Preprints
https://doi.org/10.5194/wcd-2022-57
https://doi.org/10.5194/wcd-2022-57
 
07 Nov 2022
07 Nov 2022
Status: this preprint is currently under review for the journal WCD.

The Teleconnection of Extreme ENSO Events to the Tropical North Atlantic in Coupled Climate Models

Jake W. Casselman1, Joke F. Lübbecke2, Tobias Bayr2, Wenjuan Huo2, Sebastian Wahl2, and Daniela I. V. Domeisen1,3 Jake W. Casselman et al.
  • 1Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • 2GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
  • 3Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland

Abstract. El Niño–Southern Oscillation (ENSO) in the tropical Pacific is known to have remote effects on the sea surface temperatures (SSTs) in the tropical North Atlantic (TNA). Here, the TNA SSTs are positively correlated with ENSO in boreal spring following an ENSO event. The ENSO-TNA teleconnection is also not straightforward as the response of TNA SSTs may be nonlinear to the strength of ENSO (i.e., how strongly the Atlantic reacts to an increase in strength of the Pacific signal), especially during extreme ENSO events. However, the number of extreme ENSO events in observational data remains limited, restricting our ability to investigate the influence of observed extreme ENSO events. To overcome this issue and to further evaluate the nonlinearity of the TNA SSTA response, two coupled climate models are used, namely the Community Earth System Model version 1-– Whole Atmosphere Community Climate Mode (CESM-WACCM) and the Flexible Ocean and Climate Infrastructure version 1 (FOCI). Our results show that the TNA responds linearly to extreme El Niño events in both models but nonlinearly to extreme La Niña events for CESM-WACCM. A large portion of the nonlinearity during La Niña is explained by the interaction between Pacific SSTAs and the overlying troposphere. Overall, our study shows that CESM-WACCM and FOCI are capable of reproducing the ENSO-TNA teleconnection and expands on key differences between climate models and reanalysis.

Jake W. Casselman et al.

Status: open (until 05 Jan 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Jake W. Casselman et al.

Jake W. Casselman et al.

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Short summary
El Niño–Southern Oscillation (ENSO) has remote effects on the tropical North Atlantic (TNA), but the connections’ nonlinearity (strength of response to an increasing ENSO signal) is not always well represented in models. Using the Community Earth System Model version 1-– Whole Atmosphere Community Climate Mode (CESM-WACCM) and the Flexible Ocean and Climate Infrastructure version 1, we find that the TNA responds linearly to extreme El Niño, but nonlinearly to extreme La Niña for CESM-WACCM.