A vast dam across the Bering Strait could stop the AMOC collapsing

It would be an engineering project of truly epic scale, but we may one day have to consider building a dam between Alaska and eastern Russia. The bold proposal would aim to avoid the worst consequences of the collapse of a vital ocean current, and researchers considered it this week at a major conference.

The idea comes from Jelle Soons and his colleague Henk Dijkstra at Utrecht University in the Netherlands, who study the Atlantic meridional overturning circulation, or AMOC. This current system, which includes the Gulf Stream, is one of the main reasons why Northern Europe enjoys a relatively mild climate for its latitude.

However, we know that the current is weakening. There is great uncertainty about what would happen in the event of a collapse, but some models suggest that temperatures in northern Europe could drop significantly.

Soons thought a dam might be a possible intervention after learning that during the Pliocene Epoch, about 5.3 to 2.6 million years ago, sea levels were lower and there was a land bridge where the Bering Strait is today. Simulations of the Pliocene climate show that the AMOC was stronger then, mainly because of this land bridge. “I was like, OK, can we do this again?” Soons said.

To study the effects of building such a dam, Soons and Dijkstra ran simulations of the AMOC by varying both the date the dam would be built and the exact amount of fresh water present.

Fresh water is a key part of the equation because it currently flows from the Pacific via the Bering Strait to the North Atlantic, weakening the AMOC. Building a dam would stop or slow the flow.

In work published a few weeks ago, Soons and Dijkstra found mixed results: In some scenarios, the dam appeared to strengthen the AMOC, but in others it had the opposite effect. However, these results came from a relatively simple, low-resolution model.

On May 5, at the general assembly of the European Geosciences Union in Vienna, Austria, Soons presented work repeating the simulations on a supercomputer using a much more advanced climate model. This indicates that closing the strait would strengthen the AMOC, especially if the dam is built early – at least by 2050. “I was surprised by the strength of the recovery,” Soons says.

The Bering Strait is only 59 meters deep at its deepest point and there are two small islands in the middle, meaning any barrier could potentially be built in two halves. Ed McCann, former president of the Institution of Civil Engineers and now with Expedition Engineering, says the best way to achieve this would be to avoid concrete and instead use floating machinery to build a barrier of dredged rock and sand. “This type of construction is quite simple, but very large and very expensive,” he wrote in an email.

Jonathan Rosser, of the London School of Economics, says the work is interesting but because we don’t fully understand AMOC we can’t be sure of the consequences of such intervention. “These drastic measures really carry great uncertainties.”

Soons agrees and says that while building a dam could help in northern Europe, it could create other problems, such as changing rainfall patterns, elsewhere. “Do you consider this proposal serious? I don’t think we’re there yet,” he said.

This is not the first time that researchers have considered the idea of ​​building a huge sea dam to mitigate climate change. In 2020, Sjoerd Groeskamp of the Royal Netherlands Institute for Maritime Research unveiled an idea called the North European Barrier Barrage, which would involve building two barriers to enclose the sea between the UK and Europe and prevent rising sea levels from flooding low-lying parts of the continent.

In addition to the effects on climate, such a dam would have other side effects on things like marine mammal migrations, tides and shipping to remote communities. Soons says he toyed with ideas like building a half barrier or lowering it to a depth of just 10 meters. These are “interesting ideas,” he says, although he has not yet had a chance to properly assess their merits.