8 Minutes
A radical ocean geoengineering idea
At the 80-kilometre-wide Bering Strait between Russia and Alaska, scientists have proposed an unconventional geoengineering strategy: construct a large dam across the channel to alter ocean flows and protect the Atlantic Meridional Overturning Circulation (AMOC). The AMOC is a system of surface and deep currents that transports warm, salty water northward in the Atlantic and returns cold water southward at depth. That circulation helps moderate Western Europe’s climate and plays a central role in global heat and carbon transport.
Proponents argue that, under some warming scenarios, large volumes of freshwater and rapid ocean warming could weaken or even collapse the AMOC. In a simple modeling experiment published as an arXiv preprint, researchers Jelle Soons (a doctoral student at Utrecht University) and Henk Dijkstra suggest that blocking Pacific inflow through the Bering Strait could reduce the fresh-water pressure on the North Atlantic and thereby strengthen or stabilize the AMOC. As Soons puts it: 'The risk of collapse is certainly not negligible.'
At the same time, critics warn that closing the strait could introduce new, poorly understood feedbacks and harms. 'The feedbacks and consequences of this are enormous and enormously unknown,' says Susan Lozier, an oceanographer at the Georgia Institute of Technology. Earlier and more detailed simulations by other groups have reached the opposite conclusion: that sealing the strait could actually trigger the very collapse the dam is intended to prevent.
Scientific background: why the AMOC matters
The Atlantic Meridional Overturning Circulation (AMOC) is often described as a global conveyor belt. Warm, salty surface waters flow northward from the tropics toward the North Atlantic; there they cool, increase in density, and sink into the deep ocean, returning equatorward at depth. This overturning moves heat and carbon and helps maintain regional climate patterns.
Climate scientists identify two pathways by which anthropogenic warming could weaken or stall the AMOC. First, direct surface warming in the North Atlantic can reduce the capacity of surface water to cool and sink. Second, added freshwater from melting ice sheets and increased precipitation lowers surface salinity and buoyancy, preventing sinking. Both mechanisms reduce deepwater formation and can slow the overturning.
Paleoclimate records show that during past glacial periods — when sea level was lower and the Bering land bridge closed the connection between the Arctic and Pacific — the AMOC was different, and possibly stronger. That geological precedent motivates the idea of artificially recreating a Bering barrier today as a deliberate intervention to influence ocean circulation.
Models disagree: stabilizer or trigger?
Soons and Dijkstra’s simplified model emphasizes rapid warming and the role of Pacific-origin freshwater entering the Arctic and flowing into the North Atlantic through the strait. In their simulations, that Pacific-sourced, relatively fresh water travels through the Arctic and then into the North Atlantic where it contributes to freshening and collapse. Blocking the strait reduced that pathway and helped preserve overturning in their runs.
However, more sophisticated earlier work — notably from Aixue Hu at the National Center for Atmospheric Research and other groups — produced contrasting results. Hu’s models focused on freshwater inputs directly into the North Atlantic and found that some of that fresh water travels into the Arctic and then escapes to the Pacific through the Bering Strait. In that framing, the strait acts as a safety valve: letting freshwater out of the Atlantic system can help maintain North Atlantic salinity and the AMOC. Close the strait, Hu found, and freshwater accumulates in the Arctic until it eventually flows back into the Atlantic and triggers a sudden circulation shutdown.
Hu has summarized this contrast succinctly: 'It’s an interesting idea. But in reality, it could cause the potential problem they are trying to avoid.' Other ocean modelers have reported similar safety-valve dynamics in their simulations. As Susan Lozier emphasizes: 'Climate models that predict tipping points have no validation.' That uncertainty — different models, different parametrizations of mixing, sea ice, and freshwater routing — means the engineering idea requires far more detailed, multi-model evaluation before any serious consideration of implementation.
A simplified view of the Atlantic Meridional Overturning Circulation, which ferries warm water to Western Europe before cooling and sinking to the ocean floorMIKKEL JUUL JENSEN/SCIENCE PHOTO LIBRARY
Engineering feasibility, ecological consequences and geopolitics
From an engineering viewpoint the Bering Strait is not impossibly large. At its narrowest point Russia and Alaska are closer together than some major city pairs; the maximum depth is about 59 metres and two small islands lie mid-channel. The Saemangeum Seawall in South Korea, 33 kilometres long and up to 54 metres deep, demonstrates that large coastal barriers can be built at multi-billion-dollar cost. That seawall cost nearly $3 billion and was completed in relatively calm, accessible coastal waters — not in a remote Arctic strait subject to sea ice, strong storms and complex international politics.
Environmental and social consequences would be substantial. The strait is a seasonal migration route for marine mammals and many fish species; it also provides habitat for subarctic species expanding northward as the Arctic warms. Disrupting these pathways would affect Indigenous coastal communities that depend on marine resources for food security, cultural practices and local economies. The barrier could also impede an increasing volume of commercial shipping and create new navigational and logistical hazards.
Beyond local impacts, the dam could reconfigure regional ocean currents, sea-ice patterns, and nutrient delivery across the Arctic and North Pacific, producing cascading effects on ecosystems and fisheries. Given the multi-decadal response times of the ocean, unintended consequences might unfold slowly and be difficult to reverse.
Soons is currently testing the Bering-dam scenarios in more advanced climate models to check the robustness of his initial findings. For now, critics argue these preliminary results are insufficient to justify any engineering action. As Aixue Hu notes bluntly: 'This work alone cannot convince us to do this.'
Alternatives and complementary approaches
Some scientists suggest less invasive interventions if the goal is to maintain ocean density and overturning — for example, localized 'salting' of the North Atlantic to increase surface salinity and density, though such proposals also raise serious ethical, logistical and ecological questions. Most climate scientists emphasize that the primary and most effective strategy remains deep emissions reductions: slowing global warming by cutting fossil-fuel use reduces the risk of large-scale changes to ocean circulation in the first place.
Expert Insight
Dr. Elena Cortés, a senior physical oceanographer at the Arctic Climate Institute, provides a practical perspective: 'The Bering-dam idea is bold and intellectually interesting because it links paleoclimate evidence with potential future interventions. But oceans are highly interconnected. Models disagree for a reason: different representations of sea ice, mixing, and freshwater pathways lead to different outcomes. Before even contemplating construction, we need coordinated multi-model intercomparisons, regional high-resolution simulations, ecological impact assessments, and meaningful engagement with Indigenous and coastal communities. Engineering solutions to climate risks cannot be divorced from social, ecological and geopolitical realities.'
Conclusion
Blocking the Bering Strait with a dam is a provocative geoengineering proposal that highlights both the fragility and complexity of Earth’s ocean systems. Simple models suggest it could help stabilize the Atlantic Meridional Overturning Circulation under some scenarios, while more detailed simulations warn it could instead trigger the collapse it aims to prevent. Technical feasibility is plausible, but environmental, social and geopolitical costs are large and deeply uncertain. Most experts agree that far more modeling, ecological study and stakeholder consultation would be required before any real-world consideration — and that the most reliable route to protecting ocean circulation remains rapid, sustained reductions in greenhouse gas emissions.
Comments