How Does the High‐Latitude Thermal Forcing in One Hemisphere Affect the Other Hemisphere?

Significant progress has been made in our understanding of extratropical impacts on the tropical climate via energetics framework. It is of question whether the impact of extratropical thermal forcing in one hemisphere would extend far into high‐latitudes of the other hemisphere. We examine the possibility of the pole‐to‐pole linkage via atmospheric teleconnections by imposing a cyclic surface thermal forcing in the northern extratropics of an aquaplanet slab ocean model. We reveal a synchronous temperature response between the two poles mediated by zonal‐mean atmospheric dynamics. A warming in one polar region leads to a strengthened Hadley circulation of the unforced hemisphere, fluxing more momentum toward the subtropics, thereby pulling the eddy‐driven jet equatorward. A consequent anomalous descent over the polar region causes warming. The polar surface warming in the unforced hemisphere reaches 30% of that in the forced hemisphere, inferring a significance of the pole‐to‐pole connection. Plain Language Summary Regional climate change effects can be global. This paper reveals a pole‐to‐pole linkage in the absence of ocean dynamics. A high‐latitude surface thermal forcing confined to one hemisphere causes changes in the tropical circulation and mid‐latitude jet, thereby inducing a secondary circulation in the unforced hemisphere. The atmosphere‐driven pole‐to‐pole connection is characterized by synchronous temperature changes between the two poles. We speculate the factors not considered in this study such as ocean‐biogeochemistry feedback may shift temperature changes from being synchronous to asynchronous on longer than multidecadal timescales. Hence, future studies are warranted that gradually add complexities to a model to elaborate pole‐to‐pole teleconnection. Key Points High‐latitude thermal forcing confined to one hemisphere can cause surface temperature changes globally including the opposite pole The pole‐to‐pole linkage via atmospheric pathway results in synchronous polar temperature changes The interhemispheric teleconnection leads to mini‐global warming in response to heating confined to one hemisphere