The tectonic history of the Arctic Ocean remains poorly resolved and highly controversial. Details regarding break up of the Lomonosov Ridge from the Barents-Kara shelf margins and the establishment of seafloor spreading in the Cenozoic Eurasia Basin are unresolved. Significantly, the plate tectonic evolution of the Mesozoic Amerasia Basin is essentially unknown. The Arctic Ocean north of Greenland is at a critical juncture that formed at the locus of a Mesozoic three-plate setting between the Lomonosov Ridge, Greenland, and North America. In addition, the area is close to the European plate, resulting in complicated interactions between all these areas that are difficult to resolve. In 2009, the 550,000 km2 LOMGRAV aero-geophysical survey produced the first collocated gravity and magnetic measurements over the area, significantly increasing the data coverage. We present an interpretation of a new free-air gravity compilation, which reveals a regionally consistent structural grain across the Lomonosov Ridge, the Ellesmere and Lincoln Sea shelves, and the Alpha Ridge. We interpret the grain as evidence of latest Cretaceous (∼80 Ma) regional extension in response to the northward propagation of Atlantic and Labrador Sea opening into the Arctic, west of Greenland. This interpretation is consistent with coincident alkaline volcanic activity evident in the borderlands of the Lincoln Sea. We further suggest that Eurekan crustal shortening contributed to the formation of the distinct Lomonosov Ridge plateau against an important fault zone north of Greenland. Our results provide new constraints for Cretaceous–Cenozoic plate reconstructions of the Arctic.