Diverse Eurasian Winter Temperature Responses to Barents‐Kara Sea Ice Anomalies of Different Magnitudes and Seasonality

The sea‐ice‐driven component of observed Eurasian temperature variability, estimated by comparing multimodel large‐ensemble simulations prescribed with either time‐varying or climatological sea‐ice, suggests an intermittent causal effect of Barents‐Kara sea‐ice on Eurasian winter temperature. To understand this intermittency better, bespoke atmospheric model experiments were conducted with the seasonality, sign, and magnitude of sea‐ice anomalies systematically altered. Stronger Eurasian cooling is found in response to modest than to large autumn sea‐ice loss because of nonlinear wave‐mean‐flow interactions that, via a stratospheric pathway, govern the dynamical responses. Winter sea‐ice loss tends to induce Eurasian warming, via thermodynamical effects, which scale approximately linearly with the magnitude of sea‐ice loss. Complete loss of sea‐ice led to Eurasian warming, suggesting the thermodynamical response dominates when sea‐ice loss is sufficiently large. Our results have implications for the stationarity, or lack thereof, of Arctic‐to‐midlatitude connections, and also for reconciling discrepancies between model experiments with different sea‐ice perturbations.