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

Doug Smith ,Nick Dunstone ,Svenya Chripko ,Leon Hermanson ,Rym Msadek ,Yannick Peings ,Adam A Scaife ,Michael Sigmond ,James A Screen ,Thomas Jung ,Guðrún Magnúsdóttir ,Guillaume Gastineau ,Tido Semmler ,Javier Garcı́a-Serrano ,Rosie Eade ,Daniela Matei ,Adam J Clark ,Melissa Seabrook ,Lantao Sun ,Jan Streffing ,Pablo Ortega ,Jeff Knight ,Elisa Manzini ,Steven C Hardiman ,Xavier J Levine ,Clara Deser ,Lise Seland Graff ,Masato Mori ,Bian He ,Martin B Andrews ,Holly Ayres ,Amber Walsh

doi:10.1038/s41467-022-28283-y

Abstract

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.

Highlights

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
We focus on the boreal winter season (December, January and February, DJF) for which the imposed sea ice changes show reductions around the edges of the ice pack, especially in the Barents-Kara Seas, Sea of Okhotsk, Bering-Chukchi Seas, and Hudson Bay and Labrador Sea (Fig. 1a)
Warm sea surface temperatures (SSTs) are imposed where sea ice is lost in future, producing local maxima of near surface warming response in these regions along with further warming spread throughout the Arctic and into lower latitudes (Fig. 1b)

Summary

Introduction

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. 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. Since the 1990s the Arctic has been warming more than twice as fast as the global average[1], accompanied by rapid loss of sea ice[2] This is consistent with polar amplification of climate change and is expected to continue in response to anthropogenic emissions of greenhouse gases[3]. We elucidate the main physical processes and show that the model spread depends on eddy feedback This is 1.2 to 3 times too weak in the models, suggesting that the real-world weakening of westerly winds lies towards the higher end of the model simulations. The modelled response to Arctic sea ice loss is weak relative to inter-annual variability, though it is similar in magnitude and offsets the projected response to increased greenhouse gases

Methods

Results

Conclusion