| Summary: | Despite substantial global mean warming, surface cooling has occurred in both the tropical eastern Pacific and Southern Ocean over the past 40 years, influencing both regional climates and estimates of Earth’s climate sensitivity to rising greenhouse gases. Using a paleo-reconstruction dataset of the past 2000 years, we find that sea-surface temperatures (SSTs) over the tropical eastern Pacific and part of the Southern Ocean near the southeast Pacific closely co-vary with each other on decadal to multidecadal timescales. While a tropical influence on the extratropics has been extensively studied in the literature, here we demonstrate that the teleconnection works in the other direction as well, suggesting that the observed tropical eastern Pacific cooling may be connected to the observed Southern Ocean cooling. Using a slab-ocean model, we find that the tropical Pacific SST response to an imposed Southern Ocean surface heat flux forcing is sensitive to the longitudinal location of that forcing, suggesting an atmospheric pathway associated with regional dynamics rather than reflecting a zonal-mean energetic constraint. The transient response shows that an imposed Southern Ocean cooling first propagates into the tropics by mean-wind advection. Once tropical Pacific SSTs are perturbed, they then drive remote changes to the sea-level pressure and surface winds in the extratropics which further enhance both Southern Ocean and tropical cooling. These results suggest a mutually interactive teleconnection between the Southern Ocean and tropical Pacific through atmospheric circulations, and highlight potential impacts on the tropics from the extratropical climate changes over the instrumental record and in the future.
|
|---|