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

• Main Authors: Casselman, Jake W., Lübbecke, Joke F., Bayr, Tobias, Huo, Wenjuan, Wahl, Sebastian, Domeisen, Daniela I. V.
• Format: Text
• Language: English
• Published: 2022
• Subjects: Pacific; North Atlantic
• Online Access: https://doi.org/10.5194/wcd-2022-57; https://wcd.copernicus.org/preprints/wcd-2022-57/

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.