Effect of recent Atlantic warming in strengthening Atlantic-Pacific teleconnection on interannual timescale via enhanced connection with the pacific meridional mode

Abstract

The Atlantic warm pool (AWP), which features the highest sea surface temperature (SST) in the western Hemisphere in boreal summer to early fall, has been known to have a significant influence on the climate in its surrounding regions. It is reported that the AWP has become warmer and warmer, so that AWP-SST during a couple of recent decades has been higher than any other period since the twentieth century. Under the increased mean AWP-SST, atmospheric responses to the anomalous AWP-SST are intensified, which corresponds to a higher possibility of deep convection formation. Through Rossby wave propagation induced by the deep convection, AWP signals are able to reach further west toward the central North Pacific. At this moment, anomalous northerly winds are introduced over the North Pacific, which advects negative moist static energy (MSE) into the subtropics and simultaneously contributes to a SST cooling by interacting with northerly mean trade winds. Owing to the Gill-type response to a negative heating anomaly associated with the anomalous SST cooling and the negative MSE, the anomalous northerly winds are further developed over the North Pacific. Such air-sea coupling persists throughout fall to winter, leading to Pacific meridional mode development in the following spring. Subsequently, the PMM acts to boost El Nino and Southern Oscillation events. Coupled model experiments were carried out to investigate the extent to which the mean AWP-SST warming strengthens the Atlantic-Pacific interbasin teleconnection on interannual timescales, and it is proven to support observational analysis.