Interannual variations in the Beaufort Sea summer ice cover influence climatic, ecological, and socioeconomic conditions. Utilizing an ice severity index based on the distance from Point Barrow, Alaska, to the ice edge and characteristics of the shipping season, variations in summer ice conditions are examined from 1953 through 2000 with respect to variations in winter and summer surface and meteorological conditions. Although there is no significant trend in the ice severity index, ice conditions during the 1990s were less severe than in previous decades. Interannual variations in summer ice conditions are related to dynamical mechanisms in the preceding winter and dynamical and thermodynamical processes during summer. In winters preceding light ice summers, high pressure develops over Siberia, leading to increased ice transport across the Transpolar Drift Stream, while the Beaufort Gyre is diminished, resulting in decreased multiyear ice transport into the Beaufort Sea. Air temperatures are also elevated near the Alaskan North Slope, but there is little difference in winter air temperature over the Beaufort Sea. During light ice summers the Beaufort High is strongly defined over the Canadian Arctic Archipelago, enhancing easterly and northerly winds and advecting sea ice out of the Beaufort Sea. Above-normal air temperatures also occur over much of the southern Beaufort Sea. Variations in sea level pressure and winds that result in light and heavy ice summers are closely linked to positive and negative winter Arctic Oscillation/North Atlantic Oscillation phases, as well as negative and positive summer Arctic Oscillation/North Atlantic Oscillation phases.