The Impact of Oceanic Feedbacks on Stratosphere‐Troposphere Coupling in an Idealized Model.

Stratospheric temperature perturbations (STPs) caused by for example, variations in stratospheric ozone, are an important driver of changes in tropospheric dynamics, particularly pertinent to the long‐term climatic evolution of the Southern Hemisphere. However, the impact of ocean feedbacks on this interaction has not been fully examined. To study it, positive STPs were applied in three otherwise identical, idealized model configurations –atmosphere‐only (A), atmosphere + slab‐ocean (AS), and fully‐coupled atmosphere‐ocean (AO)–and the resulting atmospheric changes compared. In the AO model, changes in the tropics (extratropics) experienced a poleward‐expansion (shift) and positive (negative) feedback after ∼100–200 years, whilst the AS model showed atmospheric and sea surface temperature changes that did not resemble those seen in the AO model. In the AO model, changes in tropical ocean heat content were responsible for the atmospheric changes, attributable to changes in the Ekman transport. These results indicate that full atmosphere‐ocean coupling should be accounted for when studying the long‐term (100+ years) tropospheric response to STPs in the Southern Hemisphere. Validation with higher‐resolution and more realistic models is necessary. Plain Language Summary: In recent decades, the Southern Hemisphere has seen significant climatic changes in response to stratospheric ozone depletion. It is important to understand what impact oceanic feedbacks might have on this response. To that end, experiments were performed, in which temperature perturbations were applied to the stratospheres of three otherwise identical atmospheric models–with/without oceans present–and their results compared. Ocean feedbacks were found to significantly amplify (weaken) and expand (shift) the atmospheric responses toward the poles in the tropics (extratropics) after about 100–200 years. This was caused by wind‐driven changes in sea surface temperatures in the tropics. These results underscore the importance of accounting for oceanic feedbacks when studying long‐term (100+ years) climatic changes, caused by stratospheric changes, in the Southern Hemisphere. However, further verification of these results with higher‐resolution and more realistic models will be necessary to ensure their applicability, and to better quantify their effects. Key Points: Ocean feedbacks significantly alter the atmospheric response to applied stratospheric temperature perturbations after 100–200+ yearsChanges in the tropical and midlatitude ocean heat content, driven by alterations to the Ekman transport, are responsible [ABSTRACT FROM AUTHOR]