Seafloor asymmetry in the Atlantic Ocean

Measurements of seafloor asymmetry at about 360 000 pairs of conjugate points along 1250 profiles across the mid-Atlantic Ridge (MAR) provide new constraints on models for the upwelling of the buoyant asthenosphere. The sign and amplitude of the asymmetry vary systematically and are functions of the distance between the spreading center and the location of the inferred location of maximum regional buoyancy (LMRB) in the asthenosphere. The LMRB is a smooth line derived from the observed asymmetry and is more centered at the regional topographic high than the spreading center. These observations are best explained by active upwelling of the underlying buoyant asthenosphere rather than by pressure-release melting.