Theoretical model to explain the currents that would result from a steady wind blowing over an ocean of unlimited depth and extent. In the northern hemisphere the surface layer of the water would flow at an angle of 45° to the right of the wind direction. Water at increasing depths would flow in directions more to the right, until, at a depth known as the Ekman depth, the water would move in a direction opposite to that of the wind. The Ekman depth varies with latitude and wind speed, ranging from about 45 m in latitude 45° with a wind speed of 5 m/s, to 300 m at latitude 15° with a wind speed of 20 m/s. The velocity of the water flow decreases with depth throughout the spiral. In the northern hemisphere, the net water transport is at 90° to the right of the wind direction, and is known as the Ekman transport.