The panarctic region is tightly connected to subarctic regions by through‐flowing Atlantic and Pacific water masses and, as such, local changes in ice cover, ocean properties and ecosystem dynamics cannot be fully understood separately from large‐scale oceanographic structures and advective processes. The Canadian International Polar Year (IPY) project Canada's Three Oceans (C3O) and the related Joint Ocean Ice Study (JOIS) have collected oceanographic data along a transit extending around northern North America to establish an initial, large‐scale baseline against which present and future changes can be gauged. Special focus was given to the shelf and the basin regions of the Canada Basin and the Canadian Arctic Archipelago. We use the first results from physical and geochemical data obtained during the summer of 2007 to discuss linkages between the Arctic and Subarctic domains and trace the cascade of key processes that affect contemporary ocean structure. A review of the literature, combined with these observations, is used to identify early signs of ongoing change throughout the three oceans surrounding northern North America including ocean warming and freshening, sea‐ice melting, increased hypoxia, reduced pH and altered biogeography.