Subpolar North Atlantic Ocean Heat Content as a Precursor to 21st-century Arctic Temperature Variability

Arctic surface temperatures exhibit a pronounced multi-decadal oscillation superimposed on the long-term anthropogenic warming trend, yet its drivers remain poorly understood. Here, we investigate the mechanisms governing this 21st-century variability using the Community Earth System Model Large Ensemble combined with a time-evolving radiative kernel method. We identify a key oceanic mechanism initiated in the subpolar North Atlantic, where variability in upper-layer (0–200 m) ocean heat content precedes fluctuations in poleward ocean heat transport (OHT) by approximately five years. These OHT anomalies, in turn, trigger Arctic surface temperature changes by two years. OHT directly accounts for 44.5% of Arctic temperature variability, while local feedbacks (principally albedo and lapse rate) amplify this signal, contributing an additional 53.5%. This process of oceanic preconditioning and subsequent amplification is most pronounced in the Barents, Kara, and East Siberian Seas. These findings underscore that oceanic processes, originating in the subpolar North Atlantic and propagating into the Arctic, are critical in modulating the phase of Arctic multi-decadal temperature variability. Understanding this sequential mechanism could enhance decadal to multi-decadal climate predictions and future projections.