Influence of dynamic topography on sea level and its rate of change

Mantle flow likely supports up to 2 km of long-wavelength topographic relief over Earth's surface. Although the average of this dynamic support must be zero, a net deflection of the ocean basins can change their volume and induce sea-level change. By calculating dynamic topography using a global mantle flow model, we find that continents preferentially conceal depressed topography associated with mantle downwelling, leading to net seafloor uplift and similar to 90 +/- 20 m of positive sea-level offset. Upwelling mantle flow is currently amplifying positive dynamic topography and causing up to 1.0 m/Ma of sea-level rise, depending on mantle viscosity. Continental motions across dynamic topography gradients also affect sea level, but uncertainty over the plate motion reference frame permits sea-level rise or fall by +/- 0.3 m/Ma, depending on net lithosphere rotation. During a complete Wilson cycle, sea level should fall during supercontinent stability and rise during periods of dispersal as mantle flow pushes continents down dynamic topography gradients toward areas of mantle downwelling. We estimate that a maximum of similar to 1 m/Ma of sea-level rise may have occurred during the most recent continental dispersal. Because this rate is comparable in magnitude to other primary sea-level change mechanisms, dynamic offset of sea level by mantle flow should be considered a potentially significant contributor to long-term sea-level change.