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

摘要

The sea-ice-driven component of observed Eurasian temperature variability, estimated by comparing multimodel large-ensemble simulations prescribed with either time-varying or climatologi-cal sea-ice, suggests an intermittent causal effect of Barents-Kara sea-ice on Eurasian winter temperature. To understand this in-termittency 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.