Early 21st Century Anomalously Cold Central Eurasian Winters Forced By Arctic Sea Ice Retreat in an Atmosphere Model

Abstract:

The early 21^st century was marked by several severe winters over Central Eurasia linked to a blocking anti-cyclone centered south of the Barents Sea (BS). The increased occurrence of such anomalously cold winters coincided with a strong reduction of winter Arctic sea ice cover (ASIC), especially in the BS where sea ice area exhibited a step-like decline in 2005, suggesting a possible connection. To study the possible link we performed simulations with a high-resolution global atmospheric general circulation model forced by a set of multi-year sea ice anomalies observed during the last decades. The regional circulation response to reduced ASIC in 2005-2012 exhibits a statistically significant anti-cyclonic surface pressure anomaly and a surface temperature response similar to that observed. The results suggest that the recent BS sea ice reduction may have been responsible for the recent anomalously cold winters in Central Eurasia. Furthermore, a positive sea ice anomaly in the late 1960s associated with negative phase of the North Atlantic Oscillation also results in a similar anti-cyclonic anomaly and a cooling over the continent in the model. This implies that the atmospheric circulation response to sea ice anomalies during the period of modern sea ice decline can be essentially non-linear, both with respect to amplitude and pattern.