Effective elastic thickness of North Atlantic lithosphere reveals weakened continental margins and mid-ocean ridge

In this paper， we quantify long-term flexural strength and flexure rigidity of the entire North Atlantic lithosphere by estimating its effective elastic thickness T_e using squared real Bouguer coherence. The spatial variation of T_e is found well correlated with the tectonic settings and/or oceanic crustal age. T_e are low at the mid-ocean ridge and some magmatic features， indicating a geothermal weakening on the lithosphere. Excluding the continental margin area， T_e shows a generally negative correlation with heat flow and positive correlation with Curie-point depth， again supporting a strong thermal control on T_e. Whereas， low T_e at cold and old continental margins indicate a greater influence by tectonics that have weakened the north Atlantic continental margins. The regionally maximum T_e occurring in the Puerto Rico Trench is possibly due to plate motion， internal loads and subduction-induced dynamic topography. We argue that the internal strength of oceanic lithosphere is primarily controlled by the temperature， but in the continental margin area， the lithospheric strength is influenced by seamount loading， stretching and serpentinization， and inception of dynamic subduction. Continental margin weakening could facilitate future induced subduction initiation.