The Subarctic and Arctic seas of the Northern Hemisphere contain productive ecosystems teeming with fish, shellfish, birds, sea mammals and seaweeds. These waters support coastal communities and productive industrial fisheries today, but things are changing. As climate warms, taxa are moving north, reassembling in new ecological configurations and transforming food webs. These developments, while novel in comparison to the past century, are not unprecedented. Human residents of the surrounding coasts have made their livings from these waters for millennia and have witnessed and adapted to changes in these systems before. As archaeologists, historical ecologists, historians, paleoecologists and paleoceanographers, the authors in this special issue have dedicated their careers to documenting past changes in these coupled natural and human ecosystems. As contributors to the Paleoecology of Subarctic and Arctic Seas (PESAS) working group, they seek to better understand the histories of environmental change and human adaptation in the subarctic and Arctic maritime environment both for its own sake and for the lessons it can offer in confronting the socio-ecological challenges of the present and anticipated future.