The summer Arctic sea ice extent (SIE) during the period 1996-2008 had an accelerating trend of retreat. The difference of SIE between May and September has a significant correlation with the summer Northern Hemisphere Annular Mode (summer NAM). The summer NAM had a significant positive trend during the period 1958-1996, and a weak negative trend during the period 1996-2008. The atmospheric circulation during the recent period had a trend of anticyclonic circulation over the Arctic with easterly wind over the marginal seas. In addition, tropospheric warming was enhanced especially over the Arctic and near the ground surface.