Spatial and temporal changes in autumn Eurasian snow cover and its relationship with the Arctic Oscillation

• Main Author: Marshall, Gareth J.
• Format: Text
• Language: English
• Published: 2024
• Subjects: Arctic
• Online Access: https://doi.org/10.5194/egusphere-2024-1892; https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1892/

Previous studies have demonstrated that variations in the seasonal expansion of Eurasian snow cover (SC) can influence the following winter Arctic Oscillation (AO) and, consequently, affect mid-latitude weather. We examine changes in the extent and rate of autumn Eurasian SC advance and the temporal variability of the magnitude and sign of the SC-AO relationship. Novel aspects are (i) the use of the latest version of the 20 th Century Reanalysis (20CR), allowing analysis back to 1836; (ii) adjusting the reanalysis SC through comparison with observations; and (iii) investigating spatial variation in the frequency of significant SC-AO relationships across Eurasia. Over the past 50 years the snow advance indices (SAI) demonstrate a slowing and accelerating of snow advance in October and November ( p < 0.01), respectively, corresponding to a greater contemporaneous decrease in SC extent in October than November and thus a postponement of SC onset. The most temporally robust spatial SC-AO relationship is a longitudinal dipole such that positive (negative) relationships between October SAI and the AO are more frequent in western (eastern) Eurasia. As the sum of the two regional correlations closely matches the correlation for Eurasia as a whole, an especially strong October SAI-AO relationship occurs when the sign of the relationship in one of these regions is reversed from climatology. Future work will aim to determine the exact linkages behind this new finding in the context of contemporaneous changes in regional atmospheric circulation and snow cover and the many additional factors observed to influence the SC-AO relationship.