Northward Range Expansion of Subarctic Upper Trophic Level Animals into the Pacific Arctic Region

Studies of the impacts of climate change on Arctic marine ecosystems have largely centered on endemic species and ecosystems, and the people who rely on them. Fewer studies have focused on the northward expansion of upper trophic level (UTL) subarctic species. We provide an overview of changes in the temporal and spatial distributions of subarctic fish, birds, and cetaceans, with a focus on the Pacific Arctic Region. Increasing water temperatures throughout the Arctic have increased "thermal habitat" for subarctic fish species, resulting in northward shifts of species including walleye pollock and pink salmon. Ecosystem changes are altering the community composition and species richness of seabirds in the Arctic, as water temperatures change the available prey field, which dictates the presence of planktivorous versus piscivorous seabird species. Finally, subarctic whales, among them killer and humpback whales, are arriving earlier, staying later, and moving consistently farther north, as evidenced by aerial survey and acoustic detections. Increasing ice-free habitat and changes in water mass distributions in the Arctic are altering the underlying prey structure, drawing UTL species northward by increasing their spatial and temporal habitat. A large-scale shuffling of subarctic and Arctic communities is reorganizing high-latitude marine ecosystems.