On the observed connection between Arctic sea ice and Eurasian snow in relation to the winter North Atlantic Oscillation

Sea ice concentration (SIC) in the eastern Arctic and snow cover extent (SCE) over central Eurasia in late autumn have been proposed as potential predictors of the winter North Atlantic Oscillation (NAO). Here, maximum covariance analysis is used to further investigate the links between autumn SIC in the Barents-Kara Seas (BK) and SCE over Eurasia (EUR) with winter sea level pressure (SLP) in the North Atlantic-European region over 1979-2019. As shown by previous studies, the most significant covariability mode of SIC/BK is found for November. Similarly, the covariability with SCE/EUR is only statistically significant for November, not for October. Changes in temperature, specific humidity, SIC/BK and SCE/EUR in November are associated with a circulation anomaly over the Ural-Siberian region that appears as a precursor of the winter NAO; where the advection of climatological temperature/humidity by the anomalous flow is related to SCE/EUR and SIC/BK anomalies. The research leading to these results has received funding from the European Commissions H2020 projects APPLICATE (GA 727862) and PRIMAVERA (GA 641727), and the ANR Belmont RACE project (ANR-20-AORS-0002). JG-S has been supported by the Ramón y Cajal programme (RYC-2016-21181). MM has been supported by the MINECO project VOLCADEC (CGL201570177-R). JB has been supported by MINECO projects CGL2016-81828-REDT (AEI) and RTI2018-098693-B643-C32 (AEI). The authors thank Hervé Douville (CNRM/Météo-France) and Guillaume Gastineau (LOCEAN/IPSL, France) for useful discussions, and two anonymous reviewers for their valuable insights.