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Abstract:
We investigate the impact of the Barents-Kara sea ice area (SIA) loss in December on atmospheric circulation over the North Atlantic and Eurasia in December-January (DJ) and February-March (FM) using the daily 1200 UTC ERA5 data from December 1979 to March 2022. The Barents-Kara SIA loss in December contributes to an increase in geopotential height at 500 hPa (Z500), mean sea level pressure (MSLP), the frequency and intensity of blocking, and meridional gradient intensity (MGI), but a decrease in the 250-hPa zonal wind (U250) over the Ural in DJ and the high-latitude North Atlantic in FM. A negative North Atlantic Oscillation (NAO) develops in FM (particularly in mid-February) in response to the Barents-Kara SIA loss in December. The correlation between the Barents-Kara SIA loss and anomalies of both Z500 and the area of instantaneous blocking (IB) over the Ural is positive in early winter, but following the development of positive Z100 anomalies over the polar cap from mid-to-late winter, the correlation becomes negative in early spring. An increase in the area of Ural blocking induced by the Barents-Kara SIA loss precedes the initiation of positive Z100 anomalies over the polar cap by one month, and three weeks after the initiation of positive Z100 anomalies in mid-January, the IB area over the high-latitude North Atlantic reaches its maximum and the negative NAO reaches its minimum value. Positive Z500 anomalies and a decrease in the IB area over the Ural occur 0-7 and 8-12 days after a strong positive NAO event.
