Robust but weak winter atmospheric circulation response to future Arctic sea ice loss

• Published in: Nature Communications
• Main Authors: Smith, D., Eade, R., Andrews, M., Ayres, H., Clark, A., Chripko, S., Deser, C., Dunstone, N., Garcia-Serrano, J., Gastineau, G., Graff, L., Hardiman, S., He, B., Hermanson, L., Jung, T., Knight, J., Levine, X., Magnusdottir, G., Manzini, E., Matei, D., Mori, M., Msadek, R., Ortega, P., Peings, Y., Scaife, A., Screen, J., Seabrook, M., Semmler, T., Sigmond, M., Streffing, J., Sun, L., Walsh, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: Arctic; North Atlantic; North Atlantic oscillation; Sea ice
• Online Access: http://hdl.handle.net/21.11116/0000-000A-07D8-B; http://hdl.handle.net/21.11116/0000-000A-07DB-8

The degree to which Arctic sea ice decline influences the mid-latitude atmospheric circulation is widely debated. Here, the authors use a coordinated multi-model experiment to show that Arctic sea ice loss causes a weakening of the mid-latitude westerly winds, but the effect is overall small. The possibility that Arctic sea ice loss weakens mid-latitude westerlies, promoting more severe cold winters, has sparked more than a decade of scientific debate, with apparent support from observations but inconclusive modelling evidence. Here we show that sixteen models contributing to the Polar Amplification Model Intercomparison Project simulate a weakening of mid-latitude westerlies in response to projected Arctic sea ice loss. We develop an emergent constraint based on eddy feedback, which is 1.2 to 3 times too weak in the models, suggesting that the real-world weakening lies towards the higher end of the model simulations. Still, the modelled response to Arctic sea ice loss is weak: the North Atlantic Oscillation response is similar in magnitude and offsets the projected response to increased greenhouse gases, but would only account for around 10% of variations in individual years. We further find that relationships between Arctic sea ice and atmospheric circulation have weakened recently in observations and are no longer inconsistent with those in models.