Ekman spiral . A theoretical, graphic description of the way in which a wind, blowing uniformly and steadily over a homogeneous ocean of unlimited depth and extent and of constant viscosity, would cause currents in the surface layers to vary with depth, the water at the very surface drifting at an angle of 45° to the right of the wind direction in the Northern Hemisphere (and to the left in the Southern Hemisphere) and water at successive depths drifting in directions farther away from the wind direction (as a spiral) with a rapidly decreasing speed until it would move in the direction opposite to the wind; the net water transport (Ekman transport) is 90° to the right of the wind direction in the Northern Hemisphere. It is named for Vagn Walfrid Ekman, Swedish oceanographer, who in 1902 developed the theory of the spiral, which has also been applied to atmospheric motion.