Evolution of the Arctic Ocean lithosphere has involved multiple stages of opening with crustal stretching and thinning prior to lithospheric breakup. Mapping lateral variations in lithospheric rheology can help unravel the detailed tectonic history of the Arctic. Here we perform a wavelet analysis of gravity and bathymetry data to map the effective elastic thickness (Te) of the lithosphere in the Arctic. The low overall Te suggests that large shear stresses and serpentinization weakened the lithosphere at Arctic passive margins during a multistage opening process. Moderately low Te values along the Gakkel Ridge imply a relatively cold ultraslow-spreading center compared to typical mid-ocean ridges.