Reversal of the warm Arctic-cold Eurasia intraseasonal coupling by CO2 removal

Abstract

Midlatitude winter climate variability arises partly from its interactionhttps://www.webofscience.com/wos/woscc/full-record/WOS:001777099900001s with Arctic climate variability. A prominent example is the intraseasonal coupling between warm temperature anomalies over the Barents-Kara Seas and cold anomalies over central Eurasia, commonly referred to as the warm Arctic-cold Eurasia (WACE) relationship. Numerous studies have examined how this coupling may weaken under continued greenhouse gas warming. Yet, it remains unclear whether the WACE response to CO2 warming reflects an irreversible change in atmospheric circulation or a reversible response to altered background conditions. In this study, the reversibility of the WACE relationship is investigated using a large-ensemble CO2 ramp-up and ramp-down experiment. The WACE relationship is projected to weaken under increasing CO2 concentrations. This weakening is largely reversed when CO2 concentrations are reduced, while hysteresis appears during the stabilization period. These changes are closely tied to those in local baroclinicity over Eurasia, which are governed primarily by changes in the meridional temperature gradient. This result suggests that the projected weakening of the Arctic-midlatitude coupling reflects a dynamically coherent forced response rather than intrinsic internal variability.