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- Title
The Impacts of a Weakened Atlantic Meridional Overturning Circulation on ENSO in a Warmer Climate.
- Authors
Liu, Wei; Duarte Cavalcante Pinto, David; Fedorov, Alexey; Zhu, Jiang
- Abstract
This study quantifies the impacts of the Atlantic Meridional Overturning Circulation (AMOC) on the El Niño–Southern Oscillation (ENSO) under anthropogenic warming by comparing climate change model simulations with declining and fixed strengths of the overturning. After the 1980s, a weakened AMOC is shown to reduce the strength of the annual cycle of sea surface temperature (SST) in the eastern equatorial Pacific and induce anomalous cross‐equatorial northerly winds there, which strengthens ENSO variability by about 11%. An analysis of the Bjerknes stability index reveals that this intensification of ENSO results mainly from enhanced Ekman upwelling feedback due to amplified atmospheric wind response to SST anomalies and oceanic upwelling response to equatorial wind stress anomalies. The weakened AMOC also promotes the occurrence of Central Pacific El Niño events and reduces ENSO skewness. These AMOC impacts on ENSO magnitude and complexity throughout the twenty‐first century are however smaller than ENSO variations expected from internal climate variability. Plain Language Summary: Here, we use climate model simulations to study how changes in the Atlantic Meridional Overturning Circulation (AMOC) influence the El Niño–Southern Oscillation (ENSO) in a warming climate. We find that the overturning circulation slowdown caused by global warming can strengthen the ENSO variability by about 11% over 1981–2100 by reducing the annual cycle of sea surface temperature and cross‐equatorial winds in the eastern equatorial Pacific. The detailed physical mechanism explaining this ENSO intensification involves changes in ocean‐atmosphere feedback. We also find that the declining AMOC makes El Niño events with the Central Pacific temperature pattern more frequent. The above effects of the AMOC on ENSO are however smaller than differences expected from model internal climate variability. Key Points: Relative to the simulated future state with reduced El Niño–Southern Oscillation (ENSO) variability, Atlantic Meridional Overturning Circulation (AMOC) slowdown strengthens ENSO by amplifying Ekman upwelling feedbackAMOC slowdown facilitates the occurrence of Central Pacific El Niño eventsAMOC impacts on ENSO are smaller than model internal variability during the twenty‐first century
- Subjects
ATLANTIC meridional overturning circulation; GLOBAL warming; EL Nino; CLIMATE change models; OCEAN temperature; SOUTHERN oscillation
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 8, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL103025