A case study of strong winds at an Arctic front

Shallow arctic fronts frequently form at the edge of the arctic sea-ice by differential heating and cooling between sea and ice surfaces. The cooling is due to a net radiative loss over the ice, while the heating is mainly sensible as cold air flows from the ice to the warmer sea. North of the surface fronts, there is normally a low-level jet with maximum easterly winds at the top of the boundary layer. II is shown from numerical simulations of a real case, that the low-level jet can reach hurricane force when interacting with easterly winds connected to extratropical cyclones. Strong wind is found both at an arctic front over the sea some distance from the ice edge, and at a secondary front at the ice edge. When the flow is from the ice to the sea, the sensible heating of the boundary layer is almost in balance with the cold-air advection. The convergence of the sensible heat flux amounts to a heating rate of more than 10 Kelvin per hour. The fronts are maintained by cross-frontal vertical circulations.