Mid-2000s reversal of North Atlantic warming pattern reshapes hemispheric circulation and Eurasian cold extremes

Abstract Under global warming, North Atlantic sea surface temperatures (SSTs) have warmed highly non-uniformly, yet the role of evolving SST spatial structure in driving large-scale atmospheric reorganizations remains poorly understood. Here, we reveal a pronounced meridional reversal in North Atlantic SST trends around the mid-2000s: accelerated mid-latitude warming replaced earlier subpolar-dominated warming, effectively flipping the basin-wide meridional SST gradient. Focusing on internal climate variability, this oceanic shift was accompanied by a coherent atmospheric cascade, marked by a poleward migration of the North Atlantic mid-latitude westerly jet, a reorganization of Rossby waveguide pathways, and a pronounced shift of the Eurasian teleconnection pattern. Critically, the extreme cold event hotspots exhibited a progressive southward displacement across Eurasia throughout the successive research phases. These changes reflect a multi-stage reorganization of hemispheric circulation modulated by the continuous dynamic evolution of internal atmospheric variability distinct from the global warming signal. Our results suggest that robust climate attribution and future risk assessment must explicitly account for the continuous dynamic evolution of spatial SST patterns and their localized gradients, rather than relying on static basin-mean metrics.