Arctic Sea-ice and Patterns of the Northern Hemisphere Atmospheric Circulation

Over the past half century the Arctic has warmed at about twice the global rate (Arctic amplification) with important and worrying sea-ice declining in the region (around 4% per decade in the year but more than 10% per decade in the summer). As the climate continues to warm further reduction are expected: coupled model projections suggests that perennial Arctic sea-ice could disappear within the next few decades. Because of the importance of the sea-ice in modulating the energy in the climate system and the associated possible effects on the global atmospheric circulation, the understanding and quantification of the sea-ice changes is crucial for climate predictions. Of particular interest is the understanding of the effects of Arctic sea-ice reductions on the winter climate of Europe, North America and parts of Asia. The ocean-atmosphere coupling has been found important for the simulation of the response to sea-ice but the climatological background state could be crucial as well, as it may play a key role in the North Atlantic Oscillation (NAO) response to reduced Arctic sea-ice. Still there is no consensus even on the sign of the NAO response in different models and experimental setup. With a statistical approach we intend to investigate the relationship between the Arctic sea-ice and the main circulation patterns of the Northern Hemisphere winter (i.e. NAO, Arctic Oscillation and Pacific North American pattern). Lagged-time analyses as well as simultaneous teleconnections are considered to explore the influence of the minimum coverage in the Arctic (September) on the winter following, but also the effects of the main winter regimes on the Arctic sea-ice. A suite of atmospheric model experiments with prescribed sea-ice together with coupled model experiments complement the finding from atmospheric reanalysis and observations. Implications and aspects of predictability for winter sea-ice conditions and related atmospheric circulation are discussed.