Atmospheric forcing on the drift of Arctic sea ice in 1989–2009

Abstract

Inter‐annual variations in Arctic sea ice drift speed (Vi) in 1989–2009 were analyzed on the basis of buoy data and atmospheric circulation indices. In the circumpolar and eastern Arctic and the Fram Strait, the annual mean Vi was best explained by the sea level pressure (SLP) difference across the Arctic Ocean along meridians 270°E and 90°E, called as the Central Arctic Index (CAI). In general, Vi was more strongly related to CAI than to the Dipole Anomaly (DA). This was because CAI is calculated across the Transpolar Drift Stream (TDS), whereas the pressure patterns affecting DA sometimes move far from TDS. CAI also has the benefit of being a simple index, insensitive to the calculation method applied, whereas DA, as the second mode of a principal component analysis, is sensitive both to the time period and area of calculations. In summer, the circulation index most important for the circumpolar mean Vi was the SLP gradient across the Fram Strait. In the Canadian Basin in winter, the Arctic Oscillation index was most important. Circulation indices explained 48% of the variance of the annual mean Viin the circumpolar Arctic, 38% in the eastern Arctic, and 25% in the Canadian Basin. The local air‐ice momentum flux (τ) was always better than the 10 m wind speed in explaining Vi, but τ outperformed the circulation indices only in the Fram Strait. Atmospheric forcing did not explain the increasing trend in Vi in the period 1989–2009.