Eurasian cooling in response to Arctic sea-ice loss is not proved by maximum covariance analysis

• Main Authors: Zappa, Giuseppe, Shepherd, Theodore G., Ceppi, Paulo
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: arXiv 2019
• Subjects: Atmospheric and Oceanic Physics physics.ao-ph; FOS Physical sciences; Arctic; Sea ice
• Online Access: https://dx.doi.org/10.48550/arxiv.1911.10777; https://arxiv.org/abs/1911.10777

The extent to which the ongoing decline in Arctic sea ice affects mid-latitude climate has received great attention and polarised opinions. The basic issue is whether the inter-annual variability in Arctic sea ice is the cause of, or the response to, variability in mid-latitude atmospheric circulation. A recent paper by Mori et al. (M19) claims to have reconciled previous conflicting studies by showing that a consistent mid-latitude climate response to inter-annual sea-ice anomalies can be identified in both the ERA-Interim reanalysis, taken as observations, and in an ensemble of atmosphere-only (AMIP) climate model simulations. We here demonstrate that such a conclusion cannot be drawn, due to issues with the interpretation of the maximum covariance analysis performed. After applying the M19 approach to the output from a simple statistical model, we conclude that a predominant atmospheric forcing of the sea-ice variability, rather than the converse, is the most plausible explanation of the results presented in M19.