundation (DFG) and Projekt DEAL.
• The additional authors for this research include K. M. Lentge, M. Schindelegger, and H. Dobslaw.

Statistics:

• 40-50% of the variance in observed polar motion excitation during El Niño/La Niña cycles is accounted for by inferred OAM changes.
• The analysis of coupled climate model output suggests that the main ENSO signatures are intensified fluctuations in the Bellingshausen Basin and a large-scale see-saw between Pacific and Indian oceans.
• The inferred OAM changes are primarily excitable along 90E in the satellite gravimetry data.

Sources:

• Enso Modulates the Oceanic Excitation of Polar Motion. Geophysical Research Letters, 2025;52(18).
• American Geophysical Union (AGU) - www.agu.org
• German Research Foundation (DFG) - www.dfg.de
• Projekt DEAL - www.projekt-deal.de