Impact of 2007 and 2008 Arctic ice anomalies on the atmospheric circulation: Implications for long-range predictions

The impact on the atmospheric circulation of the unprecedented Arctic sea-ice anomalies during the summers 2007 and 2008 is evaluated using the atmospheric model of the ECMWF operational seasonal forecasting system. Results show that the ice anomaly had a significant impact on the atmospheric circulation over the Euro-Atlantic Sector, characterized by a high pressure over the Arctic (Greenland) and low pressure centres over Western Europe and Northwest America. The impact is similar for the two consecutive years, and it is consistent with the observed atmospheric anomalies. Results also show that the impact of the ice is strongly dependent on the underlying sea surface temperature. Results from partial coupling experiments indicate that the sea surface temperature over the Northwest Atlantic strongly affects the mean state of atmospheric circulation over the Euro-Atlantic sector (first-order impact), and conditions the response of the atmosphere to a given ice anomaly (second-order impact). The implications of these results for seasonal and long-term predictions are discussed. Copyright (C) 2010 Royal Meteorological Society