Changes in the spatial structure of strong and moderate ElNino events under global warming

Abstract

In this study, we examine how the spatial structures of strong and moderate ElNino events have changed due to global warming using the Coupled Model Intercomparison Project Phase 5 (CMIP5) coupled general circulation models (CGCMs) based on a historical run and a Representative Concentration Pathways (RCP)4.5 run. The centre of the maximum anomalous sea surface temperature (SST) in the moderate ElNino has shifted significantly westward from the historical run to the RCP4.5 run; however, this is not seen with the strong ElNino events. Further analysis indicates that the centre of the maximum anomalous SST in the moderate ElNino with a negative Pacific Decadal Oscillation (PDO) phase shifted westward around the international dateline from the historical run to the RCP4.5 run. This is in contrast to the moderate ElNino, which shows a positive PDO phase. We also briefly discuss a possible mechanism on the change in the spatial structure of moderate ElNino with a negative phase of PDO from the historical run to the RCP4.5 run.