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Climate change impacts are pronounced at high latitudes, where warming, reduced sea-ice-cover, and ocean acidification affect marine ecosystems. We review climate change impacts on two major gateways into the Arctic: the Bering and Chukchi seas in the Pacific and the Barents Sea and Fram Strait in the Atlantic. We present scenarios of how changes in the physical environment and prey resources may affect commercial fish populations and fisheries in these high-latitude systems to help managers and stakeholders think about possible futures. Predicted impacts include shifts in the spatial distribution of boreal species, a shift from larger, lipid-rich zooplankton to smaller, less nutritious prey, with detrimental effects on fishes that depend on high-lipid prey for overwinter survival, shifts from benthic- to pelagic-dominated food webs with implications for upper trophic levels, and reduced survival of commercially important shellfish in waters that are increasingly acidic. Predicted changes are expected to result in disruptions to existing fisheries, the emergence of new fisheries, new challenges for managing transboundary stocks, and possible conflicts among resource users. Some impacts may be irreversible, more severe, or occur more frequently under anthropogenic climate change than impacts associated with natural variability, posing additional management challenges.

We review recent trends and projected future physical and chemical changes under climate change in transition zones between Arctic and Subarctic regions with a focus on the two major inflow gateways to the Arctic, one in the Pacific (i.e. Bering Sea, Bering Strait, and the Chukchi Sea) and the other in the Atlantic (i.e. Fram Strait and the Barents Sea). Sea-ice coverage in the gateways has been disappearing during the last few decades. Projected higher air and sea temperatures in these gateways in the future will further reduce sea ice, and cause its later formation and earlier retreat. An intensification of the hydrological cycle will result in less snow, more rain, and increased river runoff. Ocean temperatures are projected to increase, leading to higher heat fluxes through the gateways. Increased upwelling at the Arctic continental shelf is expected as sea ice retreats. The pH of the water will decline as more atmospheric CO2 is absorbed. Long-term surface nutrient levels in the gateways will likely decrease due to increased stratification and reduced vertical mixing. Some effects of these environmental changes on humans in Arctic coastal communities are also presented.