Abstract
Abstract. The authors present an analytical model for wind-driven free drift of sea ice that allows for an arbitrary mixture of ice and open water. The model includes an ice–ocean boundary layer with an Ekman spiral, forced by transfers of wind-input momentum both through the sea ice and directly into the open water between the ice floes. The analytical tractability of this model allows efficient calculation of the ice velocity provided that the surface wind field is known and that the ocean geostrophic velocity is relatively weak. The model predicts that variations in the ice thickness or concentration should substantially modify the rotation of the velocity between the 10 m winds, the sea ice, and the ocean. Compared to recent observational data from the first ice-tethered profiler with a velocity sensor (ITP-V), the model is able to capture the dependencies of the ice speed and the wind/ice/ocean turning angles on the wind speed. The model is used to derive responses to intensified southerlies on Arctic summer sea ice concentration, and the results are shown to compare closely with satellite observations.
Highlights
The drift of Arctic sea ice is largely explained by surface winds and upper-ocean currents
The role of the winds becomes increasingly important over shorter timescales: on timescales from days to months, surface wind variability explains more than 70 % of the sea ice motion (Thorndike and Colony, 1982) and is well correlated with the surface ocean velocity (Cole et al, 2014)
We suggest that the reduction of sea ice concentration (SIC) is caused by the southerly windinduced sea ice drift
Summary
The drift of Arctic sea ice is largely explained by surface winds and upper-ocean currents. Many simple sea ice models assume steady ocean currents and prescribe a quadratic relationship with an empirically chosen turning angle between the ice stress and surface ocean velocity (Hibler III, 1979; Thorndike and Colony, 1982; Bitz et al, 2002; Uotila et al, 2012). This model configuration has limitations in simulating wind-induced sea ice drift on intraseasonal timescales, during which time-varying Ekman layer flows in the ice–ocean boundary layer (IOBL) may be important. Such an approach is computationally expensive and makes it difficult to disentangle the physical processes controlling sea ice drift
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