Mantle thermal structure at northern Mid–Atlantic ridge from improved numerical methods and boundary conditions

Abstract

Summary We computed mantle flow and thermal structure beneath a segment of the northern Mid-Atlantic ridge using numerical simulations adopting asymmetric spreading and ridge migration as boundary conditions. The objective is to obtain new insights on mantle processes acting at this ridge segment. We explored different lateral boundary conditions based on velocity, stress and stress-velocity constraints highlighting differences in the depth of the thermal base of the lithosphere versus domain width. Here, we propose a new formulation of lateral and bottom boundary conditions based on the choice of a proper tangential stress at the bottom and on lateral boundaries of the domain accounting for ridge migration. Moreover, dimensional analysis of governing equations suggests that heat generation due to work of the viscous forces cannot be neglected in the computations. Therefore, we included this thermal contribution into the numerical experiments providing an application to the northern Mid-Atlantic ridge at the reference latitude of 43 ○N. Results are compared with available geophysical data in the area, including also mantle tomography models. Asymmetric spreading and ridge migration in numerical modelling account for an asymmetric accretion of the oceanic lithosphere, supporting the evidence of the asymmetries described by geophysical data across the northern Mid-Atlantic ridge segments.