Dynamic and Thermodynamic Control of the Response of Winter Climate and Extreme Weather to Projected Arctic Sea-Ice Loss

Abstract

A novel sub-sampling method has been used to isolate the dynamic effects of the response of the North Atlantic Oscillation (NAO) and the Siberian High (SH) from the total response to projected Arctic sea-ice loss under 2°C global warming above preindustrial levels in very large initial-condition ensemble climate simulations. Thermodynamic effects of Arctic warming are more prominent in Europe while dynamic effects are more prominent in Asia/East Asia. This explains less-severe cold extremes in Europe but more-severe cold extremes in Asia/East Asia. For Northern Eurasia, dynamic effects overwhelm the effect of increased moisture from a warming Arctic, leading to an overall decrease in precipitation. We show that the response scales linearly with the dynamic response. However, caution is needed when interpreting inter-model differences in the response because of internal variability, which can largely explain the inter-model spread in the NAO and SH response in the Polar Amplification Model Intercomparison Project.