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

Abstract

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 northwards by increasing their spatial and temporal habitat. A large-scale shuffling of subarctic and Arctic communities is reorganizing high-latitude marine ecosystems.

Pan-Arctic marine biodiversity and species co-occurrence patterns under recent climate

“…In particular, the northward expansion of temperate marine taxa, especially along the continental margins and within the major inflow shelves in the Pacific (Bering-Chukchi seas) and Atlantic (Barents Sea) sectors has been facilitated by recent record-breaking sea ice loss and retreat, ocean warming, and enhanced productivity in the Arctic regions 8,9 . In both of these inflow shelves, poleward shifts of warm-affinity taxa and highly-migratory apex predators have promoted the borealization and consequent restructuring of the Arctic marine ecosystem, driving significant changes in the community structure, functional biogeography and biodiversity facets 6,8,10,11 .…”

“…In particular, the northward expansion of temperate marine taxa, especially along the continental margins and within the major inflow shelves in the Pacific (Bering-Chukchi seas) and Atlantic (Barents Sea) sectors has been facilitated by recent record-breaking sea ice loss and retreat, ocean warming, and enhanced productivity in the Arctic regions 8,9 . In both of these inflow shelves, poleward shifts of warm-affinity taxa and highly-migratory apex predators have promoted the borealization and consequent restructuring of the Arctic marine ecosystem, driving significant changes in the community structure, functional biogeography and biodiversity facets 6,8,10,11 . The Arctic outflow shelves (Canadian Arctic Archipelago, East Greenland shelf and Fram Strait), serving as conduits in the export of Arctic sea ice and waters to the North Atlantic Ocean, have similarly shown climatedriven changes in the phytoplankton community composition 12,13 and distribution of several keystone species supporting northern indigenous communities 14 .…”

Beluga (D. leucas), harbor porpoise (P. phocoena), and killer whale (O. orca) acoustic presence in kotzebue sound, alaska: Silence speaks volumes

“…The prevalence of killer whales has likely increased during the open water season in recent years, as suggested by several studies in U.S. Arctic waters (Clarke et al, 2013;George et al, 2017;Stafford, 2018;Willoughby et al, 2020;Stafford et al, 2022a;Stafford et al, 2022b;Willoughby et al, 2022), as well as in other regions of the Arctic Ocean (Lennert and Richard, 2017;Filatova et al, 2019;Lefort et al, 2020). This increase has been linked to the climate change induced reduction in seasonal sea ice coverage, allowing killer whales to penetrate farther into the Arctic environment and stay for longer periods of time (Higdon and Ferguson, 2009).…”

Biologically important areas II for cetaceans in U.S. and adjacent waters - Arctic region

“…Visual observations in these areas have been generally limited to the open water season (i.e., July-October) when vessel access is possible and daylight is suitable for visual observations, but passive acoustic monitoring and satellite telemetry have revealed near year-round occurrence in at least some years. As environmental conditions in the Arctic continue to dramatically alter (e.g., diminished sea ice in all seasons), the continuation of passive acoustic monitoring (e.g., Stafford et al, 2022a) and satellite telemetry studies (Citta et al, 2021) that allow for year-round data collection will be paramount. Despite the discontinuation of ASAMM visual surveys, there are several ongoing research efforts, most of which are multidisciplinary, but which include a marine mammal component.…”

“…Harbor porpoises are present in the Arctic during summer and may occur year-round in some coastal areas (Castellote et al, 2017). Killer whales are also present in the Arctic region in summer and autumn but are less frequently observed than other subarctic cetacean species (see Stafford et al, 2022a).…”