|Title||Impact of 2007 and 2008 Arctic ice anomalies on the atmospheric circulation: Implications for long-range predictions|
|Publication Type||Technical memorandum|
|Secondary Title||ECMWF Technical Memoranda|
|Authors||Alonso-Balmaseda, M, Ferranti, L, Molteni, F, Palmer, TN|
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 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 North-West 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 mean atmospheric circulation and on the underlying sea surface temperature. Results from partial coupling experiments indicate that the sea surface temperature over the North West Atlantic determines the mean atmospheric circulation over the Euro-Atlantic Sector (first order impact), and conditions (but not determine) 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.