Recent work suggests that the West Spitsbergen Current, which provides the principal contribution to the Arctic Ocean of salt and sensible heat, as well as of a variety of anthropogenic tracers, is a rather complex circulation feature. North of 79°N, where the isobaths diverge markedly, the current contains two separate warm cores that follow different isobaths. The western core, carried by the offshore branch of the current, follows the western flank of the Yermak Plateau, and north of 80°N at least part of this flow detaches from the plateau, probably to contribute to the recirculation in Fram Strait. In contrast, the inshore branch follows the shelf break into the Arctic Ocean. It is this inshore branch that provides the primary focus in this paper. During the transit of the inshore waters past northwestern Spitsbergen, the core properties change primarily through vertical heat flux, which during ice-free conditions in winter is estimated to be of the order of 200 W m−2 from the core layer alone. Together with some freshening within the Arctic Ocean, this process is responsible for fully transforming the original Atlantic water into arctic intermediate water within about 600 km of Fram Strait.