Atlantification Reshapes the Barents and Kara Seas
The Barents Sea Abloom. The chlorophyll contained in phytoplankton often shows up in natural-color images as a green hue in the ocean’s surface waters. Source: NASA
In early October 2026, the Floating University expedition of the Moscow Institute of Physics and Technology (MIPT) and the Shirshov Institute of Oceanology (IO RAS) departed Arkhangelsk aboard the research vessel Ivan Petrov. The fourth voyage of the national Floating University program’s field season set course for the Kara and Laptev seas, where over two stages spanning about 46 days researchers took up three themes: ocean physics, marine biology, and marine pollution. Among the expedition’s tasks were the Atlantic waters spreading into the northern Kara Sea and the plankton and benthic communities that record how those waters are reshaping Arctic ecosystems.
THE CHANGING BARENTS SEASeries · 2 posts
- Atlantification Reshapes the Barents and Kara Seas
- The Seabed That Feeds the Barents Sea
Studying the current state of the ecosystem in the Barents and Kara seas is another task of the Floating University expedition. Biological processes are far more complex and unpredictable than the physics of the sea, so ship-based research is absolutely indispensable here. The distant overarching goal of all this biological research is to understand how the ecosystem of the Arctic seas will change under global warming, and whether it will be possible to catch more fish there. But this goal can only be approached in small steps.
The Arctic is changing rapidly under the influence of global warming. One of the most conspicuous processes of recent decades has been Atlantification—the growing influence of the warming waters of the Atlantic Ocean on the Arctic seas. These changes affect not only water temperature and the ice cover but also marine ecosystems. Following the warm waters northward, new species of organisms that had never been found there before—it was simply too cold for them—are moving in. As a result, food chains and the living conditions of native Arctic inhabitants are changing.
Biological Atlantification shows itself most vividly in the Barents Sea, whose conditions increasingly come to resemble the North Atlantic. In particular, in recent decades the range of Atlantic cod and other North Atlantic fish has been expanding in the Barents Sea.
But fish are not the only ones venturing ever farther north: the range of the Atlantic copepod species Calanus finmarchicus is also expanding in the Barents Sea.
Calanus finmarchicus. Source: iNaturalist, Leïla Brunner, CC BY 4.0. Changes were made: the lens information was cut out.
It differs from the characteristic Arctic species—in particular Calanus glacialis and Calanus hyperboreus—in the features of its life cycle and fat accumulation; previously it could not reach maturity in the cold waters of the Arctic.
Calanus hyperboreus. Source: iNaturalist, Ingvild Riska, CC BY 4.0.
Calanus glacialis. Source: iNaturalist, Philipp Byzov, CC BY-NC 4.0.
A change in the ratio of these copepods therefore affects the availability of food for fish, seabirds, and mammals.
In the Kara Sea, biological Atlantification is so far weaker because it lies even farther from the North Atlantic. The big question is when this sea too will become home to North Atlantic species.
It is worth noting that the Atlantification now underway does not directly lead to an increase in the Arctic’s biological diversity or productivity. In the coming decades, warming will lead (and is already leading) to bursts of productivity (phytoplankton “blooms”) in the northern parts of the Barents Sea and part of the Kara Sea, but this will not necessarily be accompanied by larger fish stocks and commercial catches. The main result will be a redistribution of marine biological resources: some species will expand their ranges, while others will face unfavorable conditions and new competitors for food, and will therefore shrink in numbers or retreat to colder areas.
Warming favors the northward and eastward spread of Atlantic cod, haddock, and some other commercial species. At the same time, the suitable habitats of the cold-loving polar cod are expected to shrink, along with a possible decline in the stocks of capelin, a key forage species for cod and other predators.
