Building a giant dam between Russia and Alaska might save a key Atlantic current that is crucial to regulating the climate in northern Europe. However, that massive undertaking presents other risks, researchers explain in a new study.

By stretching across the Bering Strait and disconnecting the Pacific Ocean from the Arctic Ocean, this huge geoengineering scheme could buy more time for the threatened conveyor belt of currents known as the Atlantic Meridional Overturning Circulation (AMOC), according to the study. However, the study authors and other researchers caution that the effect is variable, the results are preliminary, and further modeling studies are needed to see if such a bold course of action might be merited.

Impending AMOC collapse

The AMOC moves warm, salty water from the tropics northward, where it cools and sinks, and shifts cold water south, sustaining marine life and regulating the climate across Europe, Africa and the Americas. It is why Europe has a relatively mild climate despite its high latitude.

Numerous studies have suggested that the AMOC is weakening and may collapse. Research published earlier this month says it will slow down between 43% and 59% by 2100 — a 60% stronger weakening than past models predicted — so it may be closer to collapse than previously thought. If it does fail, the consequences could be catastrophic, causing temperatures in Northern Europe to plummet, bringing drought, raising the sea level along the northeast coast of North America by at least 1.6 feet (50 centimeters), as well as disrupting food production.

"The evidence is pointing towards collapse, but it's very uncertain," lead author Jelle Soons, a researcher who studies the AMOC at the Institute for Marine and Atmospheric Research at Utrecht University in the Netherlands, told Live Science.

There are two ways global warming could stop the AMOC. One possibility is that warmer North Atlantic waters could prevent the warm, salty water it is carrying from cooling and sinking. Another is that melting ice sheets in the North could add more fresh water to the mix, thereby diluting the saltiness of the arriving water and stopping it from sinking.

Previous research showed that the AMOC was stronger in the mid-Pliocene some 3 million years ago, primarily because there was a land bridge closing off the Bering Strait. "So I wondered what would happen if we closed off the Bering Strait again," Soons said.

Three dams across the strait

In the new study, published Friday (April 24) in the journal Science Advances, Soons and his colleague Henk Dijkstra, a physical oceanographer at the Institute for Marine and Atmospheric Research, modeled what would happen if that passage were closed. First, it would require three dams to cover the 51-mile-wide (82 kilometers) stretch of water, because two islands sit in the middle of the strait. The longest would need to be about 24 miles (38 km) in length.

They found that with lower levels of carbon dioxide (CO₂) emissions and a minor weakening of the AMOC, the closure of the Bering Strait could strengthen the AMOC and allow it to continue to function as CO₂ emissions rise. However, they also discovered that with a much weaker AMOC, a closure of the Bering Strait would accelerate AMOC weakening.

"This means it is not a straightforward solution," Jonathan Baker, an ocean scientist at the U.K. Met Office who wasn't involved in the study, told Live Science in an email. This means a dam might put off AMOC collapse only in some situations, he added.

The result is very interesting and provides an alternative way to mitigate the effects of rising CO₂ levels, said Aixue Hu, an oceanographer at the National Center for Atmospheric Research who wasn't involved in the work.

"However, the overall effect is not consistent and highly depends on the AMOC strength and CO₂ levels," Hu told Live Science via email. "Even if the closure of the Bering Strait can strengthen the AMOC and allow for more CO₂ emissions in the near future, the long-term effect is still uncertain."

The engineering of a Bering Strait dam should be technically feasible, Soons said. The longer parts wouldn't be much longer than the Afsluitdijk dam in the Netherlands, which covers 20 miles (32 km), or the Saemangeum Seawall in South Korea, which is 21 miles (33 km) long, he said. A Bering Strait dam would have a maximum depth of 194 feet (59 meters), which isn't much deeper than the deepest part of the Saemangeum Seawall, which goes down to 177 feet (54 m).

However, both of those constructions are in relatively calm coastal waters, not in remote locations with strong currents and sea ice, or with rival geopolitical powers on opposite sides.

Severing the connection between the Pacific and Arctic oceans would also affect wildlife, fishing industries, shipping and Indigenous communities who are dependent on the strait for food and trade, Soons said.

"Blocking the strait would alter the exchange of water, heat, nutrients and marine life between the Pacific and Arctic Oceans, with potential impacts on marine ecosystems and regional ocean circulation," Baker said. "It could also lead to changes in climate that are not yet fully understood. Any intervention of this scale would need to carefully consider potential unintended consequences alongside any intended benefits."

Soons, Baker and Hu all say more modeling work is needed to explore the findings and get a more detailed picture of what would happen under different scenarios.

There is also a more straightforward way to save the AMOC. "Closing the Bering Strait might delay a collapse under some conditions, but it does not remove the underlying risk from continued warming," Baker said. "The most reliable way to reduce AMOC risk remains cutting greenhouse gas emissions."

Chris Simms is a freelance journalist who previously worked at New Scientist for more than 10 years, in roles including chief subeditor and assistant news editor. He was also a senior subeditor at Nature and has a degree in zoology from Queen Mary University of London. In recent years, he has written numerous articles for New Scientist and in 2018 was shortlisted for Best Newcomer at the Association of British Science Writers awards.