Hao Wang: Impacts of Relative Atlantic SST Changes on Atlantic–Pacific Transbasin Interactions
The tropical Atlantic Ocean (TAO) plays an important role in influencing the tropical Pacific climate through atmospheric teleconnections. However, there is a large spread in the simulated TAO mean SSTs relative to the tropical mean across climate models, as well as across prescribed-SST experiments. Given that the tropical mean SST controls the background convection threshold, such variations in relative TAO SST mean states potentially affect the local convection responses to the TAO SST anomalies. Atlantic transbasin interactions may be therefore affected. To identify the impact of relative TAO SST changes on the Atlantic–Pacific connections, we conduct three pairs of AGCM experiments using the ACCESS-CM2 model. These experiments show the atmospheric responses to an anomalous TAO warming under observed, colder, and warmer relative TAO mean states. Experimental results demonstrate that changes in the relative TAO SST significantly modulate the local convective response to underlying TAO SST anomalies. Colder TAO background suppresses the deep convection, generating a weaker Atlantic precipitation response. However, the remote tropical Pacific atmospheric responses are enhanced due to the westward shift of precipitation across the Atlantic and tropical Americas. Opposite changes in Pacific responses are observed when TAO background is warmer despite the weaker magnitudes. This study highlights the importance of relative SST biases in modulating simulated Atlantic–Pacific transbasin interactions, which provides an additional explanation for the misrepresentation of these interactions in coupled models.
Key words: Tropical Atlantic; tropical Pacific; transbasin interactions; relative SST; model biases.