Two circulation regimes of the wind-driven Arctic Ocean

The major goal of this paper is to demonstrate the existence in the Arctic Ocean of two regimes of wind-forced circulation. We simulated the vertically averaged currents, sea level heights, and ice drift in the Arctic Ocean from 1946 to 1993 using a two-dimensional, wind-forced, barotropic model that includes frictional coupling between the ocean and ice. The model has a spatial resolution of 55.5 km and is driven by winds, river runoff, and an imposed but realistic sea level slope between the Pacific and the Atlantic Oceans. There is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics. The results indicate that wind-driven motion in the central Arctic alternates between anticyclonic and cyclonic circulation, with each regime persisting for 5–7 years, based upon our analysis of the modeled sea level and ice motion. Anticyclonic wind-driven motion in the central Arctic appeared during 1946–1952, 1958–1963, 1972–1979, and 1984–1988, and cyclonic motion appeared during 1953–1957, 1964–1971, 1980–1983, and 1989–1993. Shifts from one regime to another are forced by changes in the location and intensity of the Icelandic low and the Siberian high. The two regimes may help explain the significant, basin-scale changes in the Arctic's temperature and salinity structure observed recently, the Great Salinity Anomaly, and the variability of ice conditions in the Arctic Ocean.