Eurasian autumn snow impact on winter North Atlantic Oscillation depends on cryospheric variability

• Main Authors: Wegmann, Martin, Rohrer, Marco, Santolaria-Otín, María, Lohmann, Gerrit
• Format: Text
• Language: English
• Published: 2019
• Subjects: Kara Sea; North Atlantic; North Atlantic oscillation; Sea ice
• Online Access: https://doi.org/10.5194/esd-2019-68; https://www.earth-syst-dynam-discuss.net/esd-2019-68/

In recent years, many components of the connection between Eurasian autumn snow cover and wintertime North Atlantic Oscillation (NAO) were investigated, suggesting that November snow cover distribution has strong prediction power for the upcoming Northern Hemisphere winter climate. However, non-stationarity of this relationship could impact its use for prediction routines. Here we use snow products from long-term reanalyses to investigate interannual and interdecadal links between autumnal snow cover and atmospheric conditions in winter. We find evidence for a negative NAO tendency after November with a strong west-to-east snow cover gradient, which is valid throughout the last 150 years. This correlation is linked with a consistent impact of November snow on a slowed stratospheric polar vortex. Nevertheless, interdecadal variability for this relationship shows episodes of decreased correlation power, which co-occur with episodes of low variability in the November snow index. We find that the same is also true for sea ice as an NAO predictor. The snow dipole itself is associated with reduced Barents-Kara sea ice concentration, increased Ural blocking frequency and negative temperature anomalies in eastern Eurasia. Increased sea ice variability in recent years is linked to increased snow variability, thus increasing its power in predicting the winter NAO.