EGU21-2881, updated on 17 Feb 2022
EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

ENSO response to changes in the tropical Indian ocean temperature

Brady Ferster1, Alexey Fedorov1,2, Juliette Mignot1, and Eric Guilyardi1,3
Brady Ferster et al.
  • 1LOCEAN-IPSL (Sorbonne Université, CNRS, IRD, MNHN), Paris, France. (
  • 2Department of Earth and Planetary Sciences, Yale University, New Haven, CT, USA.
  • 3NCAS-Climate, University of Reading, Reading, UK.

Since the start of the 21st century, El Niño-Southern Oscillation (ENSO) variability has changed, supporting generally weaker Central Pacific El Niño events. Recent studies suggest that stronger trade winds in the equatorial Pacific could be a key driving force contributing to this shift. One possible mechanism to drive such changes in the mean tropical Pacific climate state is the enhanced warming trends in the tropical Indian Ocean (TIO) relative to the rest of the tropics. TIO warming can affect the Walker circulation in both the Pacific and Atlantic basins by inducing quasi-stationary Kelvin and Rossby wave patterns. Using the latest coupled-model from Insitut Pierre Simon Laplace (IPSL-CM6), ensemble experiments are conducted to investigate the effect of TIO sea surface temperature (SST) on ENSO variability. Applying a weak SST nudging over the TIO region, in four ensemble experiments we change mean Indian ocean SST by -1.4°C, -0.7°C, +0.7°C, and +1.4°C and find that TIO warming changes the magnitude of the mean equatorial Pacific zonal wind stress proportionally to the imposed forcing, with stronger trades winds corresponding to a warmer TIO. Surprisingly, ENSO variability increases in both TIO cooling and warming experiments, relative to the control. While a stronger ENSO for weaker trade winds, associated with TIO cooling, is expected from previous studies, we argue that the ENSO strengthening for stronger trade winds, associated with TIO cooling, is related to the induced changes in ocean stratification. We illustrate this effect by computing different contributions to the Bjerknes stability index. Thus, our results suggest that the tropical Indian ocean temperatures are an important regulator of TIO mean state and ENSO dynamics.

How to cite: Ferster, B., Fedorov, A., Mignot, J., and Guilyardi, E.: ENSO response to changes in the tropical Indian ocean temperature, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2881,, 2021.


Display file